3875. Tests for Nitric Acid

3875.    Tests for Nitric Acid. It stains the skin yellow. "When mixed with a little muriatic acid or sal-ammoniac, it acquires the power of dissolving gold leaf. "When mixed with dilute sulphuric acid, and poured on a few fragments of zinc or iron in a tube, the evolved gas burns with a greenish white flame. Substitute alcohol for zinc in the last test. Morphia, brucia, and strychnia give it a red color, which is heightened by ammonia in excess. When placed in a tube, and a solution of protosulphate of iron cautiously added, a dark color is developed at the line of junction, which is distinctly visible when only 1/24000 part of nitric acid is present. When mixed with a weak solution of sulphate of indigo, and heated, the color is destroyed.

3876. Dilute Nitric Acid

3876.    Dilute Nitric Acid. Mix 3 troy ounces nitric acid specific gravity 1.42 in a glass vessel with sufficient distilled water to make the dilute acid measure 1 pint. The specific gravity of officinal dilute nitric acid is 1.068, U. S. Dis.

3877. Fuming Nitric Acid

3877.     Fuming Nitric Acid. The red fuming nitrous or nitric acid of commerce is simply nitric acid loaded with nitrous or byponitric acid. It may be thus prepared: Put into an iron or stoneware pot, nitre or nitrate of soda, add rather more than half its weight of strong sulphuric acid, and lute on a stoneware head. The vapor is conducted into a series of two-necked stoneware vessels, containing each 1/6 of their capacity of water. The acid is usually obtained of the density of about 1.45. It is colored with nitrous acid gas, forming what is commonly, but improperly, termed nitrous acid. By gently heating the colored acid in a retort, the nitrous acid is driven off, and the acid remains nearly colorless, usually of the density of 1.38 to 1.42.

3878. Tire's Table of Percentage of Nitric Acid

3878. Tire's Table of Percentage of Nitric Acid. This table is useful for finding the strength of dilute acids solvent for gold.