ii THE ACIDS 25 



pared from Verdigris or Basic Acetate of Copper, 



Cu(C 2 H 3 0. 2 ) 2 + Cu(OH) 2 ; 



Acetate of Soda or Sodium Acetate, NaC 2 H 3 O 2 ; 

 Acetate of Lime or Calcium Acetate, Ca(C 2 H 3 O 2 ) 2 ; 

 Acetate of Magnesia, or Magnesium Acetate, Mg(C 2 H 3 O 2 ) 2 . 



Three systems of nomenclature are seen in the names given 

 to the salts set out above: (i) At first each salt received a 

 special name, in many cases recalling the origin or properties of 

 the salt. (2) The system of naming salts after the acid and 

 the metal, alkali or earth from which they are derived was 

 elaborated by de Morveau, Lavoisier, Bertholiet, and Fourcroy 

 in their Methode de Nomenclature Chimique, published in 

 1787. (3) This system became obsolete when Davy, twenty 

 years later, showed that the alkalis and earths contained 

 metals ; it was then possible to name every salt after the acid 

 and the metal from which it was derived and to abandon the 

 use of the alkalis and earths in naming salts. 



The idea that salts still contained the acid and alkali from which 

 they were derived was put forward by John Mayow in his Medico- 

 Physical Works published in 1674 ; he showed that Ammonia 

 could be displaced from its Salts by Potash, 2NH 4 C1 + K 2 CO 3 

 ->2KC1 + (NH 4 ) 2 CO 3 and Aqua Fortis by Oil of Vitriol, 

 2KNO 3 + H 2 SO 4 -> K 2 SO 4 + 2HNO 3 , and was impressed with 

 the idea of the unequal " concordance " of the two acids with 

 the alkali, an idea that is essentially the same as that of the 

 unequal strengths of different acids. Rouelle, to whom we owe 

 the terms base (Mem. Acad., 1754, 572) and water of crystalli- 

 sation (ibid., 1744, 356) described how neutral salts had been 

 restricted at first to " salts formed by the union of acids with 

 alkalis, which are soluble in water, and imprint on the tongue 

 a saline taste. . . . The number of neutral salts was at first 

 very small, scarcely any were known but sea salt and nitre ; but 

 the number was soon increased, above all by the work of 

 Glauber. Others have since been added of which the bases are 

 the volatile alkali and an absorbent earth. Finally there have 

 been added salts formed by the union of acids with metallic 

 substances" (Mem. Acad., 1754, 572). He himself, in 1744, had 

 defined as a neutral salt, " a salt formed by the union of an acid 

 with any substance whatever, which serves as a base for it and 

 imparts to it a concrete or solid form " (ibid., 573). 



