ON THE OXIDES OF IROIT* ^71 



eludes, that 100 parts of iron w>ould take up 37*29 of oxigen 

 in this exeriment. 



The result here depends on too many circumstances, jto Objections, 

 make known the proportion of iron contained in the oxide or 

 oxidule. In fact the quantity of precipitate compared with 

 the iron dissolved depends, Ist, on the quantity of oxigen 

 combined with the silver in the solution ; 2dly, on the pro- 

 portion of silver precipitated from nitric acid by mercury; 

 3dly, on the quantity of oxigen which mercury takes up on 

 being dissolved in nitric acid : and if these three data be liOt 

 strictly accurate, the final result cannot be determined with 

 precision. Proust says he has discovered, that silver may be Two nitrates 

 oxided either at a maximum or a minimum in nitrate of sil- o* silver, 

 ver* ; and hence we have a fresh source of errour in the in- 

 ference of Lavoisier. 



Bucholz attempted to determine the proportion of oxigen Bucholz form- 

 in the oxidule of iron, by suppoainff that in the oxide to be ?^ ^^! p^otox- 

 . / "^ * ^ *> ide of iron by 



known. With this view he passed the vapour of water over means of heat 



red hot iron, and obtained an oxide, which on trituration ^"^ ^'^^^^' 



furnished a black powder. This, being subjected to the 



action of muriatic acid, and to several other tests, w as found 



to be an oxidule of iron. 



This oxidule was dissolved in nitric acid in tlie same man- and converted 



ner as iron, the fluid evaporated, and the residum kept at a !\ ^"^^ perox- 



11 *. r. 1 I • 1 1 • 1 ide by nunc 



red neat tor a quarter or an hour, when it had gained an ^cid. 



addition of one tenth to its weight. This, on the supposi- 

 tion that the red oxide contains 42 of oxigen to 100 of iron, 

 would give SOfof oxigen to 100 of iron for the oxidule; and Calculations 

 on the supposition of the red oxide containing 44, the oxi- '^®''° '"'^ 

 dule would contain 31 to 100 parts of metal ; and 100 of ox- 

 ide [oxidule] would be composed of 7(>-3 iron, and 23*7 oxi- 

 gen, which agrees with the resultsof Lavoisier and Bucholz. 



6th methot^. 0/ the quaniity of oxigen determined by the 

 decomposition of nitre, 



Guyton projected equal parts of iron filings and nitre into ircncxtdedVy 



a red hot crucible, washed the residuum repeatedly in boil- "^"'^' ^-^ ^"-'^ 



• ton 



ing water, and obtained an oxide, in which the iron had re- ' 



ceived an addition of 34 parts to 100, 



♦ Journal de Phvs 1799, vol TT,p £21. 

 t 2d I onW. C 



Laroisier 



