|g| ANALYSIS OF BRITISH AND FOREIGN SALT. 



packing fish and other provision; because it will remain 

 permanently between the different layers, or will be very 

 gradually dissolved by the fluids, that exude from the pro- 

 vision; thus furnishing a slow, but constant supply of satu- 

 rated brine. On the other hand, for the purpose of pre- 

 paring 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. 



Specific gravi. With the hardness or strong aggregation of the several 



P" 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 gravity 

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

 mean of which is 2033. Sir Isaac Newton states it at 2143, 

 and Hassenfratz at 2200*. All (hat was necessary for my 

 purpose was an approximation to the truth ; and the intro- 

 duction of a small errour could be of no importance, pro? 

 vided it were the same in every case, since the comparison 

 would still hold good. 



{Loci salt, ^ le s pe c ifi c gravity of rock salt there can, be little diffi r 



culty in determining with precision. A piece of this salt*, 

 of such perfect transparency, that I had reserved it as a 

 cabinet specimen, weighed in the air 513 grains, and lost, 

 when weighed in alcohol, 194 grains. The alcohol, at the 

 temperature of 56° Fahrenheit, had the specific gravity of 

 820, and hence that of the salt may be estimated at 2170. 

 Another specimen considerably less pure, and more ap- 

 proaching to a fibrous fracture^ had the specific gravity of 

 2 1 25 only. 



Modeofascer- For ascertaining the specific gravities of artificial varieties 



Uiningi espc- ^ sa j ts \ usec i a verv simple contrivance. It consisted of a 



anc gravity or r 



different kinds <r\ass globe about 3^ inches diameter, having a stem or 



«£sah. 



• Anr.aVs de Chimie, vol. XXVIII, p. 13. 



f Foliated rock salt of Jameson. Sec his Mineralogy, vol. I J, p. 10. 



neck 



