182 Af. Bej'zelius on Hydracids, [Sept. 



was discovered by Wbhler. He found that wh^n sulphuretted 

 cyanuret of mercury is gently ignited in a glass vessel filled with 

 muriatic acid gas, or with sulphuretted hydrogen gas, there is depo- 

 sited upon the colder sides of the vessel a quantity of anhydrous 

 3ulphuretted prussic acid in the state of colourless transparent 

 drops, which, after a few seconds, become solid, and form 

 transparent, stellular, aggregated groupes of crystals. These 

 crystals rapidly undergo decomposition, cyanogen is disengaged, 

 and a pomegranate yellow,- opaque, uncrystalhne powder 

 remains. This powder is insoluble in water, and is in every 

 respect identical with the precipitate which is obtained when 

 liquid sulphoprussic acid is boiled in contact with the atmo*- 

 spnere. It appeai-s to be composed of prussic acid, combined 

 with twice tlie proportion of sulphur which exists in sulphc^ 

 prussic acid. That it is a hydracid, and not ati anhydrous 

 combination of sulphur and cyanogen, is proved by the circunxr 

 stance that when we heat it with potassium, a combination, 

 accompanied by ignition, ensues between the two substances, 

 hydrogen gas is evolved, and the compound which remains 

 consists of a mixture of the sulphuret and sulphocyanuret o^ 

 potassium. »,j 



Combinations of Hydracids with Saline Bases, 



A full exposition of the nature of the compounds of hydracids 

 with saline bases constitutes a most essential part of the theory 

 of these acids, because it furnishes the only means by which all 

 the apparent inconsistencies can be reconciled. In attempting 

 this explanation, two different views present themselves : either 

 the hydracid unites without decomposition with the oxidated 

 base, or its hydrogen decomposes the base, while the radicals 

 of both the acid and base enter into combination. Of these 

 views I consider the latter to deserve the preference ; for if a 

 solution of a salt obtained by saturating a hydracid v^^ith an 

 oxide be evaporated, it very frequently happens that there crys- 

 tallizes a reduced compound of the radicals of the acid and base, 

 wholly destitute both of hydrogen and oxygen; and when such 

 crystals contain water, that is, in the circumstances in which 

 they may be regarded as compounds of an oxidated base with 

 a hydracid, they frequently lose it in vacuo or in a dry atmo- 

 sphere, and effloresce exactly like substances which lose merely 

 water of crystallization. But these compounds of the radicals 

 of hydracids with the radicals of bases resemble so intimately 

 the salts which are formed by oxygen acids and oxides, that they 

 coincide with them in all their physical properties, as taste, 

 appearance, solubility in water, and in other liquids, and it 

 would be difficult, *vithout offering extreme violence to natural 

 arrangement, to class them among any other substances except 

 the salts. Gay-Lussac ascertained, for example, that if oxide 



