476 Intelligence and Miscellaneous Articles. 



This salt is unalterable by exposure to the air ; when treated with 

 cold water the crystals lose their transparency, but nearly retain their 

 form. — Ann. de Ch. et de Phys., Avril 1844. 



ON THE IDENTITY OF SCORODITE AND NEOCTESE. 



9tq I 



BY M. DAMOUR. 



M. Descloizeau having found that these substances agreed per- 

 fectly in their primary form, viz. a right rhombic prism, and in the 

 various modifications to which it is subject, M. Damour undertook a 

 fresh analysis of them, that of Berzelius not agreeing with the pre- 

 vious one of Ficinus. For this purpose crystals of scorodite from 

 Vaulry (Haute Vienne), from Saxony and Cornwall, and of the 

 neoctese of Brazil, from the collection of the Ecole des Mines, were 

 examined. 



The specific gravity of scorodite of Vautry was found to be 3*11, 

 and that of the neoctese of Brazil 3- 18 ; when heated in a tube both 

 of them yielded water, which did not alter litmus paper ; the residual 

 matter was opake and of a grayish-yellow colour ; no arsenious acid 

 sublimed when pure crystals were operated on ; before the blowpipe 

 both substances swell up and are reduced to blackish-gray globules ; 

 on charcoal they yield arsenical odour, and a black scoria which 

 obeys the magnet. Nitric acid, whether hot or cold, does not act 

 upon scorodite or neoctese, but hydrochloric acid readily dissolves 

 them, and the solution is of a brown colour ; this is decomposed by 

 ammonia, partially ; the precipitate formed is of a brown colour. 



The powder of these minerals when placed on a fragment of caustic 

 potash, instantly assumes a rust colour, without any admixture of 

 blackness ; the hydrochloric solution, mixed with the chloride of 

 sodium and gold, gives no trace of reduced gold. These experiments 

 prove that the minerals in question are of the same nature, and that 

 the oxide of iron which they contain is the peroxide ; in order to de- 

 termine the proportions of the constituents of these minerals the fol- 

 lowing experiments were performed : — 



The mineral, reduced to powder and dried in vacuo at the usual 

 temperature, was dissolved, with heat, in concentrated hydrochloric 

 acid ; the solution took place rapidly. The liquor was diluted with 

 water and dropped gradually into a phial containing ammonia and 

 hydrosulphate of ammonia. The mixture was digested at a tempe- 

 rature of 122° to 140° Fahr., and at the expiration of twenty-four 

 hours, the precipitated sulphuret of iron formed was collected on a 

 filter and properly washed (A.). The sulphuret of iron, while moist, 

 was dissolved in aqua regia, and then precipitated by means of am- 

 monia ; the liquor (A.) separated from the sulphuret of iron was 

 rendered slightly acid by acetic acid, and after some time yellow 

 sulphuret of arsenic was precipitated ; in order to ascertain the pro- 

 portion of arsenic which it contained, this sulphuret, previously dried 

 in vacuo, was acted on by aqua regia ; globules of sulphur remained, 

 which were collected and weighed ; the acid liquor contained arsenic 

 and a little sulphuric acid formed from the sulphur, the quantity of 



