254 YORKSHIKE ALUM WORKS. 



manufactory. It contains about 47 of soluble salts, and 53 

 of charcoal, sand, and earth. The salts are muriate of sodaj 

 soda, and sulphate of soda. 



The refuse of the soap boilers' lees are burnt in a kind of 

 oven, and sold under tlie name of black ashes. The compo- 

 sition of these ashes is about 90 of soluble salts, and 10 of 

 charcoal and earth, the salts contain muriates of soda 

 and potash, sulphate of potash, and muriates of lime and 

 magnesia. 



I have always found great difficulty in producing alum 

 by the muriate of soda, and never could form alum in any 

 way by means of pure soda. 



The muriate and sulphate of potash are the only alkalis 

 that can be used to advantage in the composition of alum. 



I have made comparative experiments to ascertain the 

 quantity of the different alkalis it would require to produce 

 100 tuns of alum. The following are the results: 



22 tuns of muriate of potash will produce 100 tuns of alum, 



"^ 31 ditto of black ashes 100 ditto, 



73 ditto of kelp 100 ditto. 



The alkalis are considered as in tlie state, in which they 

 are found in commerce. 



Analysis of sulphate of alumine, and svpersulphate of alu' 

 mine and potash. 



Analysis of sul- I have been generally disappointed in analyzing alum on 



pkateofala- fi^^(]inff rav results at variance with those of so many emi- 

 mine, ^ . _ , , , . , . 



nent chemists. It appears, that the errour has existed in 



their different estimations of the composition of sulphate of 



barytes. It seems, that allowing about 33 per cent of acid 



is very near the truth*. By taking it in this ratio, the acid 



* According to some very careful experiments made by Mr. Arthur 

 Aikin, see Journal, vol. XXII, p. 30t, it is nearer 34. He makes it 

 33 96 ; and according to Klaproth it is S3*65. See also an Analysis by 

 Mr. James Thomson, vol. XXllI, 174; and another by Berthier, ib, 

 p. 280 : both of whom make it at least S3. C. 



used. 



