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 |