uinahjsts of the magnet ical Pyrites, 1 37 



as when the comnion pyrites are treated in a similar man- 

 ner. It is also worthy of notice, that if the digestion be 

 not of too long duration, a considtraljle quantity of sul- 

 phur, in substance, is separated ; whilst, un the contrary, 

 scarcely any can be obtained from the cunniion pyrites, 

 when treated in a similar manner; although I shall soon 

 have occasion to prove that the real quantity of sulphur is 

 niuch more considcraole in the latter than in the former. 



As soon as muriatic acid is potu'cd on the }X)wder of the 

 magnetical pyrites a slight efiervescence is produced, which 

 becomes violentlv increased by the application of heat ; a 

 quantity of gas is discharged, which, bv its odour, by its 

 jnflannnabilitv, by the colour of the flame, by the deposi- 

 tion of sulphur when burned, and bv other properties, was 

 proved to be sulphuretted hydrogen. 



Durinsr the digestion sulphur was deposited, which so 

 enveloped a small part of the pyrites as to protect it from 

 the further action of the acid. 



The solution was of a pale vellowish green colour. With 

 prussiate of potash it atrbrded a pale blue precipitate, or 

 rather a white precipitate mixed with blue; and with am- 

 monia it formed a dark blackish-green precipitate, which 

 gradually became ochraceous ; so that these eiiecta corro- 

 borated the conclusions which v. ere founded on the pro- 

 perties of the sulphuric t-olution, namely, that the iron con- 

 taitied in the pyrites is almost, if not quite, in the nieiallic 

 state. 



Otl'.er experiments were made ; but, as they merely con- 

 firm the above observation;, I shall proceed to give an ac- 

 count of the analvsif . 



§ IV. 

 Anahjm of the mapietical Pyrites. 



A. 100 grains, reduced to a Hne powder, were digested, 

 with two ounces of muriatic acid, in a glass matrass placed 

 in a sand-bath. The effects already described took place, 

 and a pale vello-vish green solution was formed. The resi- 

 duum was then again diiiested with two parts of muriatic 

 acid mixed with one of nitric acid ; and a quantity of pure 

 sulphur was obtanied, which, being dried, weighed 14 

 grains. 



B. The acid in which the residuum had been digested wa« 

 added to the first muriatic solution ; some nitric acid wa<. 

 also poured in, to promote the oxidizement of the iron, and 

 thereby to facilitate the precipitation of it by ammonia, which 



was 



