42 retort — 1884. 



readiness with which it can be removed from a componnd in the form of 

 water. Laurent thus concludes that oxides, hydrogen salts, and other 

 salts may with perfect propriety be classed together. 



Acid and Basic Salts. 



Houelle was the first to call attention to the fact that a given acid 

 and base can combine in different proportions. He prepared the salt 

 now known as KHS0 4 from potassic sulphate (tartre vitriole), and in- 

 vestigated its properties. He distinguished three different classes of salts. 



1. He calls 'neutral salts with an excess or superabandance of acid,' 

 salts which, besides the amount of acid which makes them quite neutral, 

 have an additional quantity of acid combined with them, and he knows 

 that this excess of acid has its point of saturation. Such salts, he says, 

 are as a rule more soluble thau the corresponding salts of his third class. 



2. What we call neutral salts he calls ' sels neutres parfaits,' or ' sels sales.' 



3. The third salts he calls ' neutral salts with the smallest possible 

 quantity of acid.' At first sight these classes seem to correspond with 

 what we now call acid, neutral, and basic salts, but Rouelle's examples 

 show that this is not the case. The only acid salts which he seems to 

 have known is the hydric potassic sulphate which he was the first to 

 prepare, and he puts in the same class with it mercuric chloride and other 

 persalts, while calomel is given as the typical instance of a salt with the 

 smallest possible amount of acid. This confounding of hydrogen double 

 salts with salts containing as largo an amount of acid as the base can 

 saturate continued up to the end of the century. 



1787. — In course of time, however, more salts of the two abnormal 

 classes were discovered. In the 'Morveau-Lavoisier' nomenclature, salts 

 of the acid class were called acidulous salts, thus: KHSO.j=sulphate 

 potassique acidule, while salts with an excess of the basic constituents 

 were called alkaline, or supersaturated salts. Salts generally are called 

 neutral salts. These terms were translated directly into English in 

 Pearson's translation of 1794. 



In an essay on ' Chemical Nomenclature,' published in 1796 by 

 Stephen Dickson, he proposes to denote the predominance of acid and 

 base respectively by prefixing the prepositions ' super-' or ' sub-' to the 

 adjective the name of the acid. 



Thus:— 



KHSO.[=supervitriolated vegetable alkali. 

 Cu 2 C] 2 =submuriated copper. 



1809. — In Murray's ' System of Chemistry ' we find that a distinction 

 is at last made between the relation of K 2 S0 4 to KHSO„ and that of 

 HgCl 2 to Hg 2 Cl 2 . He says that submuriate is net a good name for this 

 last salt, as it contains enough acid to make it neutral. He does not, 

 however, propose a systematic name for this substance, but calls it mild 

 muriate of mercury. Similarly, he rejects the name of super-sulphate of 

 iron, and distinguishes the two sulphates as red and green sulphates. 



1810. — In the fourth edition of Thomson's treatise, we find yet 

 another method of naming these salts. Thomson, following Lavoisier's 

 theory of oxygen acids, considers that the difference between calomel and 

 cox-rosive sublimate is that in the latter the mercury is in a more highly 

 oxidised condition. He therefore calls HgCl 2 oxymuriate of mercury. 

 This leads to a confusion with chlorate of mercury, then called by some 



