34 Common Salt. [Book VI. 



but never in confiderable quantities ; it is found in fea- 

 water, and in the water of fait fprings, and it exifts, 

 thoueh rarely, in places where nitre is founds it is 

 likewife met wkh in the afhes of vegetables, and in 

 animal fluids. It is not employed in the arts, and its 

 bitter tafte prevents its being ufed for culinary pur- 

 pofes. In moft of its properties, however, it is very 

 fimilar to common fait. 



id. COMMON or MARINE SALT is compofed of the 

 muriatic acid and the mineral fixed alkali, and is there- 

 fore the muriat- ofjbda of the new nomenclature. This 

 fait requires a full red heat for its flifion ; foon after 

 this it begins to evaporate in white fumes. It has a 

 flrong attraction for water, fo as to deliquefce in a 

 moift air. During evaporation, the cryftals of this 

 fait form at the top of the folution, contrary to thofe 

 of other falts, which form at the bottom. When the 

 evaporation is carried on quickly, it forms into thin 

 irregular crufts, and this is the ftate in which we com- 

 monly have it. When the evaporation is flow, it 

 affumes the cubic form, and the fmalleft cryftals are 

 the mod regular ; but if examined accurately, one of 

 their fides will be found a little hollor/. The larger 

 cryftals have a pyramidal hollow apex, with a broad 

 bafe. This is owing to their fuperior furfaces being 

 dry when floating in the water, while their inferior 

 furfaces are moiftened. Hence, as all dry bodies have 

 a repulfion for water, and as their inferior furfaces have 

 a tendency to fink, they are hollowed into little pits 

 on the fuperior furfaces. 



This fait contains little water of cryftallization-, and 

 decrepitates in the fire. If frequently diffolved, evapo- 

 rated, and dried, its quantity is more diminifhed than 

 4hat of any other fait. By decompofition we obtain 

 'either its acid or 'its alkali. The old chemifts ufed to. 

 i obtain 



