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 The cylinder is provided with a small piston by means of which the pulp can be withdrawn when the cylindrical portion of the rasp is detached from the driving machinery.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.