^68 MAGNETICAL PYRITES. 



Partly folublc The magnetical pyrites, when digefled in dilute fulphuric 



acid!' lUefUlph ' acid ' is P artialI y diflblved, with little effervefcence, although 

 there is a very perceptible odour of fulphuretted hydrogen. 

 The folution is of a very pale green colour. 

 Precipitates. Pure ammonia produced a dark green precipitate, tending to 



black; and pruffiate of pota(h formed a very pale blue preci- 

 pitate, or rather a white precipitate mingled with a lmall portion 

 of blue. The whole of the latter, however, by expofure to the 

 air, gradually aflumed the ufual intend ty of Prufiian blue; and 

 the blackifh green precipitate, formed by ammonia, became 

 gradually ochraceous. Thefe effedts therefore fully prove, that 

 the iron in the folution was, for the greater part, at the minimum 

 of oxidizement, fo as to form the green fulphate, and white 

 pruffiate, ot iron;* and, confequently, that the iron of the 

 magnetical pyrites is either quite, or very nearly, in the ftate 

 of perfect metal. 

 Effea of nitric This pyrites, when treated with nitric acid, of the fpecific 

 aa gravity of 1.38, diluted with an equal quantity of water, is at 



fir ft but little affected ; but, when heat is applied, it is diflblved, 

 with much effervefcence, and difcharge of nitrous gas ; the 

 effervefcence, however, is by no means fo violent as when the 

 common pyrites are treated in a fimilar manner. It is alfo 

 worthy of notice, that if the digeflion be not of too long dura- 

 tion, a confiderable quantity of fulphur, infubjiunce, is Separated; 

 whilft, on the contrary, fcarcely any can be obtained from the 

 common pyrites, when treated in a fimilar manner; although I 

 fhall foon have occafion to prove, that the real quantity of 

 fulphur is much more confiderable in the latter than in the 

 former. 

 Of muriatic As foon as muriatic acid is poured on the powder of the 



acid. magnetical pyrites, a flight effervefcence is produced, which 



becomes violently increafed by, the application of heat; a 

 quantity of gas is difcharged, which, by its odour, by its in- 

 flammability, by the colour of the flame, by the depofition of 

 fulphur when burned, and by other properties, was proved to 

 be fulphuretted hydrogen. 



During the digeflion, fulphur was depoflted, which fo en- 

 veloped a fmall part of the pyrites, as to protect it from the 

 farther action of the acid,. 



* Recherches fur le Bleu de PrufTe, par M. Prouft. Annales de 

 Clrimie, Tome XXIIL p, 85. 



The 



