CHEMICAL EFFECTS OF PUDDLING. 125 



phur in the state of sulphuretted hydrogen failed, owing to 

 the difficulty of removing the last traces of sulphuretted 

 hydrogen held in solution in the liquid in which the iron is 

 dissolved and in which the gas is produced. As to the 

 process which consists in dissolving the iron in aqua regia 

 and boiling off the greatest part of the acid and then adding 

 nitrate of baryta to the solution, it cannot be followed with 

 security, for one of us has shown that sulphate of baryta is 

 soluble in acid liquors, especially in those containing nitric 

 acid, and often in such quantities as to make a greater dif- 

 ference between the analyses of two samples of the same iron 



the real difference which exists in two samples of iron 

 from different ores. 



These considerations induced us to modify the last men- 



l process in the following way. Five grammes of the 

 sample of iron to be analysed were reduced to fine powder 

 and gradually and slowly added to a strongly oxydizing aqua 

 regia, composed of four parts of fuming nitric acid and one 

 part of hydrochloric acid. The iron being dissolved, the 

 solution was evaporated to the consistence of a thin syrup, 

 and then gradually mixed with four times its weight of a 

 mixture of pure carbonates of potash and soda, and heated 

 to redness for one hour in a platinum crucible. The fused 

 mass was then heated with boiling water until all the soluble 

 portion was dissolved. This liquor was then rendered slightly 

 acid with hydrochloric acid, evaporated to dryness, and heated 

 at 200° C, to render the silica insoluble. The whole was 

 then heated by water slightly acidulated with acetic acid, 

 and on the silica being separated by filtration, the amount 

 of sulphate, and consequently, of sulphur, was determined, 

 from the weight of sulphate of baryta obtained. 



Phosphorus. 



We also attached great importance to the exact valuation of 

 tin- body, because, like sulphur, its presence even in small 



