The monosalt may be easily secured by adding a few of its crystals to a mixture of sugar and strontium hydroxid solutions.
The disaccharate is precipitated as a granular substance when from two to three molecules of strontium hydroxid are added to a boiling sugar solution. The reaction is extensively used in separating the sugar from beet molasses.
164. Calcium Saccharates.—Three calcium saccharates are known in which one molecule of sugar is combined with one, two and three molecules of lime respectively.
The monosaccharate is obtained by mixing the sugar and lime in the proper proportion and precipitating by adding alcohol.
The precipitate is partly granular and partly jelly-like, and is soluble in cold water. The dicalcium compound is obtained in the same way and has similar properties. Both, on boiling, with water, form the trisaccharate and free sugar.
The tricalcium saccharate is the most important of these compounds, and may be obtained directly by mixing freshly burned and finely ground lime (CaO) with a very cold dilute solution of sugar.
The compound crystallizes with three or four molecules of water. When precipitated as described above, however, it has a granular, nearly amorphous structure, and the process is frequently used in the separation of sugar from beet molasses.
In the laboratory but little success has been had in using even the barium hydroxid as a chemical reagent, and therefore the reactions mentioned above are of little value for analytical purposes. In separating sugar from vegetable fibers and seeds, however, the treatment with strontium hydroxid is especially valuable the sugar being subsequently recovered in a free state by breaking up the saccharate with carbon dioxid. The technical use of these reactions also is of great importance in the beet sugar industry.
165. Qualitive Tests for the Different Sugars.—The analyst will often be aided in examining an unknown substance by the application of qualitive tests, which will disclose to him the nature of the saccharine bodies with which he has to deal.
166. Optical Test for Sucrose.—The simplest test for the presence of sucrose is made with the polariscope. A small quantity of the sample under examination is dissolved in water, clarified by any of the usual methods, best with alumina cream, and polarized. A portion of the liquor is diluted with one-tenth its volume of strong hydrochloric acid and heated to just 68°, consuming about fifteen minutes time in the operation. The mixture is quickly cooled and again polarized in a tube one-tenth longer than before used; or the same tube may be used and the observed reading of the scale increased by one-tenth. If sucrose be present the second reading will be much lower than the first, or may even be to the left.