THE USE OF LIQUID AMMONIA AS A SOLVENT 117 



Reference has already been made to the interactions of 

 ammono-acids and ammono-bases. Amongst the products that 

 have been obtained in this way and whose composition has 

 been confirmed by analysis are : 



CH S . CO. NHK + (NH 3 )n 

 QHs.CHj.CO.NHK + (NH,)n 

 C (i H s . CO. NHK and C 6 H 5 . CO . NK, 

 C 6 H 5 .S0 2 . NHK and C 8 H, • SO, . NK 2 . 



The method of preparing these is obvious from the formulae. 

 In each case an ammonia solution of the acid amide is added 

 to a solution of potassium amide, whereby some of them are 

 precipitated whilst others are caused to crystallise by concen- 

 trating the solutions. 



A general method of preparing cuprous salts by means of 

 liquid ammonia has been suggested by Joannis (15). Cuprous 

 oxide is added to an ammonia solution of the ammonium salt of 

 the desired acid : 



2NH 4 X + CuX> = Cu 2 X 2 + :NH 3 + H a O. 

 In this way he prepared cuprous formate and benzoate. 

 Another example of synthetic work in liquid ammonia is that 

 of Emil Fischer (16), on the conversion of alkyl derivatives of 

 malonic ester into the corresponding amides. He found that 

 the yield of amide obtained when using liquid ammonia was 

 less than when using saturated alcoholic ammonia in the case of 

 the simple ester. On the other hand the alkyl derivatives gave 

 a better yield with liquid ammonia. 



The great solubility of ammonium nitrate in liquid ammonia 

 has been made the subject of a patent for the separation and 

 purification of ammonium nitrate from mixtures containing 

 sodium and potassium nitrates. Other patents that make use of 

 the solvent action of liquid ammonia are for the purification of 

 crude anthracene and anthraquinone and for the purification 

 of cyanides. The former depends upon the insolubility of 

 anthracene in liquid ammonia, most of the impurities being 

 readily soluble ; in this way it has an advantage over the 

 use of sulphur dioxide, which dissolves actually more of the 

 anthracene than of the impurities and hence makes the process 

 costly and inefficient. The latter process mentioned above 

 depends upon the different solubilities of various cyanides in 

 liquid ammonia and can be used for the separation of sodium 

 from potassium cyanide, the latter being more soluble. 



