44 MR JOHNSTON ON PARACYaNOGEN, 



14. Tlie second portion analyzed was thrown down from an acid solution. 

 10.88 grs. burned with bi-chromate of potash, and the gases made to pass over 

 red hot copper, gave 4.62 of carbonic acid and 1.09 grs. of water. 



10.87 grs. dissolved and boiled in aqua regia, and precipitated as before, gave 

 7.56 gi-s. of bi-sulphuret of mercury = 60.003 per cent, of metallic mercury. 



These give for the constitution of the anhydrous salt, 



(1-) (2.) 



Cai-bon, .... =13.094 



Nitrogen, . . . = 15.163 



Oxygen, . . . . = 2.141 



Protoxide of Mercury, = 69.602 . . 69.3738 



Boiled in diluted nitric acid, and dried in vacAio, the salt gave me 61.13 per 

 cent, of mercury : it had therefore undergone little change. 



A neutral compound (C8N4O + HgO) would contain 15.088 of carbon and 

 64.958 of protoxide of mercmy per cent. 



The difference, amounting to 2 per cent, in the quantity of carbon obtained 

 by analysis, may be accounted for by supposing it to contain a portion of the 

 basic salt 



VII. Paracyanate of Silver. 



1. When metallic silver is introduced into a solution of paracyanic in ni- 

 tric acid, a yeUowish-bro^vn powder falls down as the silver dissolves. A simi- 

 lar precipitate is obtained by dissolving solid nitrate or carbonate of silver in such 

 a solution ; and the more neutral the solution is rendered, the more completely 

 is the paracyanate throAvn down. If allowed to stand in this acid solution, the 

 precipitate sometimes forms minute prismatic or acicular crystals of a deep red 

 colour, grouped into small radiated globides. The supernatant liquid still retains 

 much of the salt in solution, a large portion of which is thro-\vn down as a beau- 

 tiful bulky yellow powder, on the addition of water. After it ceases to be 

 troubled by further dilution, the nitrate of protoxide of mercury throws down a 

 copious precipitate of paracyanate of mercury, shewing how much less soluble it 

 is than the salt of silver. 



2. The paracyanate of silver is precipitated by caustic ammonia from its so- 

 lutions in acids ; but the precipitate does not dissolve in an excess of the alkali. 

 Even when boiled in it, no sensible change is produced. The solution, indeed, 

 acquires a yellow colour, but contains no silver. 



3. It undergoes no sensible alteration in the sun's rays. 



4. It is soluble in hot dilute nitric acid, from which it partly separates again 

 on cooling. 



5. In the air, it may be heated to 300° F., without much change of colour. 



