MELLON, CYANIL1C ACID. 9 ( JD 



PRODUCTS OF THE DECOMPOSITION OF SULPHOCYANOGEN. 



Metasulphocyanogen^ C 12 N 6 S 12 H 3 O (Parnell). This is the 

 yellow substance precipitated by the action of chlorine on 

 sulphocyanide of potassium in solution, with formation of 

 chloride of potassium. It is also formed by the action of nitric 

 acid upon the same salt. Metasulphocyanogen dissolves entirely 

 in a solution of caustic potash. An acid added to this solution 

 throws down a lemon yellow precipitate, with a small quantity 

 of a black matter, which has not been fully examined. The 

 yellow substance is the hydrothio cyanic acid of Mr. Parnell, of 

 which the probable formula is C 10 N 5 S 12 H 6 O 2 ==H 4 ,Cy 5 S 12 -h 

 2HO. The neutral thiocyanides contain 4 atoms of metal in 

 the place of H 4 , and when insoluble are yellow, while the 

 thiocyanides combined with metallic oxide are black.* 



Mellon, C 6 N 4 (page 428). This is the fixed residue which 

 remains as a yellow powder, on heating dry metasulphocyanogen 

 to low redness in a glass flask, sulphur and bisulphuret of 

 carbon being volatilised at the same time. It was discovered 

 by M. Liebig, who supposed 4 atoms of sulphocyanogen 

 (C 8 N 4 S 8 ) to be resolved into 1 atom of mellon (C 6 N 4 ) 4 atoms 

 of sulphur (4S) and 2 atoms of bisulphuret of carbon (C 2 S 4 ). 

 But Mr. Parnell has observed the appearance in the decomposi- 

 tion of metasulphocyanogen, of water, sulphuretted hydrogen, 

 and hydrosulphocyanic acid, in addition to the products above. 

 He supposes three equivalents of metasulphocyanogen to be 

 resolved into four of mellon, C 24 N 16 ; two of hydrosulphocyanic 

 acid, S 4 C 4 N 2 H 2 ; four of sulphuretted hydrogen H 4 S 4 ; eight of 

 bisulphuret of carbon, C 8 S 16 ; twelve of sulphur S 12 , and three 

 of water H 3 O 3 . 



Mellon is insoluble in water, alcohol, and dilute acids ; is 

 decomposed at a bright red heat into three volumes of cyanogen 

 and 1 volume of nitrogen. It is a salt-radical, combining 

 directly with potassium, with ignition and formation of mellonide 

 of potassium ; with hydrogen it forms hydromellonic acid. 



Cyanilic acid, C 6 N 3 H 3 O 6 (Liebig). Mellon is decomposed by 

 the prolonged action of boiling nitric acid, with disengagement of 



* Philosoph. Mag. 3rd. Series, vol. 17, p. 249. 



