AUTHORITIES CITED IN PART SECOND.
[23] Vines, Vegetable Physiology.
[24] Berichte der deutschen chemischen Gesellschaft, Band 23, S. 2136; Stone, Agricultural Science Vol. 6, p. 180. Page 59, eighth line from bottom insert “original” before “optical.” Page 60, second line from top, read d instead of l fructose.
[25] Herles, Zeitschrift des Vereins für die Rübenzucker-Industrie, 1890. S. 217.
[26] Tucker; Wiechmann; Sidersky; von Lippman; Tollens and Spencer.
[27] Bulletin No. 28, Department of Agriculture, Division of Chemistry, p. 197.
[28] Physikalisch-Chemische Tabellen, S. 42.
[29] Tucker’s Manual of Sugar Analysis, pp. 100 et seq.
[30] Vid. op. cit. supra, p. 108.
[31] Op. cit. supra, p. 109.
[32] Op. cit. supra, p. 110.
[33] Op. cit. supra, p. 114.
[34] Spencer’s Handbook for Sugar Manufacturers, p. 92.
[35] Landolt’s Handbook of the Polariscope, pp. 95 et seq.
[36] Robb, vid. op. cit. supra, p. 8.
[37] Spencer’s Handbook for Sugar Manufacturers, pp. 22 et seq. Tucker’s Manual of Sugar Analysis, pp. 120 et seq.
[38] Sidersky; Traité d’Analyse des Matières Sucrées, p. 104.
[39] Journal of the American Chemical Society, 1893. Vol. 15, p. 121.
[40] Comptes rendus, 1879. Seance du 20th Octobre 1879; Dingler’s polytechniches Journal, Band 223, S. 608.
[41] Landolt’s Handbook of the Polariscope. p. 120.
[42] Sidersky; Traité d’Analyse des Matières Sucrées, p. 97.
[43] Manual of Sugar Analysis, pp. 143 et seq.
[44] Landolt und Börnstein, Physikalisch-Chemische Tabellen. S. 460.
[45] Bulletin No. 31. Department of Agriculture, Division of Chemistry, p. 232.
[46] Zeitschrift des Vereins für die Rübenzucker-Industrie. 1870, S. 223.
[47] Tucker’s Manual of Sugar Analysis, p. 164.
[48] (bis). Gerlach, Spencer’s Handbook for Sugar Manufacturers, p. 91.
[49] Vid. op. cit. supra, p. 45.
[50] Vid. loc. et op. cit. supra.
[51] Gill; Journal of the Chemical Society, Vol. 24, 1871, p. 91.
[52] Wiley; American Chemical Journal, Vol. 6, p. 289.
[53] Vid. op. cit. supra, p. 301.
[54] Zeitschrift des Vereins für die Rübenzucker-Industrie, 1890. S. 876.
[55] Weber and McPherson; Journal of the American Chemical Society. Vol. 17, p. 320; Bulletin No. 43. Department of Agriculture, Division of Chemistry, p. 126.
[56] Zeitschrift des Vereins für die Rübenzucker-Industrie, 1888, S. 51.
[57] Vid. op. cit. supra, Ss, 699 und 763; 1890. S. 217.
[58] Bulletin de l’Association des Chimistes de Sucrerie et de Distillerie, May, 1890, p. 431.
[59] Neue Zeitschrift für Rübenzucker-Industrie, Band 19, S. 71.
[60] Journal of the Chemical Society, Transactions, Vol. 57, pp. 834, et seq.
[61] Op. cit. supra, p. 866.
[62] Op. cit. supra, 1891, p. 46.
[63] Neue Zeitschrift für Rübenzucker-Industrie, Band 19, S. 71.
[64] From γῦρος and δῦνᾶτός (δύνᾶμις).
[65] Landolt’s Handbook of the Polariscope, p. 125.
[66] Vid. op. cit. supra, pp. 48 et seq.
[67] Berichte der deutschen chemischen Gesellschaft, 1877, S. 1403.
[68] Die landwirtschaftlichen Versuchs-Stationen, Band 40, S. 307.
[69] Spencer’s Handbook for Sugar Manufacturers, p. 80; Landolt’s Handbook of the Polariscope, p. 216; Tollens’ Handbuch der Kohlenhydrate.
[70] Annalen der Chemie and Pharmacie, May, 1870.
[71] Tucker’s Manual of Sugar Analysis, p. 208.
[72] Rapport fait a la Société d’Encouragement d’Agriculture; Journal de Pharmacie et de Chimie, 1844. 3d serie, Tome 6, p. 301.
[73] Annalen der Chemie und Pharmacie, Band 39, S. 361.
[74] Jahrbücher für praktische Heilkunde, 1845, S. 509.
[75] Archives für Physiologische Heilkunde, 1848, Band 7, S 64.
[76] Rodewald and Tollens; Berichte der deutschen chemischen Gesellschaft, Band 11, S. 2076.
[77] Chemical News, Vol. 39, p. 77.
[78] The Analyst, Vol. 19, p. 181.
[79] Gaud; Bulletin de l’Association des Chimistes de Sucrerie et de Distillerie, Apr. 1895, p. 629; Comptes rendus, 1894, Tome 119, p. 604.
[80] Annalen der Chemie und Pharmacie, B. 72, S. 106.
[81] Journal of Analytical and Applied Chemistry, Vol. 4, p. 370.
[82] Wiley; Bulletin de l’Association des Chimistes de Sucrerie et de Distillerie, April, 1884.
[83] Vid. op. cit. supra, 1895, p. 642; Comptes rendus, Tome 119, 1894, p. 650.
[84] Annual Report, United States Department of Agriculture, 1879, p. 65; Zeitschrift für Analytische Chemie, Band 12, S. 296; Mohr Titrirmethode, sechste auflage, S. 508.
[85] Comptes rendus, 1894, Tome 119, p. 478.
[86] Gazetta Chimica Italiana, Tome 6, p. 322.
[87] Sidersky; Traité d’Analyse des Matières Sucrées, p. 148.
[88] Vid. op. cit. supra, p. 149.
[89] Neue Zeitschrift für die Rübenzucker-Industrie, Band 22, S. 220.
[90] Zeitschrift des Vereins für Rübenzucker-Industrie, 1889, S. 933.
[91] Vid. op. cit. supra, 1887, S. 147.
[92] Berichte der deutschen chemischen Gesellschaft, Band 23, No. 14, S. 3003; Zeitschrift des Vereins für die Rübenzucker-Industrie, 1891, S. 97.
[93] Ost; vid. op. et loc. cit. supra.
[94] Zeitschrift des Vereins für die Rübenzucker-Industrie, 1890, S. 187.
[95] Chemical News, Vol. 39, p. 77.
[96] The Analyst, 1894, p. 181.
[97] Chemical News, Vol. 71, p. 235.
[98] Journal de Pharmacie et de Chimie, 1894, Tome 30, p. 305.
[99] Pharmaceutical Journal, (3), 23, p. 208.
[100] Vid. op. cit. supra, (3), 25, p. 913.
[101] Sidersky; Bulletin de l’Association des Chimistes, Juillet, 1886 et Sept. 1888.
[102] Bodenbender and Scheller; Zeitschrift des Vereins für die Rübenzucker-Industrie, 1887, S. 138.
[103] Vid. op. cit. supra, 1889, S. 935.
[104] Ewell; Manuscript communication to author.
[105] Journal für praktische Chemie, 1880, Band 22, 46; Handbuch der Spiritusfabrication, 1890, S. 79; Zeitschrift des Vereins für die Rübenzucker-Industrie, 1879, S. 1050; Ibid, 1883, S. 769; Ibid, 1889, S. 734.
[106] Handbuch der Spiritusfabrication, 1890, 79.
[107] Wein; Tabellen zur quantitativen Bestimmung der Zuckerarten, S. 13. (The caption for the table on page 159 should read as on page 160.)
[108] Zeitschrift des Vereins für die Rübenzucker-Industrie, 1889, S. 735.
[109] Bulletin No. 43, Department of Agriculture, Division of Chemistry, p. 209.
[110] Chemiker-Zeitung, 1893, S. 548.
[111] Wein; Tabellen zur quantitativen Bestimmung der Zuckerarten, S. 35.
[112] Berichte der deutschen chemischen Gesellschaft, Band 16, S. 661.
[113] Vid. op. cit. supra, Band 22, S. 87.
[114] Chemisches Centralblatt, 1895, Band 2, S. 66.
[115] Comptes rendus; Tome 112, No. 15, p. 799.
[116] Vid. op. cit. supra, Tome 94, p. 1517.
[117] Journal of the Chemical Society, June, 1888, p. 610. (In the formulas for lactose and arabinose read H₂₂ and H₁₀ respectively.)
[118] American Chemical Journal, Vol. 11, No. 7, p. 469.
[119] Chemisches Centralblatt, 1889, No. 7.
[120] American Chemical Journal, Vol. 17, No. 7, pp. 507, 517.
[121] Comptes rendus, Tome 118, p. 426.
[122] Justus Liebig’s Annalen der Chemie, 1890. Band 257, S. 160.
[123] Journal of Analytical and Applied Chemistry, Vol. 7, pp. 68 et seq.
[124] Flint and Tollens; Berichte der deutschen chemischen Gesellschaft, Band 25, S. 2912.
[125] Vid. op. cit. supra, Band 23, S. 1751. (Read Günther.)
[126] Journal of Analytical and Applied Chemistry, Vol. 5, p. 421.
