34 MR JOHNSTON ON PARACYANOGEN 



-^^^f 11. When a solution of cyanogen gas in water is allowed to stand for a con- 

 siderable time, a similai* black matter is deposited in smaller quantity. A por- 

 tion of this substance, for which I was indebted to the kindness of Professor 

 WoHLER, after heating to redness, to free it from water, ammonia, &c., burned 

 with oxide of copper, and the gases made to pass over a large surface of red hot 

 metallic copper, gave still distinct traces of nitric oxide, and 



263 vols, of the gas left 89 of nitrogen. 



110 — — 36.5 — 



96 — — 32 — 



69.5 — — 22.5 — 



12. A strong solution of caustic potash absorbs cyanogen gas very rapidly, 

 and when excess of the gas is present, speedily becomes coloured, forming a dark 

 reddish-brown solution, fi'om which a brown powder is precipitated on neutra- 

 lizing with an acid. Solution of caustic ammonia has a similar action, but I have 

 not yet prepared the matter in sufficient quantity by these processes to enable me 

 to analyze it. 



13. Ether absorbs cyanogen slowly, but in considerable quantity. The so- 

 lution in close vessels remains colourless. Left in an atmosphere of the gas for 

 thirty-six hours, it had absorbed sixteen times its volume, and began to be slightly 

 coloured. After several days the absorption appeared to cease at twenty-eight 

 volumes, it was of a brown colour, and had deposited a portion of a brown sedi- 

 ment. If water be added to the colourless solution, a black film gradually forms 

 at the common surface of the two fluids. — ^Liquid ammonia and caustic potash 

 cause a speedy deposition of the black matter. 



14. Alcohol absorbs cyanogen rapidly, and in large quantity. When per- 

 fectly saturated and set aside, the smell of cyanogen disappears, a sweet pene- 

 trating ethereal odour takes its place, and the solution becomes coloured. It is 

 now capable of taking up a second and larger doze of the gas, the smell of which 

 again disappears, on standing for twenty-four hours — the ethereal odour, mean- 

 while, becoming stronger and the colour darker. The addition of gas may now 

 be repeated, and by alternate changing and setting aside, an English pint of com- 

 mon alcohol may, in the course of a week or ten days, be made to absorb the 

 whole of the gas given off by four or five pounds of bicyanide of mercury. By 

 this time, also, a large deposit wUl be formed at the bottom of the bottle, and the 

 entire alcohol will have become dark and thick hke treacle. 



15. If this thick fluid be distilled, a colom-less product passes over, having 

 an ethereal odour, but from which water separates no ether, and which, on stand- 

 ing, gradually becomes dark coloured, and gives a further portion of the dark 

 brown or black sediment. After the lapse of some weeks or months, according 

 to circumstances, no farther evidence of decomposition shews itself, the deposi- 



