Infellig£nce andiMiii^lltineous Articles, 403 



t^ie weight of which served to ealculabe the oxygen contained in the 

 najneral above the protoxide. 



jjhThe liquor derived from treating the black mineral with hydro* 

 «hl6ric acid was filtered, then evaporated to dryness to separate some 

 flocculi of silica, and again filtered ; the manganese, iron and lime 

 were separated by the means already described ; no magnesia was 

 found. i.;,M,i,,^ 



..liThe tesidueiunattackedby the hydrochloric acid was calcined and 

 weighed, the gelatinous silica was then separated by liquid potasHt 

 tlie portion insoluble in the alkali consisted of small rose-coloureil 

 grains, which, examined by the glass, appeared to be perfectly simi'- 

 lar to the bisilicate from the centre of the specimen. In fact, by 

 acting upon this matter by carbonate of soda in the platina crucible, 

 there was separated by acid 0'48 of its weight of gelatinous silica, a 

 quantity very near that obtained by the analyses of the bisilicate. ;•) 

 To estimate the water of the black mineral, a portion of it was 

 heated in hydrogen, by employing a platina crucible with a tubulated 

 cover ; a greenish substance was obtained which was acted upon by 

 hydrochloric acid without evolving any chlorine. The loss of 

 weight of the mineral heated in the hydrogen consisted of, — 1st, the 

 water ; 2nd, the oxygen above that which corresponded to protoxide, 

 which was known by the weight of the sulphate of barytes, so thatt 

 the difference of the loss in the current of hydrogen wou^d give the 

 water. baliod ^hioR vlb Aim hBiBiuiRB ssivf 



, fhe results of theL^naLy^ea.jy^iBfotamB Afivr I)9?x5f ntn» rrArfj .indq 

 uAi ai IWaXer. . ,'^'^f,Qaui Qiii.iJ&iaosams.'io. eiiidq- 10* 14 .j/slfixo 

 — : aw 'Oxygen , .': .■';'r.-L'-i!;^'3dlla sdluiai siX . .oj.i:si^j94 lu olai? 

 Protoxide of manganese. ......... • a^^ko- 43'00 



Peroxide of iron . :^^.,^f^^^i^ ^^ bbUCJbW f ^J 



^^^^ • V • • : • Wol? ^n.^blitc53t)'iT i ^^ 



, 11, -J f Gelatmous sinca 2*40 



Insoluble residue | q-^^^^^^^ ^^^^ted upon 27-20 



99-60 

 When it is considered that the rose-coloured silicate is acted upon 

 by boiling in hydrochloric acid, it will be admitted as probable, that 

 the small portion of gelatinous silica occurring in the analyses' is 

 derived from a portion of the bisilicate. Admitting this supposition, 

 and subtracting from the quantity of protoxide of manganese fottnd 

 that which corresponds to the gelatinous silica, and which is 2 -It), 

 the remainder, 40-90, contains a quantity of oxygen equal to that 

 occurring in the sulphurous acid. It may also be concluded that the 

 black substance is a mixture of hydrates of f)eroxide of man^tie^e 

 and iron, with a certain proportion of unaltered bisilicate. iiil'H 

 If also this composition be compared with that of the ro3^-co- 

 feured matter, it will be seen, — 1st, that the silica and the magnesia 

 have completely disappeared during decomposition, as well as the 

 greater part of the lime ; 2nd, that the protoxides of iron and of 

 manganese are converted into hydrates of peroxides, and occur in 

 the black substance in the same relation as in the unaltered mineral. 

 -^Ann. des Mines, tome vn.'-'-^"^ JjUi. Uolxoc! ijiyj^ iu<si!jn'[Ur< lo 



2D2 



