•1825.] M, Berzelius on Hydracids, 'fgfl 



selves into two classes, viz. acids with a simple, and acids with a 

 compound radical. 



■^ To the j^'rs^ of these classes belong : 1. Sulphuretted hydrogen 

 gas; 2. Seleniuretted hydrogen gas ; 3. Telluretted hydrogen gas; 

 4. Hydrochloric acid; and 5. Hydriodic acid; chlorine and iodine 

 being regarded as simple substances. My principal arguments 

 against the new theory of the constitution of muriatic acidvv^ere 

 founded upon the little analogy which subsisted between it and 

 its combinations, and the hydracids and their salts, in so far as 

 the latter were known at the time of its first promulgation. The 

 subsequent discovery, however, of many hydracids, and in par- 

 ticular of those with a compound radical, has developed the 

 analogy between muriatic acid and the hydracids so completely, 

 that these objections can no longer be considered as valid. 



To the latter class ; namely, hydracids with a compound radi- 

 cal, belong: 1. Prwmc «nc? (cyanuretted hydrogen) ; 2. Sulpho- 

 prussic acid (sulphuretted cyanogen combined with hydrogen) ; 

 3. Ferroprussic acid (a combination of cyanuretted iron with 

 cyanuretted hydrogen); and to these may be added, 4. Another 

 compound not so accurately known, whose constituents, 

 although differently proportioned, are also cyanogen and 

 sulphur. 



Sulphoprussic acid may be obtained by mixing a solution of 

 sulphocyanuret of potassium in a minimum of water with con- 

 centrated phosphoric acid, and distilling in a retort with a gen- 

 tle heat. The hydracid is volatihzed, and condenses in the 

 receiver. The potassium in this experiment, in order to com- 

 bine with the phosphoric acid, oxidizes itself at the expence of 

 water, and the hydrogen thus set at liberty unites at the same 

 instant with the sulphuretted cyanogen. 



Sulphoprussic acid is so constituted, that its elements, if 

 reduced to the gaseous state, would all occupy the same volume ; 

 or it is composed by weight of hydrogen 1*68, azote 23-85, car- 

 bon 20'30, and sulphur 54*17. Its saturating capacity, as is the 

 case with all hydracids, is such, that it combines with a quantity 

 of a base whose oxygen is exactly sufficient to convert its hydro- 

 gen into water. 



The radical of this acid, salphiiretted cyanogen, has not 

 hitherto been isolated, and is known only in the compounds 

 which it forms with hydrogen or with metals. When we attempt 

 to obtain it by distilling a sulphuretted metallic cyanuret, it 

 always undergoes decomposition : a metallic sulphuret contain- 

 ing a minimum of sulphur remains, and sulphuret of carbon, 

 cyinogen, and azote are disengaged. 



But cyanogen combines also with a double proportion of sul- 

 phur, and forms a bisulphuret, which in union with hydrogen 

 affords a hydracid, differing in composition from the foregoing, 

 and capable, like it, of combining with metals. This new acid 



