I RAW MATERIALS AND PRIMITIVE MANUFACTURES 3 



their solubility in water, and contained a large proportion of 

 the substance now known as COMMON SALT (Fig. i). The 

 name SALT was applied subsequently to all similar solids. 

 Thus Boyle denned a " salt " as being characterised by two 

 qualities, that " it is easily dissoluble in water and that it 

 affects the palate with a savour, whether good or evil " (see 

 Experiments and Notes about the Produdbleness of Chymical 

 Principles, 1680, p. 3; Works, 1725, III. 365). 



SODA (Latin natruni), known from the earliest times as a 

 natural deposit on the shores of the soda-lakes of Egypt, 

 was originally 

 called " nitre "; 

 it was employed 

 as a cleansing 

 agent and in the 

 manufacture of 

 glass, but was 

 almost u n - 

 known in West- 

 e r n Eu rope 

 until the eight- 

 eenth century, 

 when it was 

 prepared from 

 the ash of marine plants. POTASH, or " pearl ash," a 

 white solid closely resembling soda in many of its pro- 

 perties, probably received its name from the fact that it 

 was obtained by extracting the white ash of burnt wood 

 with water in earthenware pots. During the middle ages 

 the chief source of potash was the "lees" or sediment 

 of wine to which the name of TARTAR was given ; this 

 sediment was calcined, and the potash thus prepared, the 

 " burnt lees of wine," was known as CALCINED TARTAR, or 

 more simply as " tartar." These two substances, soda and 

 potash, were known as ALKALIS, and were remarkable for 



B 2 



FIG. T CUBIC CRYSTAL OF SALT. 

 British Museum (Natural History). 



