TRANSACTIONS OF THE SECTIONS. 53 



close crucible with carbonate of potash at a moderate red heat, cyanide in abundance 

 is always produced, which is never the case with pure charcoal, provided the tempe- 

 rature does not exceed redness. After some preliminary trials, the results of which 

 were unequivocal, a mixture of fifty grains of pure sugar-charcoal, and fifty grains of 

 carbonate of potash, obtained by gently igniting pure bicarbonate, was placed in a 

 porcelain tube fixed across a furnace, and maintained at a full red heat, while pure 

 nitrogen gas, very carefully prepared by acting on solution of ammonia by chlorine, 

 was slowly passed over the mixture. At the further extremity of the porcelain tube, 

 a small gas-delivering tube was arranged, dipping into a vessel of water. At the 

 commencement, the quantity of gas emitted by the exit end of the arrangement 

 greatly exceeded that passed into the tube : it had no odour, did not render lime- 

 water turbid, and burned with a bright blue flame, generating carbonic acid. After 

 some time the carbonic oxide diminished in quantity, until at length nitrogen alone 

 escaped. The tube, when cold, being examined, was found to contain a black 

 porous mass, which hissed and became very hot on the addition of water. A little 

 of the filtered solution gave, by " Schee'le's test," abundance of Prussian blue ; 

 another small portion, acidulated with nitric acid, gave a copious white precipitate 

 with nitrate of silver ; and the residue, distilled with dilute sulphuric acid (the addi- 

 tion of which scarcely occasioned efi'ervescence), afforded about half an ounce of tole- 

 rably strong hydrocyanic acid. Arrangements were made for repeating the experi- 

 ment, employing the nitrogen of the atmosphere in place of that artificially prepared, 

 the result of which was, as before, a black mass rich in cyanide of potassium. 



The amount of carbonate of potash converted into cyanide by direct absorption of 

 nitrogen, appears to depend very much on the temperature employed. In two trials, 

 at a full red heat, the quantity of carbonate converted amounted to 11 '5 and 12'5 

 per cent, of that employed. When, however, the temperature was raised to white- 

 ness, much above the melting point of copper, the production of cyanide appeared 

 much greater. 



When carbonate of soda was substituted for the potash-salt, cyanide was gene- 

 rated, but it seemed with much greater difficulty. The fact therefore appears to Mr. 

 Fownes to be established, that free nitrogen can at a high temperature combine di- 

 rectly with carbon, provided some metal or similar body be present, whose cyanide is 

 permanent under such circumstances. 



Abstract of a Letter from Prof. Liebig to Dr. Playfair. 



Some interesting results have been lately obtained in my laboratory. M. Schunk 

 has obtained a white crystalline substance, in large quantity, from the lichens which 

 are employed to prepare archil {Lecanora tartarea, &c.), by extraction with sether. 

 It differs from erythrine and the compounds described by Dr. Kane, in its insolubility 

 in water. With alkalies it behaves in a remarkable manner. It dissolves readily in 

 alkaline solutions, and is capable of being again precipitated by acids, if the solution 

 be recently made ; but if kept standing for some hours, acids produce no precipitate : 

 it has then been decomposed, and is converted to carbonic acid and orceine. If the 

 substance be dissolved in baryta-water, and the clear solution boiled, a large preci- 

 pitate of carbonate of barytes occurs, and the filtered solution gives, on evaporation, 

 large crystals of orceine. From this circumstance a number of phenomena on the 

 colour of lichens can be explained, which Dr. Kane has described in his work on that 

 subject. 



I have performed many experiments on the legumin in beans, and some other legu- 

 minous plants, and have arrived at the remarkable conclusion, that this body is iden- 

 tical with the casein in milk of animals. It has precisely the same composition, and 

 contains the same salts — phosphate of potash, potash, magnesia, lime and iron — as 

 the casein of milk. 



Dr. Will and Dr. Varrentrapp have devised an excellent method for determining the 

 amount of nitrogen in organic bodies : it is very exact and easily performed. The 

 substance is mixed with a quantity of caustic potash and hydrate of soda, and heated 

 in an ordinary combustion tube to redness. All the nitrogen in the substance escapes 

 as pure ammonia, which is condensed in a small and neat apparatus containing dilute 

 hydrochloric acid. This solution is mixed with chloride of platinum, evaporated to 

 dryness in a water-bath, and the excess of chloride of platinum is washed from the 



