AND THE PARACYANIC ACID. 33 



it was not a definite compound, and that the quantity of carbon was variable. 

 The presence of some impurity had probably interfered with the accuracy of his 



results. 



7. While on a visit to that eminent chemist at Giessen in the month of Oc- 

 tober 1835, he did me the favour to repeat his analysis in presence of Professor 

 PoGGENDOBF and Dr Gregory, and with a result on this occasion perfectly ac- 

 cording with my own. Thus, burned with oxide of copper, and the gases sepa- 

 rated by caustic potash — 



99 vols, left 32.6 vols, of nitrogen. 

 92.9 — — 30.1 — — 



293 — — 98 — — 



Another portion burned with bichromate of potash, a method lately suggested by 

 LiEBiG, gave the gases in a like proportion. Thus — 

 94.5 vols, left 33.5 nitrogen. 



129 43 — 



108 SQ — 



175 58.5 — 



8. My attention being thus recalled to the subject, I have since my return 

 prepared this substance by a variety of processes ; and have found, that not only 

 has it, when pure, the same composition as cyanogen, but that, Mice it, it also ex- 

 hibits with other substances many interesting reactions, and is capable of com- 

 bining with oxygen to form a new cyanic acid. 



9. Pure bicyanide, prepared by saturating prussic acid with peroxide of mer- 

 cury, reduced to powder, carefully dried and decomposed in a retort gradually 

 heated to redness, left a hght bulky powder, which, when burned with oxide of 

 copper, gave a gas, of which, treated with caustic potash, 



102 vols, left 35 of nitrogen 

 86 — — 29 — 



87.5 — — 29.5 — 

 This substance is remarkably difficult to bum. The quantity of nitrogen 

 present is so great that I have only once or twice succeeded in burning it with- 

 out the formation of a sensible quantity of nitric oxide. 



10. When strong prussic acid is set aside, it speedily decomposes, and depo- 

 sits a black powder in considerable quantity. Dried in vacuo over sulphuric acid 

 or at 212° F., this substance stDl gives off, when heated in close vessels over a 

 lamp, water, carbonic, and hydrocyanic acids, and ammonia. The black matter 

 that remains, burned with bichromate of potash in large excess, gave a mixture 

 of carbonic acid and nitrogen in the proportion of 2 to 1. Thus, 



97.5 vols, left 32 of nitrogen. 92.5 left 30 



95 31 — 90.5 - 29.5 



VOL. XIV. PART I. ^ 



