^yQ ON THE OXIDES OF I! 



same precautions, and employed the same care in their ex- ^ 



periments, wewill leave itfor the present undecided, whether 



100 of iron be mixed with 42 or 44 of oxigen in the red 



oxide. 



The oxide pre- 2nd Method, Guyton dissolved iron in nitric acid, and 



cipitated by precipitated it v^ith salt of tartar. The precipitate, after 

 an alkali, by , . ,, , , i i • i i i • i 



t5uyton, being repeatedly washed and dried, had increased 32'1 on 



100 of iron. 



and Lavoisier. Lavoisier precipitated the nitric solution of iron by cauf»- 

 " 'tic alkali, and obtained two different precipitates. 1st, 

 When the solution was weak, made without heat, and pre- 

 cipitated by pure caustic ammonia, this illhRtrious chemist 

 had a black precipitate, in which the weight of oxigen to 

 100 of iron was 30. 2dly, When the acid was concentrated, 

 and the solution promoted by heat, the iron received an in- 

 crease of 40 or 50 per cent, whatever were the acid em* 

 ployed; and this precipitate, after being calcined, retained 

 only 25 or 30 parts of oxigen to the 100 of iron. 



Oxide of iron in sulphuric acid diluted with water, when 

 precipitated from its solution, and afterward dried in close 

 vessels, Lavoisier found to be in the state of ethiops, and 

 containing from 25 to 30 parts of oxigen to 100 of metal. 



Probable This great diminution of the weight of the precipitated 



courceof er* oxides obtained by Lavoisier miofht lead us to suppose, that 

 rour in Lavoj- -^ *. . . 



sier's exp. some coally substances had got into the vessel containing 



the oxide, and contributed to the reduction of part of the 

 oxide to the metallic state. 

 These expe»i- ^^ ^^ difficult to draw accurate conclusions from these ex- 

 nientsincon- periments, because it is not certain, whether, by virtue of 

 that chemical action of which Berthollet has proved the ex- 

 istence, a portion of the alkali had not been carried down by 

 the precipitate, and a portion of the oxide retained hy the 

 menstruum. In fact Fourcroy found, that the oxides of 

 iron precipitated by ammonia retained a portion of the pre- 

 cipitant. 

 Soluiio» of 3d Method. Bergman remarked, that 20 parts of steel 



silvor precipi- ©f Osterby tlirew down 66 parts of silver dissolved in sulphu- 

 tated by iron , .,, f-ni ,-., ,i 



by Bergman, "C acid ; whence it toliows, that 100 parts of silver would 



have been precipitated by 29 iron. From this Lavoisier con- 

 cludes. 



