Chemical lecture experiments . NITRIC ACID PREPARATION 71. From potassium nitrate and sulphuric acid. — The gen-eral principle of using a stroug acid to drive a weaker out ofcombination is made use of in the preparation of nitric grams of powdered potassium nitrate are placed in a500 cc. glass-stoppered retort and 18 cc. of concentrated sul-phuric acid are carefully poured through a funnel upon themixture, care being taken to prevent any acid from gettinginto the neck of the retort. The retort is then gently agi- NITRIC ACID 223 tated to insure a thorough mixture of the ingredients
Chemical lecture experiments . NITRIC ACID PREPARATION 71. From potassium nitrate and sulphuric acid. — The gen-eral principle of using a stroug acid to drive a weaker out ofcombination is made use of in the preparation of nitric grams of powdered potassium nitrate are placed in a500 cc. glass-stoppered retort and 18 cc. of concentrated sul-phuric acid are carefully poured through a funnel upon themixture, care being taken to prevent any acid from gettinginto the neck of the retort. The retort is then gently agi- NITRIC ACID 223 tated to insure a thorough mixture of the ingredients. It isthen clamped so that it may be heated on a wire gauze, itsneck being thrust deep intoa 500 cc. flask partially im-mersed in water in a largecrystallizing-dish (Fig. 93).On applying a very gentleheat, nearly colorless nitricacid distils over and con-denses in the flask. KN08 + H2S04 = KHS04 + Fig. 93 500 cc. glass-stoppered retort; 500 cc. flask; crystallizing-dish ;KNO3. PROPERTIES 72. Intense acid reaction. —Nitric acid possesses a strongacid reaction which is readily shown by dipping a glass rodinto fuming nitric acid and then into a beaker containinga liter of water. Even at this great dilution the acidifiedwater will instantly redden a strip of blue litmus paper. 73. Action on organic matter. — Nitric acid attacks organicmatter, especially that of an animal nature, staining it yel-low. The simplest example of this property of nitric acidis the familiar fact that the acid stains the fingers large white feather has approximately the same composi-tion as the human skin, and when dipped into fuming nitricacid in a beaker is stained a brilliant yellow, while a con-siderable portion of the feather is actually destroyed. Onwashing off the excess of acid and dipping the feather intodilute ammonium hydroxide, the color is somewhat intensi-fied and becomes fixed. A
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