Mode of forming Cyanic Acid. 105 



urate of mercury to a decomposing- heat, and transmitted the strong 

 smelling gas that was disengaged, into barytes water. The cy- 

 anate of barytes, the salt of this class, with which he was best 

 acquainted, is the one most easily separable from impure prussic 

 acid. Much carbonate of barytes fell down, and at the same 

 time, a soluble prussiate of barytes was formed. The latter was 

 decomposed by a current of carbonic acid gas ; after which the 

 whole was heated, filtered, and evaporated. In this way he ob- 

 tained a perfectly white salt, in little scales, whose base was 

 barytes, and which being dissolved in acids, evolved a substance 

 of a vinegar odour, which excited a flow of tears, along with much 

 carbonic acid, and then ammonia by the addition of potash. It 

 exhibited in fact all the properties of cyanate of barytes, as de- 

 scribed by him in a former number of the Annals. 



Urate of mercury appears to yield a greater proportion of 

 cyanic acid, than an equal quantity of cyanide of mercury. 



When cyanogen is transmitted over heated carbonate of potash, 

 this becomes speedily fluid, then gradually yellow, and on cooling 

 it concretes into a bright yellow mass, which consists of cyanide 

 of potassium, mixed with carbonate and cyanate of potash. The 

 last salt is separable from the other two combinations, by boiling 

 alkohol. 



The following process answers best for preparing cyanate of 

 potash. Four parts of finely powdered cyanide of potash and 

 iron, intimately mixed with three parts of nitre, are to be gradually 

 projected into a crucible at dull ignition. At each addition a 

 white vapour arises which attaches itself to cool bodies, and con- 

 sists chiefly of cyanate of potash. The mass, still in a semi-fluid 

 state, is to be taken out of the crucible, to be pulverized when it 

 cools, and boiled in ordinary alkohol, which is to be poured off, 

 and allowed to cool. Cyanate of potash now crystallizes in small 

 plates. By re-dissolution in hot alkohol, crystallization, and pres- 

 sure (between folds of porous paper) the salt may be obtained 

 perfectly pure. About 20 parts of cyanate of potash may thus 

 be obtained from 100 of the triple prussiate. The plates of the 

 cyanate have a great resemblance to chlorate of potash. It is not 

 altered in the air. Its taste is very similar to that of saltpetre. 

 It is slightly soluble in cold alkohol; but very much so in water. 

 When heated it melts even at a temperature far under a red heat, 

 into a fluid as limpid as water, and is not decomposed even when 

 long kept in a state of ignition ; but if a drop of water be then 

 dropped into it, an extraordinary quantity of ammoniacal gas is 

 immediately exhaled. Treated with sulphuric acid, it is rapidly 

 decomposed into carbonic acid, sulphate of potash, and sulphate 

 of ammonia, which last is easily discoverable by the addition of 

 potash. With dilute acids, it exhales carbonic and cyanic acids, 

 xud an ammoniacal salt is formed. When the solution of cyanate 