[127] Vid. op. cit. supra, p. 426.
[128] Berichte der deutschen chemischen Gesellschaft, Band 24, S. 3575.
[129] Journal of Analytical and Applied Chemistry, Vol. 7, p. 74.
[130] Chemiker-Zeitung, Band 17, 1743.
[131] Vid. op. cit. supra, Band 18, N. 51, S. 966.
[132] Monatshefte für Chemie, Band 16, S. 283; Berichte der deutschen chemischen Gesellschaft, Referate Band 28, S. 629.
[133] Papasogli; Bulletin de l’Association des Chimistes de Sucrerie et de Distillerie, Juillet 1895, p. 68.
[134] Gans und Tollens; Zeitschrift des Vereins für die Rübenzucker-Industrie, Band 38, S. 1126.
[135] Berichte der deutschen chemischen Gesellschaft, 20, S. 181; Zeitschrift des Vereins für die Rübenzucker-Industrie, 1891, S. 895.
[136] Zeitschrift des Vereins für die Rübenzucker-Industrie, 1891, S. 891.
[137] Chemiker-Zeitung, 1888, No. 2; Zeitschrift des Vereins für die Rübenzucker-Industrie, 1888, S. 347.
[138] Fischer; Berichte der deutschen chemischen Gesellschaft, Band 20, S. 821; Band 21, Ss. 988; 2631.
[139] Zeitschrift für physiologische Chemie, Band 11, S. 492.
[140] Vid. op. cit. supra, Band 12, No. 4, Ss. 355 et seq; No. 5, Ss. 377 et seq.
[141] Berichte der deutschen chemischen Gesellschaft, Band 20, S. 540.
[142] Sitzungsberichte der Mathematisch-Naturwissenschaften in Wien, Band 93, Heft 2, S. 912.
[143] Tollens; Handbuch der Kohlenhydrate; von Lippmann, Chemie der Zuckerarten.
[144] Wilder Quarter-Century Book, 1893; Abdruck aus dem Centralblatt für Bakteriologie und Parasitenkunde, Band 18, 1895, No. 1; American Journal of Medical Sciences, Sept., 1895.
[145] Griffiths, Principal Starches used as Food; Nägeli’s Beiträge zur näheren Kenntniss der Stärkegruppe.
[146] Zeitschrift für Physiologische Chemie, Band 12, Ss. 75-78.
[147] Maercker; Handbuch der Spiritusfabrikation, 1890, S. 90.
[148] Chemiker-Zeitung, Band 19, S. 1501.
[149] Paragraphs [28-32], this volume.
[150] Vol. 2, p. 204.
[151] Chemisches Centralblatt, 1877, Band 8, S. 732.
[152] Chemiker-Zeitung, Band 19, S. 1501.
[153] Vid. op. cit. supra, S. 1502; Moniteur Scientifique, 1887, p. 538.
[154] Chemiker-Zeitung, Band 19, S. 1502.
[155] Vid. op. cit. supra, 1895, S. 1727.
[156] Chemiker-Zeitung, Band 19, S. 1502.
[157] Jahresberichte der Agrikulturchemie, 1892, S. 664.
[158] Journal de Pharmacie et de Chimie, 5ᵉ, Série, Tome 25, p. 394.
[159] Journal of the American Chemical Society, Vol. 17, p. 64.
[160] Repertorium der Analytischen Chemie, 1887, S. 299.
[161] Journal of the American Chemical Society, Vol. 16, p. 726.
[162] Förschungs Berichte über Lebensmittel, Hamburg; Abs., The Analyst, Vol. 20, p. 210.
[163] Rouvier; Comptes rendus, Tome 107, pp. 272, 278; Tome 111, pp. 64, 186; Tome 120, p. 1179.
[164] Bulletin 13, Department of Agriculture, Division of Chemistry, pp. 154 et. seq.
[165] Foods, Their Composition and Analysis, p. 139.
[166] Richardson, Vid. op. cit. 142, p. 158.
[167] Principal Starches used as Food, Cirencester, Baily & Son, Market Place.
[168] Vid. op. cit. 142, pp. 158 et seq.
[169] Bulletin 44, Department of Agriculture, Division of Chemistry, p. 14.
PART THIRD.
PROCESSES FOR DETECTING AND DETERMINING SUGARS
AND STARCHES AND OTHER CARBOHYDRATES IN CRUDE
OR MANUFACTURED AGRICULTURAL PRODUCTS.
203. Introduction.—In the preceding part directions have been given for the estimation of sugars and starches in approximately pure forms. In the present part will be described the most approved methods of separating these bodies and other carbohydrates from crude agricultural products and for their chemical examination. In many respects the processes which in a small way are used for preparing samples for analysis are employed on a large scale for technical and manufacturing purposes. It is evident, however, that the following paragraphs must be confined strictly to the analytical side of the question inasmuch as anything more than mere references to technical processes would lead into wide digressions.
In the case of sugars the analyst is for the most part quite as much in need of reliable methods of extraction and preparation as of processes for analysis. With starches the matter is more simple and the chief methods of separating them for examination were necessarily described in the previous part.
Sugars in fresh plants exist almost entirely in solution. This is true of all the great sources of the sugar of commerce, viz., the palm, the maple, the sugar beet and sugar cane. This statement is also true of fruits and the natural nectar of flowers. By natural or artificial drying the sugar may be reduced to the solid or semisolid state as in the cases of raisins and honey. In certain seeds, deficient in water, sugars may possibly exist in a solid state naturally, as may be the case with sucrose in the peanut and raffinose in cotton seed.
Starches on the other hand when soluble, are probably not true starches, but they partake more or less of a dextrinoid nature. Fine starch particles occur abundantly in the juices of some plants, as for instance sorghum, where they are associated with sugar and can be obtained from the expressed juice by subsidence. But even in such a case it is not certain that the starch enters into the general circulation. It is more likely formed locally by biochemical condensation of its constituents. Starches in a soluble or semisoluble state are transported, as a rule, to the tubers or seeds of plants where they are accumulated in large quantities as a reserve food for future growth. For a study of the plant metabolism whereby starch is produced and for its histological and physiological properties the reader may consult the standard authorities on vegetable physiology.[170]
204. Sugar in the Sap of Trees.—Many trees at certain seasons of the year, carry large quantities of sugar in their sap. Among these the maple and sugar palm are preeminent. The sap is secured by cutting a pocket into the side of the tree or by boring into it and allowing the sap to run into an appropriate receptacle through a spile. The content of sugar in the sap of the maple and palm varies greatly. In some cases it falls as low as one and a half and in others rises to as much as six or seven per cent.[171] In most cases the sugar in the maple sap is pure sucrose, but towards the end of the flowing season it may undergo changes of a viscous nature due to fermentation, or inversion, forming traces of invert sugar. In this country the sap of the maple may flow freely on any warm day in winter, but the sugar season proper begins about February 15th in Southern Ohio and Indiana, and about March 25th in Vermont. It lasts from six weeks to two months. The sap flows best during moderately warm, still days, after a light freeze.
In addition to sugar the maple sap contains a trace of albuminoid matters and some malic acid combined with lime. As a rule it can be subjected to polarization without preliminary clarification.
205. Determination of Sugar in Saps.—In most cases the sap may be directly polarized in a 200 millimeter tube. Its specific gravity is obtained by a spindle or pyknometer, and the percentage of sugars taken directly from the table on [page 73], the degree brix corresponding to the sugar percentage.
On polarizing, the sugar percentage is calculated as follows:
Multiply the specific gravity of the sap by 100 and divide the product by 26.048. Divide the direct reading of the sap on the sugar scale by the quotient obtained above, and the quotient thus obtained will be the correct percentage of sugar in the original solution.
The formula is applicable for those instruments in which 26.048 grams represent the normal quantity of sugar which in 100 cubic centimeters reads 100 divisions on the scale. When other factors are used they should be substituted for 26.048 in the above formula.
The principle of the calculation is based on the weight of the sap which is contained in 100 cubic centimeters, and this is evidently obtained by multiplying 100 by the specific gravity of the sap. Since 26.048 is the normal quantity of sugar in that volume of the solution the quotient of the actual weight divided by that factor shows how many times too great the observed polarization is. The simple division of the polariscope reading by this factor gives the correct reading.
Example: Let the specific gravity of the sap be 1.015 and the observed polarization be 15.0. Then the true percentage of sugar in the sap is found by the equation:
101.5 : 26.048 = 15.0 : x.
Whence x = 3.85 = percentage of sugar in the sap.
The process outlined above is not applicable when a clarifying reagent such as lead subacetate or alumina cream must be used. But even in these cases it will not be found necessary to weigh the sap. A sugar flask graduated at 100 and 110 cubic centimeters is used and filled to the first mark with the sap, the specific gravity of which is known. The clarifying reagent is added, the volume completed to the second mark with water, and the contents of the flask well shaken and thrown on a dry filter. The observation tube, which should be 220 millimeters in length, is then filled with the clear filtrate and the rest of the process is as described above. A 200 millimeter tube may also be used in this case and the observed reading increased by one-tenth.
Fig. 62.
Laboratory Cane Mill.
Fig. 63.
Weighing
Pipette.
