ii8 Ohfcrvatlons upcn the art of 



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by boiling, and fet by to cool, fait will be produced hi th 

 form of fine delicate needle point cryilals ; having, when 

 taken ont of the liquid, the appeara^ice of iriow. This is no 

 -ftther than the genuine bitter cathartic fait of Epfom, fo called 

 from the mineral fprin^ of Epfbm, where it was originally dif- 

 covered by Dr. Grew, Although this and the glauber fait are 

 in their chymical properties efTentlally diflimilar, they are ia 



medicinal virtues nearly allied, aiid often prefcribed indiicrim- 

 inately. Another article in the preparation of which fome 

 attenapts have been made at the works on the Cape, is mag- 

 iiefia alba. The fpeclmeris of it, which I have infpe(fled, arc 

 manifeftly inferior to Englilh magnefia. "That prepared 



directly from, the bittern, is by no Tri£aas_equ?d in purity to 



that prod.\iced from 



Our workmen are confefTedly unacquainted with the mofl 

 eligible method of obtaining it in genuine purity ; nor can 

 they have accurate ideas upon the fubjecfl:, unlels they pofTefs 

 fome knowledge of tlie laws of chymical affinity, and the 

 'powers of eledlive attracllon. Incidents influenced by thefc 

 principles, although perfetflly familiar to the mind of every 

 chymical operator, would be coniidered by thofe not verfed 



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in that fcience, '^s' inexplicable phenomena. Referring to 



' chymical writers for further information, it will fuiEce for our 



purpofe to obferve, that an acid and alkali poffefs oppofite 



principles, and that a combination of the two, form a neutral 



compound, Epfom fait is precifely in this predicament, being 



formed 



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