102 Dr. Turner's Chemical Examination 



Subtracting 2*784 as impurities, there remain 97*214 parts, 

 which lose 11*599, or 11*931 per cent, of oxygen in being 

 converted into the red oxide. It is therefore an anhydrous 

 peroxide, most probably containing an admixture of some 

 other oxide. 



Analysis of Psilomelane, or the Uncleavable Manganese-ore. 

 — Tliis mineral when reduced to powder has a brownish-black 

 colour. With sulphuric acid it does not emit any odour of 

 chlorine. It dissolves completely in muriatic acid, excepting 

 a small quantity of silica which amounts to 0*26 per cent ; and 

 the only substances which I could detect in the solution are 

 baryta and the oxide of manganese. Though this ore has been 

 placed by mineralogists among the oxides of iron, under the 

 names of Black Hematite and Black Iron-ore, pure fragments 

 of it do not contain a trace of that metal. 



When heated to redness psilomelane gives out 6*216 per 

 cent of water. The diminution in weight occasioned by ex- 

 posure to a white heat is 13*58 per cent; and on subtracting 

 6*216 for water, there remains 7*364 as the loss in oxygen. 



To ascertain the quantity of baryta 30*028 grains of the mi- 

 neral were dissolved in muriatic acid, and the baryta precipi- 

 tated by means of the sulphate of soda, a considerable excess 

 of muriatic acid being allowed to remain in the liquid, to pre- 

 vent any manganese from adhering to the precipitate. The 

 sulphate of baryta, after exposure to a red heat, amounted to 

 7*434 grains, equivalent, according to the atomic numbers of 

 Dr. Thomson, to 4*914 grains, or 16*365 per cent of pure 

 baryta. 



According to this analysis, 100 parts of psilomelane have 

 yielded of 



Red oxide 69*795 



Oxygen 7*364 



Baryta 16*365 



Silica 0*260 



Water 6*216 



100*000 

 The precise atomic constitution of psilomelane is not made 

 apparent by this analysis ; and, indeed, the result is of such a 

 nature as to leave no doubt of this mineral containing more 

 than one oxide of manganese. For it follows, from the quan- 

 tity of oxygen expelled by heat, that a considerable part of 

 the manganese must be in the form of peroxide; but it is 

 equally clear that the whole of it cannot be in that state, be- 

 cause 69*795 parts of red oxide require 9*627 instead of 7*364 

 parts of oxygen to constitute the peroxide. On perceiving 



this 