206. Estimation of Sugar in the Sap of Sugar Cane and Sorghum.—In bodies like sugar cane and sorghum the sap containing the sugar will not flow as in the cases of the maple and sugar palm. The simplest way of securing the sap of the bodies named is to subject them to pressure between rolls. A convenient method of obtaining the sap or juice is by passing the cane through a small three-roll mill indicated in the [figure]. Small mills of this kind have been used in this division for many years and with entire satisfaction. Small canes, such as sorghum, may be milled one at a time, or even two or three when they are very small. In the case of large canes, it is necessary that they be split and only half of them used at once. The mill should not be crowded by the feed in such a way as to endanger it or make it too difficult for the laborer to turn. From fifty to sixty per cent of the weight of a cane in juice may be obtained by passing it through one of these small mills. Experience has shown that there is a little difference between the juice as first expressed and the residual sap remaining in the bagasse, but the juice first expressed may be used for analysis for control purposes as a fair representative of all that the cane contains.
To determine the percentage of juice expressed, the canes may be weighed before passing through the mill and the juice collected. Its weight divided by the weight of the original cane will give the per cent of the juice expressed, calculated on the whole cane. Instead of weighing the juice the bagasse may also be collected and weighed; but on account of the rapidity with which it dries the operation should be accomplished without delay. The expressed juice is clarified with lead subacetate, filtered and polarized in the manner described in former paragraphs. Instead of weighing the juice, its specific gravity may be taken by an accurate spindle and the volume of it, equivalent to a given weight, measured from a sucrose pipette.[172]
A sucrose pipette for cane juice has a graduation on the upper part of the stem which enables the operator to deliver double the normal weight for the polariscope used, after having determined the density of the juice by means of a spindle. A graduation of from 5° to 25° of the brix spindle will be sufficient for all variations in the density of the juice, or one covering a range of from 10° to 20° will suffice for most instances. The greater the density of the juice the less volume of it will be required for the weight mentioned. For general use, the sucrose pipette is graduated on the stem to deliver from forty-eight to 50.5 cubic centimeters, the graduations being in terms of the brix spindle. The graduation of the stem of this instrument is shown in the accompanying [figure]. In the use of the pipette it is only necessary to fill it to the degree on the stem corresponding to the degree brix found in the preliminary trial.
The quantities of juice corresponding to each degree and fractional degree of the brix spindle are given in the following table; calculated for the normal weight 26.048 grams for the ventzke and for 16.19 grams for the laurent scale. The measured quantities of juice are placed in a 100 cubic centimeter sugar flask, treated with the proper quantity of lead subacetate, the volume completed to the mark, and the juice filtered and polarized in a 200 millimeter tube. The reading of the polariscope is divided by two for the factor 26.048 and by three for the factor 16.19.
Table for Use of Sucrose Pipettes.
| Degrees brix. | Cubic centimeters of juice for 26.048 factor. Divide reading by two. | Degrees brix. | Cubic centimeters of juice for 16.19 factor. Divide reading by three. |
|---|---|---|---|
| 5.0 | 51.1 | 5.0 | 47.6 |
| 5.4 | 51.0 | 5.7 | 47.5 |
| 5.7 | 50.9 | 6.3 | 47.4 |
| 6.4 | 50.8 | 6.8 | 47.3 |
| 6.9 | 50.7 | 7.3 | 47.2 |
| 7.4 | 50.6 | 7.8 | 47.1 |
| 7.9 | 50.5 | 8.3 | 47.0 |
| 8.4 | 50.4 | 8.9 | 46.9 |
| 8.9 | 50.3 | 9.5 | 46.8 |
| 9.4 | 50.2 | 10.0 | 46.7 |
| 9.9 | 50.1 | 10.5 | 46.6 |
| 10.4 | 50.0 | 11.0 | 46.5 |
| 10.9 | 49.9 | 11.6 | 46.4 |
| 11.4 | 49.8 | 12.1 | 46.3 |
| 11.9 | 49.7 | 12.7 | 46.2 |
| 12.4 | 49.6 | 13.3 | 46.1 |
| 12.9 | 49.5 | 13.8 | 46.0 |
| 13.4 | 49.4 | 14.3 | 45.9 |
| 13.9 | 49.3 | 14.8 | 45.8 |
| 14.4 | 49.2 | 15.3 | 45.7 |
| 14.9 | 49.1 | 15.9 | 45.6 |
| 15.4 | 49.0 | 16.4 | 45.5 |
| 15.9 | 48.9 | 17.0 | 45.4 |
| 16.4 | 48.8 | 17.5 | 45.3 |
| 16.9 | 48.7 | 18.0 | 45.2 |
| 17.4 | 48.6 | 18.6 | 45.1 |
| 17.9 | 48.5 | 19.1 | 45.0 |
| 18.4 | 48.4 | 19.7 | 44.9 |
| 18.9 | 48.3 | 20.2 | 44.8 |
| 19.4 | 48.2 | ||
| 19.9 | 48.1 |
In ordering sucrose pipettes the factor for which they are to be graduated should be stated.
It is evident also that with the help of the foregoing table the measurements may be made by means of a burette. For instance, if the degree brix is found to be 19.9, 48.1 cubic centimeters are to be used. This quantity can be easily run from a burette. In order to make the pipette more convenient it has been customary in this laboratory, as practiced by Carr, to attach a glass tube with a stopcock by means of a rubber tube to the upper part of the pipette, whereby the exact level of the juice in the stem of the pipette can be easily set at any required mark.
In the polarization of dilute solutions, such as are found in the saps and juices referred to above, it must not be forgotten that the gyrodynat of the sucrose is increased as the density of the solution is diminished. This change introduces a slight error into the work which is of no consequence from a technical point of view, but becomes a matter which must be considered in exact determinations. To avoid the annoyance of calculating the gyrodynat for every degree of concentration, tables have been constructed by Schmitz and Crampton by means of which the actual percentage of sugar, corresponding to any degree of polarization, is determined by inspection. These tables may be used when extremely accurate work is required.[173]
Figure 64. Gird’s
Gravimeter.
207. Measuring Sugar Juices with a Gravimeter.—A convenient method of weighing sugar juices is the gravimetric process designed by Gird.[174] The apparatus is fully illustrated by [Fig. 64]. The hydrometer F has a weight of 26.048 grams and its stem is also graduated in degrees brix. The juice is poured into the cylinder A and allowed to stand until air bubbles have escaped. In filling A the finger is held over the orifice G so that the siphon tube B is completely filled, the air escaping at the vent C. After the tube is filled the finger is withdrawn from G and all the liquid which will run out at G allowed to escape. The sugar flask D is now brought under G and the hydrometer F allowed to descend into A. The hydrometer will displace exactly its own weight of liquid. For convenience of reading, the index E may be used which is set five degrees above the surface of the liquid in A. The number of degrees brix read by E is then diminished by five. The hydrometer has been improved since the description given by the addition of a thermometer which, in addition to carrying a graduation in degrees, also shows the correction to be made upon the degree brix for each degree read. It is evident that the hydrometer may be made of any weight, and thus the delivery of any desired amount of juice be secured.
208. Determination of Reducing Bodies in Cane Juices.—Sucrose in cane juices is constantly accompanied with reducing sugars, or other bodies which have a similar action on fehling liquor, which interfere to a considerable degree with the practical manufacture of sugar. It is important to determine with a moderate degree of accuracy the quantity of these bodies. These sugars or reducing bodies are of a peculiar nature. The author pointed out many years ago that these reducing bodies were without action on polarized light, and for this reason proposed the name anoptose as one characteristic of their nature.[175] It is also found that these bodies do not yield theoretically the quantity of alcohol which a true sugar of the hexose type would give.[176] It is entirely probable, therefore, that they are quite different in their nature from many of the commonly known sugars. On account of the difficulty of separating these bodies in a pure state their actual copper reducing power is not known. For practical purposes, however, it is assumed to be the same as that of dextrose or invert sugar and the percentage of these bodies present is calculated on that assumption. In the determination of these sugars or reducing bodies, the quantity weighed may be determined by an apparatus entirely similar to the sucrose pipette just described above. The quantity of juice used should be diluted as a rule to such a degree as not to contain more than one per cent of the reducing bodies. For the best work, the juices should be clarified with lead subacetate and the excess of lead removed with sodium carbonate. For technical control work in sugar factories, this process may be omitted as in such cases rapidity of work is a matter of considerable importance and the approximate estimation of the total quantity of reducing bodies is all that is desired.
For volumetric work, the solution of copper and the method of manipulation described in paragraph [117] are most conveniently used.
209. Preservation of Sugar Juices for Analysis.—Lead subacetate not only clarifies the juices of canes and thus permits of their more exact analytical examination, but also exercises preservative effects which enable it to be used as a preserving agent and thus greatly diminish the amount of work necessary in the technical control of a sugar factory. Instead, therefore, of the analyst being compelled to make an examination of every sample of the juice, aliquot portions representing the different quantities can be preserved and one analysis made for all. This method has been thoroughly investigated by Edson, who also finds that the errors, which may be introduced by the use of the lead subacetate in the analytical work, may be entirely avoided by using the normal lead acetate.[177]
In the use of the normal lead acetate, much less acetic acid is required in the polariscopic work than when the subacetate is used. The normal lead acetate is not so good a clarifying agent as the subacetate, but its efficiency in this respect is increased by the addition of a little acetic acid. In its use, it is not necessary to remove the lead, even for the determination of the reducing bodies.
