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XXXVIII. Chemical Olservations upon Spathic Iron. Bj 

 M. Collet Descostils, Engineer of Mines. Read at 

 the Class of the Sciences in the Frenclt, National Institute, 

 January 6, 1 806 *. 



A think there is no mineral substance the various analyses 

 of which present so niany important differences as those of 

 Spathic iron, and the treatment of which, in some forges, • 

 agrees also so ill with the opinion given of its composition 

 in the most of these analyses. After having examined the 

 processes employed by the chemists who have published 

 them, and having niade some experiments upon the same 

 subject, I think I have discovered the cause of the dif- 

 ferent results which they announced, or the errors which 

 they committed. I shall explain in this memoir the results 

 of my labours, and I shall conclude it by some conjectures 

 upon the causes of several metallurgical practices made use 

 of in the treatment of spathic iron, and which I think have 

 not been hitherto satisfactorily explained. 



Bayen, I presume, was the first chemist who analysed 

 spathic iron. His work, which appeared to me to contain 

 some errors, presents, however, some unquestionable re- 

 sults which seem to have been forgotten, and which I think 

 I ought to bring to recollection. 



Distillation and the action of the acids convinced 

 M. Bayen, 1st, That this ore contains a gas of the nature 

 of fixed air, to which he attributes the property of crystal- 

 lizing the iron. 2d, That it contains fragments of quartz, 

 which remain in the liquor after its complete solution, if it 

 has been exposed in small portions to the action of the acids. 



The crystallization of some sulphuric solutions, without, 

 excess of acid, sometimes presented small quantities of sul- 

 phate of lime, at other times he did not perceive an atom 

 of it ; and he concluded from this, that the above ore, con- 

 sidered in the mass, is found in some places mixed with cal- 

 careous spar. 



The other experiments he relates, and the consequences he 



* From Jjurnal da Minn, vol. xviii. 



Cj 3 • deduces 



