t\o On the Component Parts oflron-Jttinii* 



fulibility of the mixtures, for a determinate fpace of time 

 The argillaceous iron-ftonc would be found in a given time 

 to have gained leaft ; the calcareous a larger portion ; while 

 the iiliceous, containing an affemblage of mixture fufible at 

 a decree of heat in which the former would remain un- 

 changed, will be found to have gained the greateft weight ', 

 but if expofed to an high temperature for a fufficient length 

 of time, the oxygen abforbed will be in an exael proportion 

 to the iron contained in the Hone ; only, the filiceous iron- 

 Hones arrive fooneft at a high pitch of combination. In the 

 courfe of many experiments I have found the following pro- 

 portions to be nearly juft, when the quantity of iron con- 

 tained in the refpecVive {tones was nearly analogous. 



Argillaceous iron-ftone, which has yielded me 38 percent, 

 in the afTay- furnace, firft diftilled and afterwards carefully 

 de-oxygenated, increafed in weight, during an expofure to 

 ignited gas for 8 hours in the bottom of a deep crucible, 

 23 per cent. 



Calcareous iron-ftone, which afforded a fimilar quantity 

 of metal, and which was fubjected to the fame train of pre- 

 paration, to difpel its volatile mixtures, and unfix its oxygen, 

 gained in weight nearly 23 per cent. 



Siliceous iron-ftones, containing from 36 to 38 parts of 

 iron in 100, treated lit the fame manner, afforded me inftan- 

 ces of an accumulation of weight equal to 24 to 25 per cent. 



In order more particularly to illuftrate the double pheno- 

 menon of iron-ftones firft lofing and then gaining weight, 

 I (hall infert the treatment of one particular (tone of each 

 clal's; from which a pofitive judgment maybe formed of the 

 general operation, and remits, peculiar io each. 



1. There were introduced into an iron teft fome pieces 

 of argillaceous iron-ftones, weighing - - i75ogrs. 



After being expofed to a bright red heat for 8 

 hours, and then allowed to cool, they weighed 1160 



Loft in fimple diftillation - - 590 grs. 



Equal to 33-6 per cent. Specific gravity in this 



ftate 2,52150. 



The 