For further details in regard to the technical determination of reducing bodies, special works may be consulted.[178]
210. Direct Determination of Sugars in Canes.—The methods, which have just been described, of securing the juices of cane by pressure and of determining the sugars therein, do not give the actual percentage of sugar in the cane. An approximate result may be secured by assuming that the cane is composed of ninety parts of juice and ten parts of cellular tissues and other insoluble matters. This assumption is approximately true in most cases, but there are often conditions arising which render the data calculated on the above assumption misleading. In any particular case in order to be certain that the correct percentage of sugar is secured it will be necessary to determine the fiber in the cane. This is an analytical process of considerable labor and especially so on account of the difficulty of securing samples which represent the average composition of the cane. The fibrous structure of the canes, the hardness of their external covering and the toughness of their nodes or joints render the sampling extremely difficult. Moreover, the content of sugar varies in different parts of the cane. The parts nearest the ground are, as a rule, richer than the upper joints and this is especially true of sugar cane. In order, therefore, to get a fair sample, even of a single cane, all parts of it must be considered. Several methods of the direct determination of sugar in canes have been proposed and will be described below.
Figure 65. Machine for Cutting Canes.
211. Methods of Cutting or Shredding the Cane for Analytical Purposes.—A simple method of cutting canes into small pieces which will permit of an even sampling is very much to be desired. The cutting apparatus shown in [Fig. 65] has been long in use in this laboratory. The canes by it are cut into thin slices, but the cutting edge of the knife being perpendicular to the length of the cane renders the use of the instrument somewhat laborious and unsatisfactory. A considerable time is required to cut a single cane and the slices which are formed should be received in a vessel which will protect them as much as possible from evaporation during the process of the work. Instead of the apparatus above a small cane cutting machine arranged with four knives on a revolving disk maybe used. The apparatus is shown in [Fig. 66]. The cane is fed against the knives through the hole shown in the open front of the apparatus and the knives thus strike the cane obliquely.[179] The knives can be set in the revolving disk at any desired position so as to cut the canes into chips as fine as may be desired. The cossettes furnished by this method may be sampled directly for the extraction of the sugar. In the case of the cossettes from both instruments described above a finer subdivision may be secured by passing them through a sausage cutter.
Figure 66. Cane Cutting Mill.
The best method for shredding canes, however, is to pass them through the apparatus described on [page 9]. That machine gives an extremely fine, moist mass, which is of uniform nature and capable of being directly sampled.
212. Methods of Determination.—Even the finely divided material obtained by the machine just described is not suited to give an instantaneous diffusion for polarization as is done by the finely ground beet pulp to be described further on. For the determination of sugar a proper weight of the cossettes or pulp obtained as described above, taken after thorough mixing, is placed in a flask graduated properly and treated with water.[180]
The flask in which the mixture takes place should be marked to compensate for the volume of the fiber of the cane. When the normal weight of cane is taken for the ventzke scale, viz., 26.048, the flask should be graduated at 102.6 cubic centimeters. If double the normal weight be taken, the flask should be graduated at 205.2 cubic centimeters. This graduation is based on the assumption of the presence of fiber amounting to ten per cent of the weight of the cossettes. The fiber is so nearly the density of the juice obtained as to be regarded as one gram equal to one cubic centimeter. The flask is at first filled almost full of water and then warmed to near the boiling point for an hour with frequent shaking. It is then filled to a little above the mark, the contents well mixed and warmed for ten minutes more with frequent shaking. After cooling, the volume is made up to the mark, well shaken and poured upon a filter. The filtrate is collected in a sugar flask marked at fifty and fifty-five cubic centimeters. When filled to the first mark a proper quantity of lead subacetate is added, the volume completed to the second mark with water, the contents of the flask well shaken, poured upon a filter and the filtrate polarized in the usual way.
The reducing sugar is determined in an aliquot part of the filtrate by one of the alkaline copper methods.
213. Determination by Drying and Extraction.—Instead of the diffusion and polarization method just described, the fine pulp obtained may be dried, the dried residue ground in a drug mill and extracted with aqueous alcohol or with water.
To facilitate the calculation when this method is employed, the water content of a small portion of the well sampled pulp is determined. The rest of the pulp is dried, first for a few hours at a temperature not above 60° or 70°, and then at the temperature of boiling water, either in the open air or a partial vacuum, until all the water is driven off. The dried residue can then be preserved in well stoppered bottles for the determination of sugar at any convenient period. The finely ground dried residue for this purpose is placed in an extraction apparatus and thoroughly exhausted with eighty per cent alcohol. The extract is dried and weighed, giving the total weight of all sugars present. After weighing, the extract is dissolved in water, made up to a definite volume and the reducing sugars determined in an aliquot portion thereof by the usual methods. The weight of reducing sugars found, calculated for the whole extract deducted from the total weight of this extract will give the weight of the sucrose in the sample. From this number the content of sugar in the original cane is determined from the percentage of water found in the original sample.
Example.—In a sample of finely pulped canes the content of water is found to be 76.5 per cent. The thoroughly dried pulp is ground and extracted with aqueous alcohol. Five grams give two and five-tenths grams of the extract. The extract is dissolved in water, made up to a definite volume and the reducing sugars determined in an aliquot part and calculated for the whole, amounting to 150 milligrams. The extract is therefore composed of 2.35 grams of sucrose and 0.15 gram of reducing sugars. The calculation is now made to the original sample which contained 76.5 per cent of water and 23.5 per cent of dry matter, as follows:
5 : x :: 23.5 : 100, whence x = 21.27,
the weight of the original material corresponding to five grams of the dry substance. The original composition of the sample is therefore expressed by the following numbers:
| Per cent. | |
| Sucrose | 11.1 |
| Reducing sugars | 0.7 |
| Water | 76.5 |
| Fiber (insoluble matter) | 11.7 |
214. Examination of the Bagasse.—The method just described for the examination of canes may be also applied to the analysis of bagasses, with the changes made necessary by the increased percentage of fiber therein. On account of the large surface exposed by the bagasse, the sampling, shredding and weighing should be accomplished as speedily as possible to avoid loss of moisture.
The optical examination of bagasses is rendered difficult by reason of the uneven pressure to which the canes are subjected. With fairly good milling in technical work the bagasses will have at least thirty per cent of fiber. The method for the polariscopic examination is therefore based upon that assumption, but the volume of the solution must be changed for varying percentages of fiber in the bagasse. On account of the smaller percentage of sugar, it is convenient to take double or three times the normal weight of the bagasse for examination. Since large sugar flasks are not commonly to be had the diffusion of the bagasse may be conducted in a quarter liter flask. In a quarter liter flask place 52.096 grams of the finely shredded bagasse, very nearly fill the flask with water and extract the sugar as described for canes in the foregoing paragraphs. In the weight of bagasse used there will be, in round numbers, fifteen grams of fiber. When the volume of water is completed to the mark the actual content of liquid in the flask will therefore be only 235 cubic centimeters. Fifty cubic centimeters of the filtrate are placed in a sugar flask marked at fifty and fifty-five cubic centimeters, the proper quantity of lead subacetate solution added, the volume completed to the upper mark, the contents of the flask well shaken, filtered and polarized in a 200 millimeter tube. Let the reading obtained be four degrees and increase this by one-tenth for the increased volume of solution above fifty cubic centimeters. The true reading is therefore four degrees and four-tenths. This reading, however, must be corrected, because the original volume instead of being 200 cubic centimeters, is 235 cubic centimeters. The actual percentage of sugar in the sample examined is obtained by the following proportion:
200 : 235 = 4.4 : x.
The correct reading is therefore 5°.2, the percentage of sugar in the sample examined.
The results obtained by the method just described may vary somewhat from the true percentage by reason of the variation of the content of fiber in the bagasse. It is, however, sufficiently accurate for technical control in sugar factories and on account of its rapidity of execution is to be preferred for this purpose. More accurate results would be obtained by drying the bagasse, and proceeding with the examination in a manner entirely analogous to that described for the extraction of sugar from dried canes by aqueous alcohol. In both instances the reducing sugar is determined in the manner already mentioned.
215. Determination of Fiber in Cane.—In estimating the content of sugar in canes by the analysis of the expressed juices, it is important to make frequent determinations of the fiber for the purpose of obtaining correct data for calculation. In periods of excessive drought, or when the canes are quite mature, the relative content of fiber is increased, while, on the other hand, in case of immature canes, or during excessive rainfalls, it is diminished. The chief difficulty in determining the content of fiber in canes is found in securing a representative sample. On account of the hard and fibrous nature of the envelope and of their nodular tissues, canes are reduced to a fine pulp with great difficulty by the apparatus in ordinary use. A fairly homogeneous pulp, however, may be obtained by means of the shredder described on [page 9]. The canes having been shredded as finely as possible, a weighed quantity is placed in any convenient extraction apparatus and thoroughly exhausted with hot water. The treatment with hot water should be continued until a few drops of the extract evaporated on a watch glass will leave no sensible residue. The residual fiber is dried to constant weight at the temperature of boiling water, cooled in a desiccator and rapidly weighed and the percentage of fiber calculated from the data obtained. On account of the great difficulty of securing a homogeneous pulp, even with the best shredding machines, the determination should be made in duplicate or triplicate and the mean of the results entered as the percentage of fiber. The term fiber as used in this sense, must not be confounded with the same term employed in the analysis of fodders and feeding stuffs. In the latter case the term is applied to the residue left after the successive treatment of the material with boiling, dilute acid and alkali. The analysis of canes for feeding purposes is conducted in the general manner hereinafter described for fodders.
