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An Analysis of several Varieties of British and Foreign Salt (Muriate 

 of Soda), with a view to explain their Fitness for different economical 

 Purposes. By William Henry, M.D. F.R.S., Vice-Pres. of the 

 Literary and Philosophical Society , and Physician to the Infirmary , at 

 Manchester. Read January 25, 1810. [Phil. Trans. 1810,^. 89.] 



An opinion having for some time prevailed, both in this and in 

 other countries, to the prejudice of British salt as a preserver of ani- 

 mal food, and large sums of money being annually paid to foreign 

 nations, in conformity to this opinion, for the supply of an article 

 which Great Britain possesses beyond almost any other country in 

 Europe, Dr. Henry has been induced to undertake the present in- 

 quiry, for the purpose of ascertaining whether the preference of foreign 

 salt be founded on accurate experiments, or merely a matter of pre- 

 judice ; and in the former case, whether any chemical difference 

 could be discovered that would explain that superiority. 



The subject is divided into three parts : in the first of which are 

 contained, general observations on the different kinds of salt manu- 

 factured, and the modes of preparing them. The second division 

 contains the general statement of the results of the experiments, and 

 conclusions deducible from them. But since a long detail of analy- 

 tical processes must be uninteresting to very many persons, to whom 

 the results will be acceptable, the description of the method em- 

 ployed by Dr. Henry, in his analysis, is reserved for the last section, 

 in which (as the author observes) are not to be expected any novel- 

 ties in science, but merely a careful selection and employment of 

 known processes. 



The principal sources of the salt manufactured in this country are : 

 the rock salt of Cheshire ; the brine springs, which are also mostly 

 in the same district ; and sea water, which cannot be evaporated ar- 

 tificially with profit, excepting where fuel is cheap. 



Concerning the preparation of salt in Cheshire, Dr. Henry extracts 

 a brief statement from an excellent history given by Mr. Henry Hol- 

 land, in the agricultural report of the county of Chester; and he no- 

 tices four varieties. 



First. That which is called stoved or lump salt. Second. Called 

 common salt. Third. Large-grained flaky salt. Fourth. Fishery salt ; 

 the difference among these depending principally on the degree of 

 heat used for evaporation of the brine. 



The stoved salt is prepared by rapid evaporation at a boiling heat 

 of 226 Fahrenheit, and it obtains its name from being subsequently 

 dried in stoves after being well drained. 



For making common salt, the brine is evaporated at a temperature 

 between 160 and 170; and as the salt is consequently formed in 

 somewhat larger grains, it is merely drained, and does not require to 

 be dried in stoves as the former. The name of the third, or large- 

 grained flaky salt, implies a slower process of crystallization, and it 

 is conducted at a temperature of 130 or 140 degrees. 



The last, or fishery salt, which is the largest, is prepared at a heat 



