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.