Analytical Chemistry - Tapa blanda

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1895 edition. Excerpt: ... cupric ferricyanide. The silver salt is orange-yellow, and soluble in ammonia (decomposes when boiled). The remaining properties of hydroferricyanic acid are similar to those of the foregoing acid. Nitric Acid § 98. Nitric acid, HN03, is a liquid which boils at 86 C., undergoing partial decomposition at the same time; its sp. gr. at 14 C. = 1'52. It acts as an energetic oxidising agent, and in yielding its oxygen to other bodies is converted into lower oxides of nitrogen. Nitric acid is a solvent for many metals, and in its action upon them evolves either hydrogen (with zinc, etc.), which reduces the acid to nitrous oxide and ammonia, or nitric oxide (with copper, silver, etc.) The application of these properties in analysis is given below. Nitric acid is completely reduced to ammonia by the action of hydrogen in alkaline solution; i.e., by that of zinc, or, preferably, of aluminium, and potassium hydroxide. The normal nitrates are readily soluble in water; the basic salts of some of the metals, however, as well as the salts of certain organic bases, dissolve with difficulty. When ignited, the nitrates decompose, losing oxygen and passing into the oxide of the metal (employed in oxidation-reactions). Reactions of Nitric Acid and Nitrates.--As nitric acid forms no insoluble salts (except with some organic bases), its detection is effected exclusively by oxidation-reactions. These are all applicable to quantitative analysis. The reactions in which nitric oxide is formed are especially characteristic. Formation of nitric oxide. Action on copper.--To detect nitric acid by this reaction we use the property which the nitric oxide evolved possesses of turning to brown fumes in the air (union with oxygen: N02 is formed): 3Cu + 8HN03 = 2NO +...