Licence: Public Domain Mark
Credit: Elements of human physiology. Source: Wellcome Collection.
Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.
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![A slight clouding occurs from precipitatioa of hydrate of copper oxide, which dissolves on shaking. On heating the fluid, if sugar he present, a yellowish precipitate of copper oxide takes place. 2. Bottger''s test. — An alkaline solution of hismutk is reduced hy sugar to hismuth suboxide, the oxide heing precipitated as an olive green and ultimately black powder. 3. Moore's test.—The fluid is boiled with caustic alkali, and becomes, if sugar be present, fir^t yellow, then brown, and then blackish. On the addition of nitric acid a smell of caramel is perceptible. 4. Mulder atid Neubauer''s test consists in the addition of a sufficient quantity of a solution of indigo carmine to give the saccharine solution a faint blue tint, and applying sodium carbonate; on applying heat the colour changes to green, purple, and red. On agitation with air the fluid recovers its blue tint. 6. Runge's test.—Saccharine solutions, when evaporated to dryness with sulphuric or hydi'ochloric acid in a water bath in a porcelain capsule, leave behind a black shining residue. 6. Silver test.—Diluted solution of grape sugar, on being boiled with silver nitrate and ammonia, leaves a metallic deposit on the surface oi the vessel. Alcoholic solution of grape sugar, mingled with alcoholic solution of caustic alkali, causes a precipitation of a compound of alkali and sugar in the form of white flocculi. Fa.tS«—The fats are ethers derived from the triatomic alcohol glycerin C^B.^{OW]^. They are widely distributed both in plants and in animals. They contain very little oxygen. They are soluble in ether, benzol, chloroform, and in boiling alcohol. Dropped on paper they give a characteristic grease spot. Shaken up with colloid sub- stances they give an emulsion. Heated with water above steam heat, or exposed to the action of certain animal ferments, as that of the pancreas, they take up water and split into glycerin and free fatty acids. When these essential fats are boiled with solutions of the alkaline hydrates or carbonates, they undergo the process of saponification, decomposing as before into glycerin, and the fatty acids, but the latter immediately combine with the alkaline metal to form a soap, which is, in fact, a](https://iiif.wellcomecollection.org/image/b21210433_0017.jp2/full/800%2C/0/default.jpg)
