354: ON THE OXIDES OF IRON. 



A. Experiments to determine the Quantify of Oxigen in, 

 Red Oxide of Iron, 

 Sicd oxide 1. On a hundred grains of the iron aboyemeutioned, in 



the state of filings, an ounce of water was poured ; and 



nitric add at 1*^63 was added gradually, till the iron was 



entirely dissolved. 

 co-nta'im 295 The liquid being cautiously evaporated, and the matter 

 of oxigen, having remained at a red heat for a quarter of an hour, its 



weight was. increased forty two grains. This result differs 



from those of Lavoisier and Proust. 



■2. The same experiment repeated with this difference, 



that sometimes half an ounce of nitric acid, at others an 



ouKce and half were employed, the results were the same. 



B. Experiments on the Blade Oxide of Iron, 

 Ekck oxide. Mr. Bucholz made many attempts to obtain the black 



oxide. He tried calcination, the action of cold water on 

 iron filings, and the precipitation of green muriate of iron 

 Ammomaand hy ammonia and by potash*. Though these alkalis, says 

 potash precipi- jyjj,^ Buchoiz, did not produce me pure black oxide, their 

 tate mufiate of , . ,. . . , . -. . 



iron, addition in small quantities to the muriate of iron taught 



me, that the first precipitate of a greenish white, and the 



second of a blueish green, consisted of black oxide of iron 



only retaining more or less muriatic acid ; whence it fol- 



not free from lows, that these precipitates are not to be considered as dis- 



^'^^'^- tinct oxides; 



Aqueous va- Water in the state of vapour being made to pass through 

 pour converts Jj-qh filings heated red hot, a black powder was obtained, 

 into black *^ possessing all the characters of an oxide of iron at a mini- 

 oxide jxjum. 



A hundred grains of this black oxide were boiled with 



six ounces of nitric acid at 1-265. The solution was com- 



plete. Being evaporated and strongly calcined in a cruci- 



containing0 23 ble, a red powder remained, weighing 110 grains. The 



ot oxigeu. j^j^^^ ^^.^^ therefore consists of iron 0-77, oxigen 0-23. 



* Mr. Bucholz insists much on the smell of phosphorus, or of 

 phosphuretted hidrogen gas, emitted when ferruginous salts are 

 precipitated by ammonia. 



Examination 



