British and Foreign Salt. 1 1 1 



Tvish Channel, the water of that river before evaporation 

 is brought to the state of a saturated brine, by the addition 

 of rock salt. The advantage of this method of proceeding 

 will be obvious when it is stated, that 100 tons of this brine 

 yield at least 23 tons of common salt, whereas from the: 

 same quantity of sea water, with an equal expenditure of 

 fuel, only two tons 17 cwt. of salt can be produced *. 



Within the few past years, an attempt has been made to 

 apply rock salt itself to the packing of provisions. For 

 this purpose it is crushed to the proper size between iron 

 rollers. The trials which have been made, I am informed, 

 are but few, and the results hitherto are not perfectly 

 known. 



Thcbaysalt imported from foreign countries is well known 

 to be prepared bv the spontaneous evaporation of sea vva^ 

 ter, which, for this purpose, is confined in shallow pits, 

 and exposed to the full influer.ee of the sun and air. I 

 have no addition to make to the accounts of its manufac- 

 ture, which have already been given by various writers f. 



As the results of the investigation, which forms the sub- 

 ject of this memoir, may be acceptable to many persons 

 who can scarcely be expected to take an interest in a long 

 detail of analytical processes, I shall present, in the follow- 

 ing section, a general view of the experiments, and of the 

 conclusions that may be deduced from them. In the last 

 place, in order that other chemists may be enabled to re- 

 peat the analyses under similar circumstances, 1 shall de- 

 scribe minutely the methods that were adopted, some of 

 which are rrew, and others reduced to greater precision. 

 If, however, in the future progress of science, it should 

 appear that any of these processes are imperfect, it may 

 still be admitted that, for all useful purposes, they afford a 

 fair comparison of the composition of the several varieties 

 of culinary salt ; since the sources of fallacy, that may 

 hereafter be discovered, must have been the same in every 

 case, and have produced in each an error of nearly the 

 same amount. 



Sfxt. II. General Statement of the Results of the Experi- 

 ments, and Conclusions that may be deduced from them. 



A comparison of the component parts of British and 



* See the Earl of Dundonald'* * Thoughts on the Manufacture and Trade 

 of Salt." London, 1785. 



•y Encvclop. Method, art. Salins. (Des Marais Salans) Aikin's Dictionary 

 of Chemistry, ii. 224. Watson's Chemistry, vol. ii. p. 52. It is necessary 

 to rem;irk, that a great proportion of what is sold in London as hay-salt is 

 Cheshire large-grained tishery salt. foreign 