216. Estimation of Sugar in Sugar Beets.—The methods employed for the determination of the sugar content of beets are analogous to those used for canes, with such variations in the method of extraction as are made possible and necessary by the difference in the nature of these sacchariferous plants. The sugar beet is more free of fiber and the hard and knotty substances composing the joints of plants are entirely absent from their composition. For this reason they are readily reduced to a fine pulp, from which the sugar is easily extracted. The analytical processes are also greatly simplified by the complete absence of reducing sugars from the juices of healthy beets. The only sugar aside from sucrose which is present in these juices is raffinose, and this is not found in healthy beets, except when they have been injured by frost or long keeping. In practical work, therefore, the determination of sucrose completes the analysis in so far as sugars are concerned. Four methods of procedure will illustrate all the principles of the various processes employed.
217. Estimation of Sucrose in the Expressed Juice.—In the first method the beets are reduced by any good shredding machine, to a fine pulp, which is placed in a press and the juice expressed. In this liquor, after clarification with lead subacetate, the sucrose is determined by the polariscope. The methods of measuring, clarifying and polarizing are the same as those described for saccharine juices in paragraphs [83-85]. The mean percentage of juice in the sugar beet is ninety-five. The corrected polariscopic reading obtained multiplied by 0.95 will give the percentage of sugar in the beet.
Example.—The solids in a sample of beet juice, as measured by a brix spindle, are 17.5 per cent. Double the normal weight of the juice is measured from a sucrose pipette, placed in a sugar flask, clarified, the volume completed to 100 cubic centimeters, the contents of the flask well shaken and filtered. The polariscopic reading obtained is 29°.0. Then (29.0 ÷ 2) × 0.95 = 13.8 = percentage of sucrose in the beet.
218. Instantaneous Diffusion.—In the second process employed for determining the sugar content of beets, the principle involved depends on the use of a pulp so finely divided as to permit of the almost instant diffusion of the sugar present throughout the added liquid. This diffusion takes place even in the cold and the process thus presents a convenient and rapid method for the accurate determination of the percentage of sugar in beets. The pulping is accomplished by means of the machine described on [page 10], or the one shown in [Fig. 67]. The beet is pressed against the rapidly revolving rasp by means of the grooved movable block and the finely divided pulp is received in the box below. These machines afford a pulp which is impalpable and which readily permits an almost instantaneous diffusion of its sugar content.
Fig 67. Apparatus for Pulping Beets.
219. Pellet’s Method of Cold Diffusion.—The impalpable pulp having been obtained, by one of the processes described, the content of sugar therein is determined as follows:[181]
A normal or double normal quantity of the pulp is quickly weighed, to avoid evaporation, in a sugar dish with an appropriate lip, and washed into the flask, which should be graduated, as shown in [Fig. 68], to allow for the volume of the fiber or marc of the beet. Since the beet pulp contains, on an average, four per cent of marc, the volume which is occupied thereby is assumed to be a little more than one cubic centimeter. Since it is advisable to have as large a volume of water as convenient, it is the practice of Pellet to wash the pulp into a flask graduated at 201.35 cubic centimeters. If a 200 cubic centimeter flask be used, the weight of the pulp should be 25.87 instead of 26.048 grams. After the pulp is washed into the flask, about six cubic centimeters of lead subacetate of 30° baumé are added, together with a little ether, to remove the foam. The flask is now gently shaken and water added to the mark and the contents thoroughly shaken. If the pulp is practically perfect, the filtration and polarization may follow immediately. The filter into which the contents of the flask are poured should be large enough to hold the whole quantity. It is recommended to add a drop or two of strong acetic acid just before completing the volume of the liquid in the flask to the mark. The polarization should be made in a 400 millimeter tube, which will give directly the percentage of sugar present. It is not necessary to heat the solution in order to insure complete diffusion, but the temperature at which the operation is conducted should be the ordinary one of the laboratory. In case the pulp is not as fine as should be, the flask should be allowed to stand for half an hour after filling, before filtration. An insufficient amount of lead subacetate may permit some rotatory bodies other than sugar to pass into solution, and care should be taken to have always the proper quantity of clarifying material added. The presence of these rotating bodies, mostly of a pectic nature, may be shown by extracting the pulp first with cold water until all the sugar is removed, and afterwards with boiling water. The liquor obtained from the last precipitation will show a decided right-handed rotation, unless first treated with lead subacetate, in which case the polarization will be zero. A very extended experience with the instantaneous cold aqueous diffusion has shown that the results obtained thereby are quite as reliable as those given by hot alcoholic or aqueous digestion.
220. Flask for Cold Diffusion and Alcohol Digestion.—For convenience in washing the pulp into the sugar flask, the latter is made with an enlarged mouth as shown in [Fig. 68]. The dish holding the weighed quantity of pulp is held with the lip in the mouth of the flask, and the pulp washed in by means of a jet of water furnished from a pressure bottle or washing flask. The flask shown is graduated for the normal weight of pulp, viz., 26.048 grams. The marking is on the constricted neck and extends from 100 to 101.3 cubic centimeters. This permits of making the proper allowance for the volume occupied by the marc or fiber, but this is unnecessary for the usual character of control analyses. In the case of healthy, fresh beets, the volume occupied by the marc is nearly one and three-tenths cubic centimeters for the normal polariscopic weight of 26.048 grams of pulp. For the laurent instrument this volume is nearly one cubic centimeter.
Figure 68. Apparatus for Cold Diffusion.
221. Extraction with Alcohol.—The third method of determining sugar in beets is by alcoholic extraction. The principle of the method is based on the fact that aqueous alcohol of not more than eighty per cent strength will extract all the sugar from the pulp, but will not dissolve the pectic and other rotatory bodies, which, in solution, are capable of disturbing the rotatory power of the sugar present. It is also further to be observed that the rotatory power of pure sucrose, in an aqueous alcoholic solution, is not sensibly different from that which is observed in a purely aqueous liquid. The pulp, which is to be extracted, should be in as fine a state of subdivision as convenient, and the process may be carried on in any of the forms of extraction apparatus already described, or in the apparatus shown in [Fig. 69]. The extraction tube, of the ordinary forms of apparatus, however, is scarcely large enough to hold the required amount of pulp, and therefore special tubes and forms of apparatus have been devised for this method of procedure. In weighing the pulp for extraction, a quarter, half, or the exact amount required for the polariscope employed, should be used. If the tubes are of sufficient size the full weight may be taken, viz., 26.048 or 16.19 grams for the instruments in ordinary use. Since the pulp contains a large quantity of water, the extraction could be commenced with alcohol of standard strength, viz., about ninety-five per cent. The volume of alcohol employed should be such as will secure a strength of from seventy to eighty per cent when mixed with the water contained in the pulp. The flask receiving the extract should be kept in continuous ebullition and the process may be regarded as complete in about one hour, when the pulp has been properly prepared. The method of extracting beet pulp with alcohol is due to Scheibler, and in its present form the process is conducted according to the methods described by Scheibler, Sickel, and Soxhlet.[182]
Fig. 69. Sickel-Soxhlet Extractor.
If the pulp be obtained by any other means than that of a fine rasp, the extraction of the sugar by the aqueous alcohol takes a long time, and even a second extraction may be necessary. It is convenient to use as a flask for holding the solvent, one already graduated at 100 or 110 cubic centimeters. A flask especially constructed for this purpose, has a constricted neck on which the graduations are made, and a wide mouth serving to attach it to the extracting apparatus, as shown in [Fig. 68]. When the extract is obtained in this way, it is not necessary to transfer it to a new flask before preparing it for polarization. When the extraction is complete, the source of heat is removed, and when all the alcohol is collected in the flask, the latter is removed from the extraction apparatus, cooled to room temperature, a sufficient quantity of lead subacetate added, the flask well shaken, the volume completed to the mark with water, again well shaken and the contents of the flask thrown upon the filter. It is important to avoid loss of alcohol during filtration. For this purpose it is best to have a folded filter and to cover the funnel immediately after pouring the contents of the flask upon the filter paper, with a second larger funnel. The stem of the funnel carrying the filter paper, should dip well into the flask receiving the filtrate. As in other cases of filtering sugar juices for polarization, the first portions of the filtrate received should be rejected. The percentage of sugar is obtained in the filtrate in the usual way.
Where a weight of pulp equal to the normal factor of the polariscope employed is used, and the extract collected in a 100 cubic centimeter flask, the percentage of sugar is directly obtained by making the reading in a 200 millimeter tube. With other weights of pulp, or other sizes of flask, the length of the observation tube may be changed or the reading obtained corrected by multiplication or division by an appropriate factor. A battery of sickel-soxhlet extractors is shown in [Fig. 69].[183]
Fig. 70.
222. Scheibler’s Extraction Tube.—In order to secure a speedy extraction of large quantities of pulp, Scheibler recommends the use of the extraction tube shown in [Fig. 70].[184] The apparatus is composed of three concentric glass cylinders. The outer and middle cylinders are sealed together at the top, and the inner one is movable and carries a perforated diaphragm below, for filtering purposes. Near the top it is provided with small circular openings, whereby the alcoholic vapors may gain access to the condenser (not shown). The middle cylinder is provided with two series of apertures, through the higher of which the vapor of alcohol passes to the condenser, while the alcohol which has passed through the pulp and collected between the inner and middle cylinders, flows back through the lower into the flask (not shown) containing the boiling alcohol.
The middle cylinder is provided with a curved bottom to prevent the filtering end of the inner tube from resting too tightly against it.
The tube containing the pulp is thus protected from the direct heat of the alcoholic vapors during the progress of extraction by a thin cushion of liquid alcohol.
