ELISHA MITCHELL SCIENTIFIC SOCIETY. 19 



nearly to the surface of the mixed substances and having its other 

 end connected with a washing flask containing a strong solution of 

 iodium hydroxide ; the other just entered the cork and was con-' 

 nected w th a calcium chloride tube to which was joined a tube, 300l 

 m m long, filled with murcuric oxide. A smaller tube from the end of 

 this, dipped beneath a solution of potassium hydroxide. By means of 

 an aspirator, air was drawn through this system of tubes slowly and 

 at regular intervals for about two days. At the end of this time 

 the potassium hydroxide was tested with the ferroso-ferric solution 

 and no trace of prussian blue could be detected. The calcium 

 chloride and mercuric oxide tubes were then removed and air once 

 more drawn through into a solution of potassium hydroxide. On 

 testing this the reaction for hydrocyanic acid with the ferroso-ferric 

 solution was very clearly given. Here then was proof that hydro- 

 cyanic acid and no cyanogen was formed during the reaction. As 

 a confirmatory test, however, hydrochloric acid was added to a por- 

 tion of the potassium hydoxide through which the gas had been 

 drawn, then sodium hydroxide, and it was heated to boiling. No 

 ammonia could be detected. There was therefore no potassium 

 cyanate present and hence no cyanogen had entered the liquid. 



The aqueous solution of potassium cyanide can be kept unaltered 

 in closed vessels at ordinary temperatures according to Pelou/e and 

 rieiger^(Giuelin's Hand-book, vii, 415), but when boiled it is resolved 

 into ammonia and potassium formate. It is well known that a strong 

 smell of ammonia can be detected on opening a bottle containing 

 moist cyanide, but we have seen no mention of the formaticjn of 

 hydrocyanic acid from the cyanide by simple decomposition without 

 the aid of carbon dioxide or any strong acid. It was noticed during 

 these experiments that when moistened potassium cyanide was en- 

 closed in a test-tube and air aspirated over it for several days a 

 slight but distinct Prussian blue test was given by the solution of 

 potassium hydroxide through which the air after leaving the tube 

 wa-: drawn. Of course every precaution was taken to free the air 

 from all traces of carbon dioxide or acid. It was made to pass 

 through a wash bottle containing a concentrated solution of sodium 

 hydroxide, then through two V tubes filled with small lumps of 

 solid hydroxide, and lastly, fo have proof of the absence of carbon 

 dioxide, through a small tube containing limewater. passing thence 

 into the lube containing the cyanide. This experiiiient was repeated 

 at various temperatures ranging from 12^ — 18^ c. and always with 

 the same result. If the amount of moisture was small the depth 

 of color gotten in the ferroso-ferric test was slight. ]f about 1 c.c. 



