THE USE OF LIQUID AMMONIA AS A SOLVENT 107 



Liquid ammonia is easily obtained commercially, as it is used 

 as the " working substance " in refrigerators. The ammonia 

 sold for this purpose is fairly free from impurity and can often 

 be used as a solvent without any further purification being 

 necessary. As is stated above, inorganic salts are, generally 

 speaking, less soluble in ammonia than in water; but there are 

 many exceptions — such, for example, as silver iodide, which is far 

 more soluble in ammonia than in water. Many of the ordinary 

 interactions of salts take place as in aqueous solutions, but 

 owing to differences in the order of solubilities in liquid 

 ammonia many actions take place in it which do not occur in 

 water. Thus, for example, calcium chloride is precipitated by 

 adding a solution of ammonium chloride to calcium nitrate in 

 ammonia. There are numerous interactions which only take 

 place in liquid ammonia, which are of especial interest owing to 

 the fact that they give rise to new classes of compounds analogous 

 to bases, acids and salts. 



Solubilities in Liquid Ammonia 



Liquid ammonia boils at — 3 3 ' 5 D C. and so it was not easy to 

 work with it in the days before vacuum-jacketed vessels were 

 in common use. A liquid which can be kept at ordinary 

 temperatures was prepared by Divers (i) 1 in 1873 by passing 

 dry ammonia over dry ammonium nitrate ; in this way a solution 

 of ammonium nitrate in anhydrous ammonia was obtained, of 

 which the boiling-point was as high as +25 C. This liquid 

 resembles pure ammonia in its solvent action on many sub- 

 stances and numerous solubility determinations were made 

 with it ; but more interest is attached to the work of Gore (2) 

 on solubilities in pure liquid ammonia. He investigated the 

 solubilities of many substances, both inorganic and organic, and 

 found that amongst the metallic salts the nitrates are generally 

 the most soluble, as is the case with aqueous solutions. The 

 chlorides, bromides and iodides are also most of them soluble 

 but there are many exceptions, one of the most striking being 

 calcium chloride. Oxides, carbonates, sulphides and sulphates 

 are generally insoluble, although many of the ammonium salts 

 form exceptions by being soluble. Amongst the elements, iodine^ 

 sulphur and white phosphorus were found to be soluble, also 

 the alkali metals which form blue solutions. Gore also found 



1 A list of references is given at the end of the article. 



