ANALYSIS OF BRITISH AND FOREIGN SALT. OQg 



The proportion of ingredients in the several kinds of mtt- Proportions of 

 riateof soda (setting apart the impurities) appears, there- |^^ s ; x- 

 fore, to be nearly the same in all. And as the very minute cepted, nearly 

 quantity of water, discovered by analysis, is not constant thesaraemaU * 

 in the several varieties, it may be inferred to be rather an 

 accidental than a necessary ingredient ; for in the latter case 

 an invariable proportion might be expected, conformably to 

 •the important law, establishing a uniformity in the pro- 

 portions of chemical compounds, which has been explained 

 by Mr. Dal ton, and confirmed by Drs. Thomson and Wol- "3 



last on. 



What then, it may be inquired, is the cause of those dif- What is the 

 ferences, which are acknowledged, on all hands, to exist d * fference of 

 among the several species of muriate of soda, so far as re- quality in salt? 

 spects their fitness for economical purposes? If I were to 

 hazard an opinion, on a subject about which there must 

 •till be some uncertainty, it would be, that the differences Nottheche- 

 of chemical composition, discovered by the preceding train n«cal composv 

 of experiments, in the several varieties of culinary salt, are 

 scarcely sufficient to account for those properties, which are 

 imputed to them on the ground of experience. The stoved 

 arid fishery salt, for example, though differing in a very tri- 

 vial degree as to the kind or proportion of their ingredients, 

 are adapted to widely different uses. Thus the large grained 

 salt is peculiarly fitted for the packing of fish and other 

 provision, a purpose to which the small grained salts are 

 much less suitable. Their different powers then of pre- but the size of 

 serving food must d pend on some mechanical property ; rystaIs ' 

 and the only obvious one is the magnitude of the crystals, 

 and their degree of compactness and hardness. Quickness 

 of solution, it is well known, is pretty nearly proportional, 

 all other circumstances being equal, to the quantity of sur- 

 face exposed. And since the surfaces of cubes are as the 

 squares of their sides, it should follow, that a salt, the cry- 

 stals of which are of a given magnitude, will dissolve four 

 times more slowly than one, the cubes of which have only 

 half the size. 



That kind of salt then which possesses most eminently Practical appfi- 

 the combined properties of hardness, compactness, and per- callou » 

 faction of crystals, will be best adapted to the purpose of 



packing 



