On a New Compuex Copper CyaANoGEN CoMPOUND. 
By A. R. MIDDLETON. 
(Preliminary Note.) 
When a cold concentrated solution of KCN is added to a cold con- 
centrated solution of cupric chloride or sulphate, but not nitrate, greenish 
brown cupric cyanide is precipitated; the precipitate dissolves on fur- 
ther addition of KCN with formation of a claret red to violet red com- 
pound, much resembling potassium permanganate solution. Further addi- 
tion of KCN destroys the color, with precipitation of white cuprous cyan- 
ide (presumably), which then dissolves in excess of KCN. First addition 
of concentrated cupric salt solution, or the solid salt, to concentrated 
KCN solution produces a brilliant violet color, instantly destroyed by fur- 
ther addition and quickly disappearing on standing. Further additions 
of copper salt give the red compound, provided the solution is kept nearly 
at 0°; otherwise cyanogen is evolved and the red compound is not formed. 
If the solutions are too concentrated or too dilute, the red compound is 
not formed. Solutions about one-half saturated appear to give the com- 
pound most readily and in largest amount. 
Search through the available literature has revealed no reference to 
such a compound. It is quite unstable, decomposing to a brown solution 
on standing in a warm room over night; is instantly decomposed by 
strong and weak acids and bases and by pyridine; soluble in alcohol, but 
insoluble in chloroform, ether, benzene, toluene and carbon tetrachloride. 
Attempts to crystallize out the compound are in progress, and at the time 
of writing appear promising. The method pursued is as follows: Solid 
-CuCl,.2H,O was added in small amounts to KCN solution about one-half 
saturated, with constant shaking in ice water. After the red color reached 
a maximum, the solution was filtered, three volumes of 95% alcohol added 
and placed in the icebox in an exhausted desiccator. After 24 hours white 
opalescent scales separated, which, after washing with alcohol and ether 
and drying, present a metallic appearance somewhat resembling tinfoil. 
These contain copper and may be cuprous cyanide. The solution retained 
its red color unchanged and it is hoped that the compound can be crystal- 
lized out in form suitable for analysis. 
Purdue University, 
Lafayette, Ind. 
