t5$ IrORKSHIRE ALUM WORKS. 



Exp. 3. The remaining solution of tlie 2cl experiment, 

 after boilinj^ quicklime in it to take the arid from the amino-' 

 uia, was evaporated to dryness, and afterward exposed to 

 a red heat. The potash, or soda, thus produced, weighed 

 858 grains. 



I repeated the analysis twice, the results, after taking 

 every precaution, are as under: 



1st Exp. 2d Exp. Mean ot the two. 



Sulphuric acid .^ 33*59 •••• 33*10 "^ 33*34 



Aiumine 10'96 •••• 11-81 ( 11-33 



Soda or potash 8*58 •••• 974 C 9' 16 



Water ...- 46-87 45-35 J 46-12 



100 100 100. 



In finding the quantity of water contained in crystaUized 

 alum, by exposure to a red heat, an uncertain product will 

 always be given, arising from the degree of heat employed 

 in the desiccation of the alum. At a white heat a very con- 

 siderable proportion of acid will be expelled, as well as the 

 water. 



In the production of alkali from the alum, I have called, 

 it soda, or potash. I did not institute any experiments to 

 ascertain the quality of the alkali, but as nothing but kelp 

 and black ashes had been used in the fabrication of the 

 alum, it is evident the alkali must have been soda with per- 

 haps a small proportion of potash. So that in reality we 

 have a lifth variety in addition to the four described by Dr, 

 Thomson. 



It remains then of some importance to the consumer to 

 ascertain the difference between alum made with potash, and 

 that in which a salt of soda is used, 



I have received considerable advantage from the very able 

 memoir of Messrs. Thenard and Roard, as inserted in your 

 Journal, vol. 18, p"age 276. 



Had these philosophers adopted 33 per cent of acid in 

 the sulphate of barytes, instead of 26, as is stated in their 

 paper, our results would not have been very different. By 

 correcting their statement of the composition of alum, ac- 

 cording 



