42S Miscdlarieom Intelligence. 



in this respect, like calcined alum, A smaller part of the acid is de- 

 composed during the sublimation, but without leaving any charcoal, 

 but disengaging a mixture of gases which, apparently, are azote 

 and carbonic acid, possessing, in a very great degree, the penetra- 

 ting odour of cyanous acid. If, during the operation, the neck of 

 the retort and the receiver are cooled considerably, etherial striae 

 are deposited within, which are liquid cyanous acid (formerly 

 called cyanic acid), and which, tQ this time, had neVier been obtained 

 in a separate state. 



The liquid is limpid, colourless, very volatile, having a very pene- 

 trating odour, and strongly ailecting the eyes. In contact with 

 water, it is immediately decomposed with the evolution of heat, 

 producing carbonate of ammonia. If the products of the distilled 

 cyanic acid be sent into a moistened recipient, the water and the 

 cyanous acid immediately become carbonate of ammonia; but if 

 the vapours be sent into caustic ammonia, the evaporated liquid 

 gives colourle^ crystals of urea. The same substance is formed in 

 a bulky vegetation at the mouth of the retort if the recipient be 

 merely moistened with liquid ammonia. Urea appears to be formed 

 even with pure water, for if the recipient contain only a few drops 

 of water, soon after the vapours are sent into it, the former evolves 

 gas, which is no doubt carbonic acid, from the carbonate of ammo- 

 nia formed; it is finally decomposed, and becomes urea by the 

 action of a further portion of the cyanous acid. M. VVohler re- 

 marks, that when cyanites- are decomposed by aqueous acids, the 

 pungent odour analogous to nitric acid, which the carbonic acid 

 evolved possesses, is due to a small quantity of cyanous acid which 

 is volatilized with the carbonic acid without being decomposed. 



The accordance of the cyanic acid in properties with that usually 

 called the pyro-uric, as well as the physiological analogy between 

 urea and uric acid, induced M. Wohler to examine the pyro-uric 

 acid and other products of the distillation of the uric acid. He 

 used the excrements of snakes, which, for their purification, were 

 digested for 24 hours in muriatic acid, to separate phosphate of 

 lime and ammonia, and being then well washed and dried, were 

 distilled at a red heat. The pyro-uric acid then proved to be cyanic 

 acid. These facts immediately suggested that urea might be 

 produced by the distillation of uric acid, i. e., from the ammonia 

 which is evolved in these circumstances, and from the decomposition 

 of the cyanic acid formed. Nothing was easier than to verify this 

 conjecture, and to prove that the essential part of the product, 

 arising from the decomposition of uric acid by heat, was half cyanic 

 acid and half urea. 



On distiUing well-dried uric acid no liquid product was obtained, 

 but a very large quantity of hydrocyanic acid. The sublimate is at 

 first soft, but soon hardens in the air ; it is of yellow or clear brown 

 colour, and smells strongly of hydrocyanate of ammonia: here and 

 there are appearances of thin colourless crystalline plates : it is 

 impossible to separate the cyanic acid in its pure state, without 



