90 Professor Fuchs on a new Method of analysing 



it in a retort until vapours of sulphuric acid pass over, where- 

 by there is at the same time the advantage of having an acid 

 of r85 sp. gr. 



In the distillation of sulphuric acid several precautions have 

 been proposed to avoid the sudden jerks {stossweise) in the boil- 

 ing of the acid, yet most of them are by cautious equal heat- 

 ing, even the platina wire, unnecessary, and I have at last even 

 distilled without this over an open fire, without ever meeting 

 with an accident. But it is very necessary that the neck of the 

 retort is not too long and is as broad as possible, and that the 

 receiver does not lie immediately on the neck of the retort, 

 but is separated from it by a platina wire, and that an equal 

 fire be kept up, which is best attained by using charcoal. The 

 retort is filled two-thirds with sulphuric acid, placed with the 

 usual precautions in the sand bath, and at first a good fire 

 kept up until strong vapours ascend from the acid ; the fire 

 is then diminished, and the acid comes to boil gently. Care 

 should be taken, by keeping up an equal fire, that the acid 

 does not cease boiling; should this happen, it is not necessary 

 to interrupt the distillation, but the fire must be cautiously in- 

 creased, that the acid may not enter suddenly into a too vio- 

 lent ebullition. 



XVI. A neia Method of analysing the Ores of Iron, and Crude 

 Iron. By Prcfessor Fuchs*. 



THIS process is founded upon the fact, that hydrochloric 

 acid is incapable of dissolving metallic copper, provided the 

 air be excluded ; but if a piece of copper be put into a solu- 

 tion of a persalt of iron in hydrochloric acid, the persalt is 

 converted into a protosalt,and a quantity of copper is dissolved, 

 forming a protosalt of copper exactly equivalent to the quan- 

 tity of peroxide of iron contained in the solution. 



Into a solution of peroxide of iron in hydrochloric acid put 

 a piece of copper, whose weight is accurately known ; boil it 

 well until no more copper is dissolved ; weigh the undissolved 

 copper after having cleaned and dried it, and thus ascertain 

 how much copper has been dissolved. The quantity of per- 

 oxide of iron contained in the solution is to that of the cop- 

 per dissolved as their respective equivalents, viz. as 40 to STT. 

 Therefore if 31*7 copper be dissolved, it indicates 40 as the 

 quantity of peroxide of iron originally contained in solution. 



When the peroxide and protoxide are both present, two 

 experiments are necessary to determine their respective quan- 



* Extracted from the Transactions of the Royal Bavarian Academy. 



I 



