328 



OXIDATIONS OF IRON. 



\ve shall not be able to explain it, till these facts hare beeA 



more thoroughly studied, than has yet been in my power. 



Classification of Meantime I would propose, for convenience, the follow- 



r?frd\° e dlc- h ing c * assincation and nomenclature. All substances, appli* 



tricity. ed to the poles of the pile are either, Class 1, insulators ; 



or they are conductors. The latter are distinguishable into, 



Class 2, perfect conductors ; and imperfect conductors* 



The imperfect are, Class 3, bipolar imperfect conductors : 



Class 4, positive unipolar : and Class 5, negative unipolaf* 



III. 



Inquiries concerning the Oxidations of Iron ; by Mr. Darso*. 



(Concluded from p. 280.^ 



Farther differ- JL DISSOLVED six grains of iron in muriatic acid without 

 ences in the ^^ . an( j at ^ sarae time, in a separate vessel, six grains 

 bysuiphuretted of red oxide, which I saturated with sulphuretted hidrogen. 

 kutrogen. Four hours after I precipitated both these solutions by an 



alkali, and I found, that the precipitates of the green so- 

 lution by sulphuretted hidrogen passed to red with the 

 greatest rapidity. On pouring off the supernatant fluid, 

 and letting water fall from some height on the oxide, it 

 turned red immediately ; but the precipitates of the other 

 solution resist this trial. The green oxide by sulphuretted 

 hidrogen, redissolved in muriatic acid, precipitates red ; or 

 at least it does so after two solutions. The common green 

 oxides of iron, when recent, retain their colour even after 

 being redissolved in acids five or six times. The reason of 

 this no doubt is, that in the common green solutions of 

 iron the hidrogen combines with the iron in the state of nas- 

 cent gas, or very dense, and forms a more solid combina- 

 tion, than that into which the hidrogen furnished by sul- 

 phuretted hidrogen enters Avith the red oxide. 

 The green ox- If the green oxides of iron be hidrurets, as I suppose, it 



id.es hidrurets. is easy to account for the alteration, that the green salts of 

 This explains J T . D 



their alteration iron undergo by exposure to the air. It is not to be won- 

 in the air. dered at, that hidrogen combined with oxide of iron should 



be volatilised spontaneously at a heat above 10° [54y u F.]. 



Almost 



