British and Foreign Salt. 1 1 7 



differences which are acknowledged, on all hands, to exist 

 among the several species of muriate of soda, so far as re- 

 spects their fitness for (economical purposes ? If I were to 

 hazard an opinion, on a subject about which there must 

 still be some uncertainty, it would be that the differences 

 of chemical composition, discovered by the preceding train 

 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 and fishery salt, for example, though differing in a 

 very trivial 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 provisions, a purpose to which the small- 

 grained salts are much less suitable. Their differenl powers, 

 then, of preserving food must depend on some mechanical 

 property; 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 surface exposed. And since the -surfaces of 

 cubes are as the squares of their sides, it should follow that 

 a salt whose crystals are of a given magnitude will dissolve 

 four times more slowly than one whose cube3 have only 

 half the size. 



That kind of salt, then, which possesses most eminently 

 the combined properties of hardness, compactness, and 

 perfection of crystals, will be best adapted to the purpose 

 of packing fish and other provisions, because it will remain 

 permanently between the different layers, or will be very 

 gradually dissolved by the fluids that exude from the pro- 

 visions; thus furnishing a slow but constant supply of 

 saturated brine. On the other hand, for tiie purpose of 

 preparing the pickle, or of striking the meat, which is done 

 by immersion in a saturated solution of salt, the smaller- 

 grained varieties answer equally well; or, on account of 

 their greater solubility, even better. 



With the hardness or strong aggregation of the several 

 varieties of salt, it seemed to me not improbable that their 

 specific gravity might in some degree be connected. The 

 exact determination of this property in saline substances is, 

 however, a problem of considerable difficulty, as will suffi- 

 ciently appear from the various results which have been 

 given, with respect to the same salts, by different experi- 

 mentalists. Thus Muschenbroek makes the specific gra- 

 vity of artificial muriate of soda to vary from 1918 to 2148, 



H 3 the 



