282 Notices of the Labours of Continental Chemists, 



acid being decomposed at the temperature at which the ac- 

 tion takes place; at the same time quadricarburet of hydrogen 

 is evolved. The decomposition may be expressed by the for- 

 mula 3 C + 2 N 2 H 6 = N 2 C 2 H 2 , N 2 H 6 + C H 4 . The ener- 

 getic action of charcoal on ammonia may be turned to ac- 

 count in preparing anhydrous prussic acid. For this purpose 

 dried ammonia is passed through a porcelain tube containing 

 small pieces of red-hot charcoal ; the escaping gases, containing 

 much prussiate of ammonia, are conveyed into dilute sulphuric 

 acid, warmed to about 50°; the ammonia is detained by the 

 sulphuric acid, and only prussic acid escapes, which is con- 

 densed in a vessel surrounded by a frigorific mixture. The 

 acid thus obtained is quite as pure as that from the decom- 

 position of cyanide of mercury by means of hydrochloric acid. 

 This action of carbon with ammonia may also be employed in 

 the preparation of the ferrocyanide of potassium ; the vapour 

 of the prussiate of ammonia is passed into a solution of caustic 

 potash, in which the hydrate of the protoxide of iron is sus- 

 pended. 



Similar experiments on the action of ammonia on red-hot 

 charcoal have been published by M. Langlois in the Annates 

 de Chim. et de Phys. 3ieme Sir. t. i. p. 117, which agree with 

 the above, with the exception that the gas which escapes at the 

 formation of the prussiate of ammonia, is stated to contain nei- 

 ther nitrogen nor carburetted hydrogen, but to be pure hydro- 

 gen. To explain the decomposition M. Langlois adopts the 

 notion, that one equiv. of ammonia, N 2 H 6 , becomes, on con- 

 tact with incandescent charcoal, N 2 H 2 + H 4 ; the two equiv. 

 of hydrogen are then replaced by two equiv. carbon to form 

 prussic acid, which immediately enters into combination with 

 one equiv. of undecomposed ammonia ; a portion of the hy- 

 drogen of the ammonia being replaced by carbon exactly as 

 the oxygen of the metallic oxides by chlorine, when exposed 

 with the latter to a high temperature. 0*114 of the salt gave 

 O^-tO cyanide of silver, corresponding to 0*068 prussic acid, 

 which gives the formula N 2 H 6 + C 2 N 2 H 2 . 



Double Cyanurets of Zinc with Alkalies and Earths. 



Samselius has found that these combinations may likewise 

 be obtained, (besides in the usual moist way, by dissolving cya- 

 nide of zinc in the alkaline cyanides,) by mixing the alkaline 

 cyanides with carbonate, or any other salt of the oxide of zinc, 

 as long as the cyanide of zinc is redissolved, upon which the 

 double salt is obtained on evaporation, at least, as far as may 

 be concluded from the action with cyanide of potassium. 

 Caustic ammonia dissolves cyanide of zinc, and soon deposits 