223. Alcoholic Digestion.—The fourth method of determining sugar in beet pulp, is by means of digestion with hot alcohol. The principle of this method is precisely the same as that which is involved in aqueous diffusion in the cold. The diffusion, however, in the case of the alcohol, is not instantaneous, but is secured by maintaining the mixture of the pulp and alcohol for some time at or near the boiling point. The methods of preparing the pulp, weighing it and introducing it into the digestion flask are precisely those used for aqueous digestion, but in the present case a somewhat coarser pulp may be employed. The method is commonly known as the rapp-degener process.[185]
Any convenient method of heating the alcohol may be used. In this laboratory the flasks are held on a false bottom in a bath composed of two parts of glycerol and one of water. One side of the bath holder is made of glass, as shown in [Fig. 71], in order to keep the flasks in view. In order to avoid the loss of alcohol, the digestion flask should be provided with a reflux condenser, or be attached to an ordinary condenser, which will reduce the vapors of alcohol again to a liquid. Unless the weather be very warm, the reflux condenser may consist of a glass tube of rather wide bore and at least one meter in length, as shown in [Fig. 71]. A slight loss of alcohol during the digestion is of little consequence. A convenient method of procedure is the following.
Double the quantity of the beet pulp required for the ventzke polariscope, viz., 52.096 grams, weighed in a lipped metal dish, is washed, by means of alcohol, into a flask marked at 202.6 cubic centimeters, and the flask filled two-thirds with ninety-five per cent alcohol and well shaken. Afterwards, a proper quantity of lead subacetate is added, and then sufficient alcohol to complete the volume to the mark. The flask is then attached to the condenser, placed in a water-glycerol bath and heated to a temperature of 75° for about forty-five minutes. At the end of this time, the flask is removed from the bath and condenser, cooled quickly with water, alcohol added to the mark and well shaken. The filtration should be accomplished with precautions, to avoid the loss of alcohol mentioned in paragraph [221]. The filtrate is examined in the polariscope in a 200 millimeter tube, and the reading obtained gives directly the percentage of sugar in the sample examined. Half the quantity of pulp mentioned, in a 101.3 cubic centimeter flask, may also be used. A convenient form of arranging a battery of flasks is shown in the accompanying figure.
Fig. 71. Battery for Alcoholic Digestion.
224. Determination of Sugar in Mother Beets.—In selecting mother beets for seed production, it is necessary to secure only those of a high sugar content. This is accomplished by boring a hole about two and a half centimeters in diameter obliquely through the beet by means of the apparatus shown in [Fig. 72].
The beet is not injured for seed production by this process, and the pulp obtained is used for the determination of sugar. The juice is expressed by means of the small hand press shown in [Fig. 73]. Since only a small quantity of juice is obtained, it is advisable to prepare it for polarization in a sugar flask marked at fifty cubic centimeters. The density of the juice, by reason of its small volume, is easiest obtained by the hydrostatic balance, as described in paragraph [53]. In lieu of this, the juice may be quickly weighed in a counterbalanced dish on a balance giving results accurate to within one milligram. The rest of the analytical process is similar to that already described.
Fig. 72. Rasp for Sampling Mother Beets.
Fig. 73. Hand Press for Beet Analysis.
Fig. 74.
225. Aqueous Diffusion.—The process of instantaneous aqueous diffusion may also be applied to the examination of mother beets. For this purpose the beets are perforated by a rasp, devised by Keil, shown lying on the floor in [Fig. 72], the characteristics of which are shown in [Fig. 74]. The conical end of the rasp is roughened in such a way as to reduce the beet to an impalpable pulp. This end is fastened by a bayonet fastening to the cylindrical carrier or arm in such a way that, by means of a groove in the conical end of the rasp, the pulp is introduced into the cylinder. The cylinder is provided with a small piston by means of which the pulp can be withdrawn when the cylindrical portion of the rasp is detached from the driving machinery. It is important that the rasp be driven at a high rate of speed, viz., from 1500 to 2000 revolutions a minute. The sample of pulp at this rate of revolution is taken almost instantly, and with skilled manipulators the whole operation of taking a sample, removing the rasp by means of its bayonet fastenings, withdrawing the sample of pulp and replacing the rasp ready for another operation does not consume more than from ten to twenty seconds. From three to four samples may thus be taken in a minute. The samples of pulp as taken are dropped into numbered dishes corresponding to the numbers on the beets. One-quarter of the normal weight for the polariscope is used for the analysis. The pulp is placed in a fifty cubic centimeter flask, water and lead subacetate added, the flask well shaken, filled to the mark with water, again well shaken, the contents thrown on the filter, and the filtrate polarized in a 400 millimeter tube, giving the direct percentage of sugar. For practical purposes the percentage of marc in the beet may be neglected. If the polarization take place in a 200 millimeter tube the number obtained should be multiplied by two for the content of sugar.
In numbering sugar beets which are to be analyzed for seed production, it is found that a small perforated tin tag bearing a number may be safely affixed to the beet by means of a tack. It is not safe to use paper tags as they may become illegible by becoming wet before the sorting of the beets is completed. Where from 1000 to 2000 beets are to be examined in a day, the number of the beets and the dishes corresponding thereto must be carefully controlled to avoid confusion and mistakes.
226. Determination of Sugars without Weighing.—An ingenious device for the rapid analysis of mother beets is based upon the use of a machine which cuts from the beet a core of given dimensions and this core is subsequently reduced to a pulp which is treated with cold water and polarized in the manner described above. The cutting knives of the sampler can be adjusted to take a core of any desired size. Since the beets used for analysis have essentially the same specific gravity, the cores thus taken weigh sensibly the same and the whole core is used for the analysis, thus doing away with the necessity of weighing. The core obtained is reduced to a pulp in a small machine so adjusted as to permit the whole of the pulp, when prepared, to be washed directly into the sugar flask. By the use of this machine a very large number of analyses can be made in a single day, and this is highly important in the selection of mother beets, for often 50,000 or 100,000 analyses are to be made in a short time.
Fig. 75. Tube for Continuous Observation.
227. Continuous Diffusion Tube.—To avoid the delay occasioned by filling and emptying observation tubes in polariscopic work, where large numbers of analyses of canes and beets are to be made, Pellet has devised a continuous diffusion tube, by means of which a solution, which has just been observed, is rapidly and completely displaced by a fresh solution. This tube, improved by Spencer, is shown in [Fig. 75]. The fresh solution is poured in at the funnel, displacing completely the old solution which flows out through the tube at the other end. The observer watches the field vision and is able to tell when the old solution is completely displaced by the clearing of the field, at which time the reading of the new solution can be quickly made. When solutions are all ready for examination an expert observer can easily read, by the aid of this device, from four to five of them in a minute.
228. Analysis of Sirups and Massecuites.—The general principles which control the analysis of sirups and massecuites are the same whether these products be derived from canes or beets. In the case of the products of canes, the sirups or massecuites contain chiefly sucrose, invert sugar, and other copper reducing bodies, inorganic matters and water. In the case of products derived from sugar beets the contents are chiefly sucrose, inorganic matters, a trace of invert sugar, raffinose and water. The principles of the determination of these various constituents have already been described.
229. Specific Gravity.—The specific gravity of sirups and molasses can be determined by the spindle in the usual way, but in the case of molasses which is quite dense, the spindle method is not reliable. It is better, therefore, both in molasses and massecuites, to determine the density by dilution. For this purpose, as described by Spencer, a definite weight of material, from 200 to 250 grams, is dissolved in water and the volume of the solution completed to half a liter. A portion of the solution is then placed in a cylinder and the quantity of total solids contained therein determined in the usual way by a brix or specific gravity hydrometer. In case 250 grams of the material be used the calculation of the brix degree for the original material is conducted according to the following formula:
| x = | G × B × V |
| W |
In the above formula x is the required brix degree, V the volume of the solution, B the observed brix degree of the solution, and G the corresponding specific gravity obtained from the table on [page 73]. When only small quantities of the material are at hand the hydrostatic balance ([53]) should be employed. For this purpose twenty-five grams of the material are dissolved in water and the volume of the solution made up to 100 cubic centimeters. The sinker of the hydrostatic balance is placed in the solution and equilibrium secured by placing the weights upon the arm of the balance in the usual manner. Since the arm of the balance is graduated to give, by direct reading, the specific gravity, the density can be obtained at once.
Example.—Let the position of the weights or riders upon the balance arm be as follows:
| (1) at point of suspension of the bob | = 1.000 |
| (3) at mark 7 on beam | = 0.07 |
| (4) at mark 9 on beam | = 0.009 |
| Specific gravity | = 1.079 |
The nearest brix degree corresponding to this specific gravity ([58]) is 19. The total weight of the solution is equal to 100 × 1.079, viz., 107.9 grams. Since the solution contains nineteen per cent of solid matter as determined by the hydrostatic balance, the total weight of solid matter therein is 107.9 × 19 ÷ 100 = 20.5 grams. The total per cent. of solid matter in the original sample is therefore 20.5 ÷ 25 × 100 = 82 and the specific gravity corresponding thereto ([page 74]) is 1.42934.
