ANAtYSlS OF BRITISH AND FOREIGN SALT. \Q$ 



the pits is boiled for some hours in the pans, which are used 

 in summer to prepare co.niuoii salt; and the impuiities, 

 which rise to the surface, are removed by skimming. 

 During the evaporation, a portion of common salt separates; 

 and this, as it is too impure for use, is reserved for the pur- 

 pose of concentrating the briue in summer. Tin- evaporated 

 bitter liquor is then removed into wooden coolers 8 feet 

 long, 5 feet wide, and I foot deep. In these it remains 

 twenty-four hours, during which time, if the weather prove 

 clear and cold, the sulphate of magnesia, or Epsom salt, 

 crystallizes at the bottom of the coolers, in quantity equal 

 to about one eighth of the boiled liquor. The uncrystal- 

 lizable fluid is then let off through plugholes at the bottom 

 of the coolers; and the Epsom salt, after being drained in 

 baskets, is deposited in the store-house. This is termed 

 single Epsom salts ; and after solution, and a second crys- 

 tallization, it acquires the name of double Epsom salts. 

 Four or five tuns of sulphate of magnesia are produced 

 from a quantity of brine, which has yielded 100 tuns of 

 common, and 1 tun of cat salt. 



On the banks of the Mersey, near its junction with the ; Seawater satu= 

 Irish Channel, the water of that river before evaporation is salt 

 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 tuns of this 

 brine yield at least 23 tuns of common salt, whereas from 

 the same quantity of Seawater, with an equal expendi- 

 ture of fuel, only 2 tuns 17 cwt. of salt can be produced** 



Within the few past years, an attempt has been made to Rock salt use! 



r for provision- 



apply rock salt itself to the packing of provision. For this 



connected with the subject* I give his description of the mode at* 

 making Epsom salt, because no correct statement of the process has, t 

 believe, been hitherto published. The aualysis of sea«a:er, indeed, by 

 a justly distinguished chemist (Bergmau), excludes, erroneously, the Krrour of 

 sulphate of magnesia from its composition •, and his results have led Bergaiaa- 

 to the opinion, that, to manufacture this salt on the large scale, require* 

 the addition either of sulphuric afcidj or of some sulphate to the bitter 

 liquor. (See A ikin's Chemical Dictionary, II, 363.) ' - 



• See the Earl of Dundonald's " Thoughts on the- Manufacture and 

 Trade of Salt." London, 1785. 



O 2 purport* 



