D. CHEMISTRY AND METALLURGY. 199 



fied carbon dioxide. He noted that at the temperature of 

 about 31 Centigrade the liquid in such a cavity disappeared 

 entirely, to return upon cooling. Dr. Andrews gives 30.92 

 Centigrade as the critical temperature of carbon dioxide, so 

 that there can no longer be any doubt concerning the nature 

 of the liquid under examination. 1 A,3Iarch 26. 



CAEBON MONOSULPHIDE. 



Sidot finds that when carbon disulphide, inclosed in her- 

 metically sealed tubes, is exposed for about two months to 

 the action of sunlight, brown flakes of the new monosulphide, 

 C S, are deposited. This substance, dried and purified, is a 

 chestnut-brown, tasteless, odorless powder of 1.66 specific 

 gravity. It is insoluble in water, alcohol, turpentine, or ben- 

 zol ; boiling ether or carbon disulphide dissolves traces of it. 

 Hot nitric acid dissolves the monosulphide to a red liquid ; 

 but chlorohydric acid is without action upon it. A boiling 

 solution of caustic potash takes it up freely, forming a black- 

 ish brown liquid, from which acids reprecipitate the sub- 

 stance. At 200 Centigrade the new sulphide decomposes, 

 sulphur distilling ofi", and carbon remaining behind. 18 C, 

 1875, Se2)tember 29. 



A NEW CLASS OP CYANIDES. 



Gaston Bong, studying potassium ferrocyanide and some 

 of its derivatives, has obtained a remarkable new double salt. 

 It is formed by treating a mixture of the common yellow 

 prussiate and potassium chlorate with sulj^huric acid until a 

 persistent blue color is produced. The resulting mass is 

 heated gently, extracted with water, neutralized with sodium 

 carbonate, boiled and filtered. This solution, by careful 

 crystallization in vacuo, yields black crystals, w^hich, readily 

 soluble in water, give it an intense violet color. The com- 

 pound may be regarded as the type of an entirely new class 

 of double cyanides, and its relation to well-known ferro- 

 and ferricyanides may be indicated by formulae : 



Potassium ferrocyanide KjFeCya 



Potassium ferrieyanide KaFeaCje 



New compound K^Fe^Cyia 



Thus, in this series, every added potassium atom needs a 

 doubling of all the other atoms in the molecule. The new 



