1852 



Analysed for 

 iron. 



Mode of esti- 

 mating its 

 quantity. 



Pvoportions. 



Component 

 parts of alura. 



COMPARISON OP DIFFERENT KINDS OF ALUM. 



as it has generally been supposed, that this alkali would in- 

 jure the beauty of dyes» 



Exp, 5. The presence of iron in alums had been demon- 

 strated in a positive manner by several eminent chemists, who 

 considered them all, including the Roman, as one and the 

 same salt, except so far as its properties were altered by fo- 

 reign matters, and particularly by sulphate of iron. 



To ascertain its influence, it was necei^sary to know the 

 quantity contained in the alum: but analysis not affording, 

 any means of determining it with sufficient accuracy, Messrs, 

 Thenard and Roard had recouse to the synthetical plan. 

 Accordingly they took some alum perfectly free from iron, to 

 the solution of which they added from t^tt t<^ tAtj P^J't of 

 sulphate of iron ; and then ihey compared the effect of prus- 

 siate of potash on each of these solutions., more or less ferru- 

 ginous, with that it produced in solutions of the rive kinds 

 of alum. 



By this method they found, that the alum of Liege con- 

 tained at most T^otr of sulphate of iron, that of Javelle a 

 little less, that of Bouvier and of Curaudau riros ^^ tt'W* 

 and the Roman scarcely ^o-Vo* 



From all these experiments it follows, that the alums of 

 Rome, Bouvier, Liege, Javelle, and Curaudau contain pre- 

 cisely the same quantities of sulphuric acid, alumine, potash, 

 and water, and differ only by a few thousiindth parts of sul- 

 phate of iron: and that a hundred parts consist of 



Sulph uric acid Q6'04> 



Alumine • • 12*53 



Potash 10-02 



Water • 51*41 



, /- 



100 



Part IL 



- Experiments with Di/cs. 



r ' t After havins; given the results of their analyses in the first 



r^xpcrimcnts ° '^ '' 



with dyes. patr, Messrs. Thenard and Roard proceed to the second, 



which includes all their experiments with dyes. As this docs 



not 



