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.