The specific gravity of a massecuite may also be determined in pyknometers especially constructed for this purpose.[186]
230. Determination Of Water.—The accurate determination of water in sirups and massecuites is a matter of considerable difficulty. The principles of conducting the process ([26]), applicable also to the determination of water in honeys and other viscous liquids, are as follows: In all cases where invert sugar is present the drying should be conducted at a temperature not exceeding 75° or 80°. In dense molasses and massecuites a weighed quantity should be dissolved and made up to a definite volume and an aliquot portion taken for the determination. In order to secure complete desiccation at a low temperature, the drying should be accomplished in partial vacuum (pages [22], [23]). The process of desiccation should be conducted in shallow, flat-bottom dishes which may be conveniently and cheaply made of aluminum and the process is hastened by filling the dish previously with thoroughly dried fragments of pumice stone. When the sample does not contain any invert sugar the desiccation can be safely accomplished at the temperature of boiling water. Drying should be continued in all cases until practically constant weight is obtained.
231. Determination Of Ash.—Ash is an important constituent of the sirups, molasses, and massecuites from canes and exists in very much larger quantities in the same products from beets. The ash may be determined directly by careful incineration, but it is customary to add a few drops of sulfuric acid, sufficient to combine with all the bases present and be in slight excess. The presence of sulfuric acid is of some advantage in the beginning of the carbonization and renders the process somewhat easier of accomplishment. When sulfuric acid is used, the weight of ash obtained must be diminished by one-tenth to allow for the increased weight obtained by the conversion of the carbonates into sulfates. In general, the principles and methods described on [pages 36-40] are to be employed.
232. Determination of Reducing Sugars in Sirups, Molasses, and Massecuites.—The quantity of reducing sugars in the products derived from the sugar beet, as a rule, is insignificant. In the products from sugar cane there are large quantities of reducing matters which, in general, are determined by any of the standard methods already given. It has been shown by the author[187] that the juices of healthy sugar canes contain a small quantity of invert sugar, but this statement has been contradicted by Bloufret.[188] It is certain, however, that the reducing bodies derived from the products of manufacture of sugar cane and sorghum deport themselves in a manner somewhat different from pure invert sugar. In the absence of definite information in respect of the constitution of these bodies, the methods applicable to dextrose and invert sugar may be applied.
Since the paragraphs relating to these processes were printed some important improvements in the preparation of the alkaline copper solutions have been made. The copper carbonate solution, as has already been said, is peculiarly suited to the determination of reducing sugars in the presence of sucrose and the modified forms of this solution, and the methods of employing them with invert sugar, dextrose, levulose, and maltose, are described below.
233. Estimation of Minute Quantities of Invert Sugar in Mixtures.—The method of Hiller and Meissl, paragraph [142], may be used for the estimation of small quantities of invert sugar in mixtures. A modified form of Soldaini’s reagent is, however, to be preferred for this purpose. Ost has proposed and tested a copper carbonate solution for the purpose mentioned which gives reliable results.[189] The solution has the following composition:
| One liter contains | 3.6 | grams | crystallized copper sulfate. |
| 250.0 | ” | potassium carbonate. | |
| 100.0 | ” | hydrogen potassium sulfate. |
This reagent undergoes no change when kept for a long while, especially in large vessels. Even in smaller vessels it can be kept for a year or more without undergoing any change.
The method of analysis is the same as that described in paragraph [128], with the exception that the boiling is continued for only five minutes instead of ten, and the quantities of the copper and sugar solutions used are doubled, being 100 and fifty cubic centimeters respectively. In no case must the solution used contain more than thirty-eight milligrams of invert sugar. The quantity of sucrose in the mixture is obtained by polarization ([94]). Ost has also recalculated the reduction values of the common sugars for the strong copper carbonate solution, and the numbers obtained are slightly different from those given on [page 142].[190]
For different percentages of invert sugar in mixtures of sucrose, the quantities of invert sugar are calculated from the number of milligrams of copper obtained by the following table:
- (A) = Milligrams of copper obtained.
- (B) = Pure invert sugar.
- (C) = Invert sugar.
- (D) = Sucrose.
| Milligrams of Invert Sugar in Mixtures of | ||||||||
|---|---|---|---|---|---|---|---|---|
| 5(C) | 2(C) | 1.5(C) | 1.0(C) | 0.8(C) | 0.6(C) | 0.5(C) | ||
| (A) | (B) | 95(D) | 98(D) | 98.5(D) | 99.0(D) | 99.2(D) | 99.4(D) | 99.5(D) |
| 88 | 37.9 | 37.1 | 36.0 | 35.4 | 34.7 | 34.2 | 33.9 | 33.6 |
| 85 | 36.3 | 35.5 | 34.5 | 34.0 | 33.4 | 32.9 | 32.5 | 32.2 |
| 80 | 33.9 | 33.0 | 33.2 | 31.7 | 31.2 | 30.7 | 30.2 | 29.9 |
| 75 | 31.6 | 30.7 | 30.0 | 29.5 | 29.0 | 28.5 | 28.1 | 27.7 |
| 70 | 29.4 | 28.5 | 27.8 | 27.4 | 26.8 | 26.4 | 25.9 | 25.6 |
| 65 | 27.3 | 26.3 | 25.7 | 25.3 | 24.7 | 24.3 | 23.8 | 23.5 |
| 60 | 25.2 | 24.2 | 23.6 | 23.2 | 22.6 | 22.2 | 21.8 | 21.5 |
| 55 | 23.1 | 22.1 | 21.6 | 21.2 | 20.6 | 20.2 | 19.8 | 19.6 |
| 50 | 21.2 | 20.1 | 19.6 | 19.2 | 18.6 | 18.3 | 17.9 | 17.7 |
| 45 | 19.3 | 18.2 | 17.6 | 17.2 | 16.7 | 16.3 | 16.0 | 15.8 |
| 40 | 17.3 | 16.3 | 15.7 | 15.3 | 14.8 | 14.5 | 14.2 | 14.0 |
| 35 | 15.4 | 14.5 | 13.8 | 13.4 | 13.0 | 12.7 | 12.5 | 12.3 |
| 30 | 13.5 | 12.6 | 12.0 | 11.6 | 11.2 | 11.0 | 10.8 | 10.6 |
| 25 | 11.5 | 10.8 | 10.3 | 10.0 | 9.5 | 9.3 | 9.1 | 9.0 |
| 20 | 9.6 | 9.1 | 8.6 | 8.3 | 7.9 | 7.7 | 7.5 | 7.3 |
| 15 | 7.7 | 7.3 | 6.9 | 6.7 | 6.3 | 6.1 | 5.8 | 5.6 |
| 10 | 5.8 | 5.4 | 5.1 | 5.0 | 4.7 | 4.5 | 4.2 | 3.9 |
| Milligrams of Invert Sugar in Mixtures of | ||||||
|---|---|---|---|---|---|---|
| 0.4(C) | 0.3(C) | 0.2(C) | 0.1(C) | 0.05(C) | 0.02(C) | |
| (A) | 99.6(D) | 99.7(D) | 99.8(D) | 99.9(D) | 99.95(D) | 99.98(D) |
| 88 | 33.3 | |||||
| 85 | 32.0 | 31.8 | ||||
| 80 | 29.7 | 29.5 | ||||
| 75 | 27.4 | 27.2 | ||||
| 70 | 25.3 | 25.0 | ||||
| 65 | 23.2 | 22.8 | ||||
| 60 | 21.2 | 20.8 | 20.4 | |||
| 55 | 19.3 | 18.9 | 18.5 | |||
| 50 | 17.4 | 17.0 | 16.7 | |||
| 45 | 15.6 | 15.3 | 14.9 | |||
| 40 | 13.8 | 13.5 | 13.2 | |||
| 35 | 12.1 | 11.9 | 11.5 | 10.3 | ||
| 30 | 10.4 | 10.2 | 9.9 | 8.8 | ||
| 25 | 8.8 | 8.6 | 8.2 | 7.3 | ||
| 20 | 7.1 | 6.9 | 6.6 | 5.8 | 4.9 | |
| 15 | 5.4 | 5.2 | 5.0 | 4.4 | 3.7 | 2.0 |
| 10 | 3.8 | 3.5 | 3.4 | 3.0 | 2.5 | 1.7 |
234. Soldaini’s Method Adapted to Gravimetric Work.—By reason of their better keeping qualities and because of their less energetic action on non-reducing sugars, copper carbonate solutions are to be preferred to the alkaline copper tartrate solutions for gravimetric determinations of reducing sugars in cane juices and sugar house products, provided the difficulties which attend the manipulation can be removed. Ost has succeeded in securing perfectly satisfactory results with copper carbonate solution by slightly varying the composition thereof and continuing the boiling, for the reduction of the copper, ten minutes.[191] The copper solution is made as follows:
| 17.5 | grams | crystallized copper sulfate. |
| 250.0 | ” | potassium carbonate. |
| 100.0 | ” | ”bicarbonate. |
The above ingredients are dissolved in water and the volume of the solution completed to one liter. The object of the potassium bicarbonate is to secure in the solution an excess of carbon dioxid and thus prevent the deposition of basic copper carbonate on keeping. The manipulation is conducted as follows:
One hundred cubic centimeters of the copper solution are mixed with half that quantity of the sugar solution in a large erlenmeyer, which is placed upon a wire gauze, heated quickly to boiling and kept in ebullition just ten minutes. The sugar solution should contain not less than eighty nor more than 150 milligrams of the reducing sugar, and the quantity of the solution representing this should be diluted to fifty cubic centimeters before mixing with the copper solution. After boiling, the contents of the erlenmeyer are quickly cooled and filtered with suction through an asbestos filter and the whole of the copper suboxid washed into the filter tube. This precipitated suboxid is washed once with a little potassium carbonate solution then with hot water and finally with alcohol, well dried, heated to redness, and the copper oxid obtained reduced to metallic copper in an atmosphere of hydrogen entirely free of arsenic. From the weight of metallic copper obtained the quantity of sugar which has been oxidized is calculated from the tables below.
