Page:The American Cyclopædia (1879) Volume XV.djvu/458

 442 SUGAR on standing it separates in impure crystals, and may be purified by redissolving in water and filtering through animal charcoal. It forms white, translucent, four-sided, trimetric prisms of great hardness. It dissolves slowly in cold water, requiring five or six times its weight. Its optical rotatory power is + 59'3. Very strong nitric acid converts milk sugar into nitro-lactine. It is brought very slowly into alcoholic fermentation by the action of yeast, but when cheese or rennet is used it is read- ily converted into lactic acid, alcohol being formed at the same time. A kind of sugar called glycyrrhizine or liquorice sugar, having the formula CaiHseOB, is found in liquorice root (glycyrrJiiza). It has a peculiar sweet taste, but cannot be made to ferment. Ac- cording to Gorup-Besanez, when boiled with dilute acids, it splits up into a resinous body called glycyrretine, OisHaaOi, and glucose. Saccharimetry. There are various methods of estimating the proportion of sugar in a given solution, which are embraced under the gene- ric term saccharimetry. They are usually em- ployed for the estimation of cane sugar. There are four principal methods : 1, by the specific gravity of the solution ; 2, by the amount of carbonic anhydride or of alcohol it will yield in fermentation ; 3, by the amount of suboxide of copper precipitable from a solution by the action of grape sugar, into which the cane sugar present is first converted ; 4, by the de- gree of rotation given to a beam of polarized light in passing through the solution. In the first and fourth methods instruments called saccharometers are employed, the term sac- charimeter being often applied to the polari- zing instrument. The specific gravity or hy- drometric saccharometer is used by brewers for determining the amount of saccharine mat- ter which has been produced in wort by the fermentation of malt. (See BREWING, and HY- DROMETEB.) The instrument is also employed by sugar makers and distillers. The brew- er's saccharometer is usually graduated so as to indicate the excess of weight of 1,000 parts of a liquid by volume over that of the same volume of distilled water. For this purpose the hydrometer is marked 1000 upon its stem at the point to which it sinks in water, and with increasing numbers below this point. If the tested solution is dense enough to float the instrument till the number 1065 is at the surface, it is said to have a specific gravity of 65 ; if only to 1020, its gravity is said to be 20. Tables are used by which the quantity of sugar may be estimated from the specific gravity thus ascertained, and the tables may be adapted to differently graduated instruments, but the one above described (Baum6's) is usually employed. As beer wort holds other substances besides sugar in solution, the method is not exact, but in experienced hands it answers all the pur- poses of the brewer. "When the solution is purely saccharine, or nearly so, as in clarified cane juice, the process is more nearly accu- rate ; but when other substances are pres- ent the precise amount of sugar may be de- termined by the second method, that of pro- ducing fermentation and estimating the quan- tity of carbonic anhydride or of alcohol which is thereby formed. The third meth- od, that by precipitation of suboxide of cop- per from an alkaline solution of tartrate of copper and potash, is briefly as follows: A standard solution, known as Fehling's, is prepared with 1 oz. of crystallized sulphate of copper, 3 oz. of bitartrate of potash, oz. of pure carbonate of potash, and 14 or 16 oz. of a solution of caustic potash of sp. gr. 1'12, with sufficient water to make the solution weigh 15,160 grs. ; 200 grs. of this so- lutioji contain an amount of copper which is completely precipitated by 1 gr. of grape sugar. In using Fehling's solution a temperature ap- proaching the boiling point should be main- tained, and the saccharine solution should be slowly added from a graduated burette. It is necessary before testing to convert the cane sugar into glucose, which is done by adding sulphuric acid and boiling. The method by polarized light is performed by employing an instrument first devised by Biot, but since modi- fied and improved by Soleil. In the article LIGHT, vol. x., pp. 449, 450, it is shown that several substances have the property of rota- ting the plane of a polarized ray, some to the right and some to the left, and also that sub- stances having the same chemical composition may rotate the ray in both directions. A so- lution of dextrose (grape sugar or glucose) has the property of right-handed rotation, while laevulose, having the same chemical composi- tion (CeHiaOa), turns the plane of polarization to the left. Quartz also, by reason of a differ- ence in its molecular structure, is in some spe- cimens right-handed and in others left-handed in its power of rotation. The original appa- ratus devised by Biot employed a tube con- taining the solution of sugar to be examined, the depth of the liquid producing a certain de- gree of rotation indicating the proportion of glucose it contained, and therefore the amount of cane sugar, this being first converted into glucose. The saccharimeter devised by M. Soleil does not measure the degree of rotation produced directly, as in Biot's instrument, but employs the principle of compensation, and furthermore employs a comparison of color, using therefore white instead of homogeneous light. The amount of compensation is mea- sured by an attachment called a compensator, which is made of two wedge-shaped pieces of quartz whose combined thickness may be varied by sliding them over each other. A copper tube, m, figs. A and B, tinned on the inside and containing the solution to be tested, is closed at both ends by two glass plates, and rests upon the support &, which also bears at its ends the tubes a and r. These tubes contain the analyzers and polarizers, which are repre- sented in section at B. Tho light of a com-