( 1^2 ) 



solutions possess hjdroxyl ions; the presence of water greatly favours 

 this catalysis. 



If an attempt is made to isolate the evidently formed cyanohydrin 

 by distillation under reduced pressure it is again resolved for the 

 greater part into its components. If, hovs^ever, the action of the 

 potassium carbonate is stopped by means of a few drops of sulphuric 

 acid, the mixture on being fractionated in vacuo first yields a 

 distillate consisting of hydrocyanic acid and acetone and then the 

 nitrile; by a second distillation this may be obtained in such a state 

 of purity that silver nitrate with nitric acid no longer gives a 

 precipitate of silver cyanide. 



Traces of a base are, hoAvever, sufficient to again partially resolve 

 the pure nitrile into its components, which in this case is, of course, 

 accompanied by a fall in temperature. 



Theory demands that the same equilibrium should be reached 

 whether we start from one mol. of acetone plus one mol. of hydrogen 

 cyanide or from pure cyanohydrin. In order to check this it is not 

 necessary to determine the equilibrium both ways by analysis; the 

 easiest plan is to measure some physical constant; for this I chose 

 the refraction. 



Found, starting from a mixture of acetone (i mol.), hydrogen 

 cyanide (1 mol.) and a trace of potassium hydroxide ?iz)^' = 1,39721. 



Found, starting from the pure nitrile aiid a trace of potassium 

 hydroxide w/)^^ = 1,39818. 



It having been thus ascertained that it makes no difference from 

 what system w^e start, it became important to express the equilibrium 

 in figures. 



For praiitical reasons I always started from the nitrites ; about 

 one gram of the compound and 0,2 milligr. of potassium hydroxide 

 (in a lOVo solution) were introduced into a tube, which was then 

 sealed and immersed in a beaker containing a solution of silver 

 nitrate acidified with nitric acid, and the Avhole was then suspended 

 in a thermostat for some hours. 



If now the tube is broken the nitric acid at once neutralises the 

 potassium hydroxide and the free hydrocyanic acid will be precipi- 

 tated as silver cyanide. Tiie liquid is decanted, the precipitate is 

 dissolved in potassium cyanide and the silver deposited electrolytically 

 in the usual manner. In this way it was found that one mol. of 

 acetone and one mol. of hydrogen cyanide combine at 0° to the 

 extent of 94,15»/ „, at 25» to the extent of 88,607o. 



For ethylmethylketone these values are, respectively 95,577o a»d 

 90,36»/o; for diethylketone 95,907„ and 91,297,. 



