34 Analysis of Iron Ore. 



tained ever so little lime*, sulphate of lime would have 

 been infallibly precipitated, particularly after cooling, be- 

 cause the water in the solution was but little; and that there 

 might not be an excess of acid, I had the precaution not to 

 add any new sulphuric acid before that previously poured in 

 had entered into combination : besides, in a preliminary 

 trial which I made by means of the muriatic acid, I obtained 

 no precipitate by the oxalate of ammonia. 



(B) In order to separate the oxide of manganese which I 

 supposed to be contained in the spathic iron, I thought the 

 following process the most proper : 



I diluted with distilled water five grammes of the same 

 substance. I poured nitric acid on it by little and little, 

 with the same precautions as above detailed. The solution 

 took place very rapidly ; the same phaenomena were again 

 produced, but with a disengagement of nitrous vapours. 

 The solution was afterwards decanted into a porcelain cup, 

 evaporated to dryness, and diluted in a new quantity of 

 water. I repeated these operations twice successively, be- 

 cause I had remarked that once was not sufficient, the oxide 

 of iron remaining suspended in the liquor and passing through 

 all the filters. I would even advise those who wish to re- 

 peat these processes, previously to imbibe the filtering paper 

 with a little distilled water ; the oxide of iron will not then 

 pass through so easily, and will also be more easily sepa- 

 rated. If it should happen that the oxide is so much in- 

 crusted that it is not possible to detach it without a great 

 Joss, the best course to follow would be to incinerate the 

 filter in a crucible of silver or platina. By following this 

 method I extracted the following quantities of the red oxide 

 of iron: from No. I. 3*05 grammes; from No. II. 2*45; 

 from No. III. 2*45 grammes. 



(C) The liquors which had passed through the filters 



4 More than a year ago, I had occasion to analyse, in the laboratory of the 

 Council of Mines, a specimen of white ore of iron, which was sent to me by 

 M. Lenoir, engineer of the mines. This specimen, which had the appear- 

 ance of some of the stones for building (limestones), found in the neighbour- 

 hood of Paris, did not yield a single atom of lime. 



were 



