278 VEGETABLE SUBSTANCES. 



boiled in iron vessels, and the residuum is converted 

 by calcination into an alkali*. 



The proportion of pure alkali contained in potash 

 varies extremely. Four parts by weight of the best 

 American potash should contain about three parts 

 of pure alkali ; some inferior kinds yield only two 

 parts, the rest is made up of earthy matter and other 

 salts. Mr. Dossie ascertained on analyzing potash 

 of different qualities, that the proportion of earthy 

 matter was always nearly the same, and that the 

 specimens varied with respect to the admixture of 

 other salts. Thus one pound of the best potash was 

 found to consist 



oz. 



Of pure alkali 12-5 



Other salts -9 



Earthy matter 2-6 



16 



While another pound contained 



Of pure alkali only . ,/.,.,..'' 8'3 

 Other salts . . . . . ... . j 5'4 



Earthy matter 2-3 



16 



In one hundred parts of Dantzic pearlash the 

 pure alkali amounted to somewhat above sixty-three. 

 It is therefore not as strong as the best American 

 potash. 



In 1831 England imported from Canada for home 

 consumption about 167,000 cwt., and from other 

 parts 25,000 cwt. of pot and pearl-ashes. They are 

 admitted duty free from British possessions; coming 

 from foreign countries a duty of 6s. per cwt. is levied. 

 The price of Canada potash is from 1. Us. 6d. to 

 l, 15s. per cwt. ; that of St. Petersburgh, with the 

 * Macquer's Chemical Dictionary, article Alkali, 