It is evident that the process given above may be varied so as to conform to the practice observed in this laboratory of cooling the boiling solution sufficiently at once by adding to it an equal volume of recently boiled, cold water, collecting the precipitated copper suboxid in a gooch, and, after washing it, securing solution in nitric acid and the precipitation of the copper by electrolysis.
Table Showing Milligrams Dextrose,
Levulose and Invert Sugar Oxidized,
Corresponding to Milligrams of
Copper Reduced.
Corresponding Table for Maltose.
| Milligrams copper obtained. | Milligrams maltose anhydrid oxidized. | Milligrams maltose hydrate oxidized. |
|---|---|---|
| 435 | 263.7 | 277.6 |
| 430 | 259.3 | 273.0 |
| 425 | 255.0 | 268.4 |
| 420 | 250.9 | 264.1 |
| 415 | 247.0 | 260.0 |
| 410 | 243.2 | 256.0 |
| 405 | 339.4 | 252.0 |
| 400 | 235.6 | 248.0 |
| 395 | 231.9 | 244.1 |
| 390 | 228.2 | 240.2 |
| 385 | 224.6 | 236.4 |
| 380 | 221.1 | 232.7 |
| 375 | 217.7 | 229.1 |
| 370 | 214.4 | 225.6 |
| 365 | 211.1 | 222.2 |
| 360 | 207.9 | 218.8 |
| 355 | 204.7 | 215.4 |
| 350 | 201.5 | 212.1 |
| 345 | 198.3 | 208.7 |
| 340 | 195.2 | 205.4 |
| 335 | 192.0 | 202.1 |
| 330 | 188.8 | 198.8 |
| 325 | 185.7 | 195.4 |
| 320 | 182.5 | 192.1 |
| 315 | 179.4 | 188.8 |
| 310 | 176.3 | 185.6 |
| 305 | 173.3 | 182.4 |
| 300 | 170.3 | 179.2 |
| 295 | 167.3 | 176.1 |
| 290 | 164.4 | 173.0 |
| 285 | 161.4 | 169.9 |
| 280 | 158.5 | 166.8 |
| 275 | 155.5 | 163.7 |
| 270 | 152.6 | 160.7 |
| 265 | 149.7 | 157.6 |
| 260 | 146.8 | 154.6 |
| 255 | 143.9 | 151.5 |
| 250 | 141.1 | 148.5 |
| 245 | 138.2 | 145.5 |
| 240 | 135.4 | 142.5 |
| 235 | 132.5 | 139.5 |
| 230 | 129.7 | 136.5 |
| 225 | 126.8 | 133.5 |
| 220 | 124.0 | 130.6 |
| 215 | 121.2 | 127.6 |
| 210 | 118.4 | 124.7 |
| 205 | 115.7 | 121.8 |
| 200 | 112.9 | 118.9 |
| 195 | 110.2 | 116.0 |
| 190 | 107.4 | 113.1 |
| 185 | 104.7 | 110.2 |
| 180 | 101.9 | 107.3 |
| 175 | 99.2 | 104.4 |
| 170 | 96.4 | 101.5 |
| 165 | 93.7 | 98.6 |
| 160 | 90.9 | 95.7 |
| 155 | 88.2 | 92.8 |
| 150 | 85.4 | 89.9 |
| 145 | 82.6 | 87.0 |
| 140 | 79.9 | 84.1 |
| 135 | 77.1 | 81.2 |
| 130 | 74.4 | 78.3 |
| 125 | 71.6 | 75.4 |
| 120 | 68.9 | 72.5 |
| 115 | 66.1 | 69.6 |
| 110 | 63.4 | 66.7 |
| 105 | 60.6 | 63.8 |
| 100 | 57.9 | 60.9 |
| 95 | 55.1 | 58.0 |
| 90 | 52.3 | 55.1 |
| 85 | 49.6 | 52.2 |
| 80 | 46.8 | 59.3 |
| 75 | 44.1 | 56.4 |
| 70 | 41.4 | 53.5 |
235. Weighing the Copper as Oxid.—In the usual methods of the determination of reducing bodies, the percentage is calculated either volumetrically from the quantity of the sugar solution required to decolorize a given volume of the alkaline copper solution, or the reduced copper suboxid is brought into a metallic state by heating in an atmosphere of hydrogen or by electrolytic deposition. A quicker method of procedure is found in completing the oxidation of the cupric oxid by heating to low redness in a current of air.[192] For this determination the precipitation of the cuprous oxid and its filtration are made in the usual manner. The cuprous oxid is collected in a filtering tube, made by drawing out to proper dimensions a piece of combustion tube, and has a length of about twelve centimeters in all. The unchanged part of the tube is about eight centimeters in length and twelve millimeters in diameter. It is filled by first putting in a plug of glass wool and covering this with an asbestos felt on top of which another plug of glass wool is placed. After the cuprous oxid is collected in the tube it is washed with boiling water, alcohol and ether. The rubber tube connecting it with the suction is of sufficient length to permit the tube being taken in one hand and brought into a horizontal position over a bunsen. The tube is gradually heated, rotating it meanwhile, until any residual moisture, alcohol or ether, is driven off from the filtering material. The layer of glass wool holding the cuprous oxid is gradually brought into the flame and as the oxidation begins the material will be seen to glow. The heating is continued for some time after the glowing has ceased, in all for three or four minutes, the tube and the copper oxid which it contains being brought to a low redness. The current of air passing over the red-hot material in this time oxidizes it completely. The filtering tube, before use, must be ignited and weighed in exactly the same manner as described above. The heat is so applied as not to endanger the rubber tube attached to one end of the filtering tube nor to burn the fingers of the operator as he turns the tube during the heating. After complete oxidation the tube is cooled in a desiccator and weighed, the increase of weight giving the copper oxid. For the atomic weights, 63.3 copper and 15.96 oxygen, one gram of copper oxid is equivalent to 0.79864 gram of copper, and for the weights 63.17 copper and 15.96 oxygen, one gram of copper oxid equals 0.79831 gram of copper. From the amount of metallic copper calculated by one of these factors, the reducing sugar is determined by the tables already given.
236. Estimation of Dry Substance, Polarization and Apparent Purity for Factory Control.—For technical purposes the methods of determining the above factors, proposed by Weisberg and applicable to concentrated sirups, massecuites, and molasses, may be used.[193] Five times the half normal quantity of the material, viz., 65.12 grams, are placed in a quarter liter flask, dissolved in water and the flask filled to the mark. In the well shaken mixture, which is allowed to stand long enough to be free of air, the degree brix is estimated by an accurate spindle. For example, in the case of molasses, let the number obtained be 18.8.
Fifty cubic centimeters of the solution are poured into a 100 cubic centimeter flask, the proper quantity of lead subacetate added, the flask filled to the mark with water, its contents filtered, and the filtrate polarized in a 200 millimeter tube. Let the number obtained on polarization be 22°.1. This number may be used in two ways. If it be multiplied by two the polarization of the original sample is obtained; in this case, viz., 44°.2. In the second place, if 44.2 be multiplied by 0.26048 and this product divided by the specific gravity corresponding to 18°.8. viz., 1.078, the quotient 10.68 is secured representing the polarization or per cent of sugar contained in the solution of which the degree brix was 18.8°. From the numbers 18.8 and 10.68 the apparent purity of the solution, 56.8, is calculated, viz., 10.68 × 100 ÷ by 18.8. The original product as calculated above gives a polarization of 44.2 and this number multiplied by 100 and divided by 56.8 gives 77.8, or the apparent percentage of dry matter. The original sample of molasses, therefore, had the following composition:
| Degree brix (total solids) | 77.8 | per cent. |
| Sucrose | 44.2 | ” |
| Solids, not sucrose | 33.6 | ” |
| Apparent purity | 56.8 | ” |
It is seen from the above that with a single weighing and a single polarization, and within from ten to fifteen minutes, all needful data in respect of the proper treatment of molasses for the practical control and direction of a factory can be obtained.
In case a laurent polariscope is used, five times the normal weight, viz., eighty-one grams of the raw material are used and the process conducted as above.
SUCROSE, DEXTROSE, INVERT SUGAR, LEVULOSE,
MALTOSE, RAFFINOSE, DEXTRIN AND
LACTOSE IN MIXTURES.
237. Occurrence.—Sucrose and invert sugar are found together in many commercial products, especially in raw sugars and molasses made from sugar cane, and in these products sucrose is usually predominant. They also form the principal saccharine contents of honey, the invert sugar, in this case, being the chief ingredient.
In commercial grape sugar, made from starch, dextrose is the important constituent, while in the hydrolysis of starch by a diastatic ferment, maltose is principally produced. In the manufacture of commercial glucose by the saccharification of starch with sulfuric acid, dextrin, maltose, and dextrose are the dominant products, while in the similar substance midzu ame, maltose and dextrose are chiefly found, and only a small quantity of dextrose.[194] In honeys derived from the exudations of coniferous trees are found also polarizing bodies not enumerated above and presumably of a pentose character.[195] In evaporated milks are usually found large quantities of sucrose in addition to the natural sugar therein contained. These mixtures of carbohydrates often present problems of great difficulty to the analyst, and the following paragraphs will be devoted to an elucidation of the best approved methods of solving them.