Hydro cyanate

(Chem.) A salt resulting from the union of hydrocyanic acid with a base. Hydrocyan'ic Acid, CYANHY'DRIC ACID, PRUS'SIC ACID, n. [From hydrogen and cyanogen.] ( Chem.) This important acid is composed of equal volumes of hydrogen and the compound gas cyanogen, which in this instance comports itself like one of the halogens, chlorine or bromine. It is prepared in an analogous manner to hydrochloric acid, by submitting a cyanide to distillation with a strong acid. Cyanide of pota ium is placed in a retort, and half its weight of dilute sulphuric acid is poured upon it. At first the distillation proceeds spontaneously from the heat developed. Equiv. 27. Sp. gr. 0-9476. Combining volume 4. Form. HCy. with a cork and bent tube (Fig. 1339), and on the add i-eral, found in stalactitic forms at Vesuvius. Sp.gr. 2:49. Fig . 1339. PREPARATION OF SOLUTION OF HYDROCHLORIC ACID. tion of sulphuric acid, and the application of gentle heat, the gas pa es over into a second ve el containing water, by which it is at once absorbed. For collecting it in quantity, a series of Wolfe's Bottles, q. v., is used. In this experiment the hydrogen of the water, combined with the sulphuric acid, unites with the chlorine of the salt, while the sulphuric acid unites with the sodium of the salt, to form sulphate of soda, or Glauber-salt. The solution, when pure, is a colorle solution, but the "muriatic acid" of commerce is generally of a straw color, from the presence of impurities. H. A. is a constituent of the gastric juice , q. v., and the gas is a common volcanic product. Its presence in any liquid may be detected by adding a solution of nitrate of silver. A white, curdy precipitate of chloride of silver is formed, which di olves in ammonia, and blackens on exposure to the light. In the manufacture of soda-ash, H. A. is formed in large quantities, and when allowed to escape into the air, produces an acid mist which ruins the surrounding vegetation. To prevent this, immense chimneys have been erected to discharge the gas at a greater distance from the ground. One near Liverpool is 495 feet high. These do not remedy the evil, and it is found nece ary to condense the gas in water. H. A. was first obtained as a pure gas by Priest ley in 1772, but its solution in water had long been known as spirit of salt , muriatic acid , (from Lat. muria , sea-water, brine.) and marine acid. Its more proper chemical name is chlorohydric acid . Its composition was ascertained by Davy, In 1810.