192 



fumes of nitrous acid are evolved. The residue is a strongly acid 

 syrup, which becomes finally crystalline. It is repeatedly dissolved 

 in water and evaporated on the water-bath in order to expel the 

 nitric acid. Thus purified, the new acid is dissolved in boiling water, 

 neutralized with pure carbonate of barium and separated from sul- 

 phate of barium. On cooling, the barium-salt of the new acid cry- 

 stallizes. It is soluble in boiling water, less so in cold water, and 

 almost insoluble in alcohol, by means of which it may be precipitated 

 from its solution in water. 



On examining the appearance and deportment of this salt, Dr. 

 Hofmann, in whose laboratory I performed these experiments, at 

 once recognized the identity of this compound with the barium-salt 

 of disulphetholic acid which he and Mr. Buckton have lately 

 discovered. 



This view was fully confirmed by the analysis which I made. 



The composition of the barium-salt, dried at 160, is represented 

 by the formula 



C 4 (H 4 Ba 2 )S 4 12 . 



The potassium salt of this acid is readily soluble in water ; it crystal- 

 lizes easily, and is likewise precipitated by alcohol from its solution 

 in water. Dried at 100 C., it contains 



C 4 (H 4 K 2 )S 4 12 . 



At 1 60 it suffers no decomposition ; when exposed to a higher tem- 

 perature, however, it blackens and intumesces, empyreumatic sub- 

 stances being evolved. 



It is obvious that this bibasic acid stands in the same relation to 

 ethylene as the monobasic ethylsulphurous acid to ethyl. 



The origin of the two acids is perfectly analogous, the latter acid, 

 according to Mr. Muspratt, being obtainable also by the action of 

 nitric acid upon sulphocyanide of ethyl. 



Sulphocyanide of ethyl, C 4 H 5 Cy S 2 , produces ethylsulphurous 

 aeid,C 4 H 3 ,H, S 2 6 . 



Sulphocyanide of ethylene, C 4 H 4 Cy 2 S 4 , produces ethylensulphu- 

 rous acid, C^^ 2H, 2S 2 O 6 . 



This reaction appears to throw some light upon the constitution 

 of polybasic compounds. The compounds of monatomic molecules 

 of the hydrogen-group with elements or compound radicals of the 

 oxygen-group, are all remarkable for the simplicity of their construe- 



