216 Dr Turner's Chemical Examination of Wad. 



and friable, and soils when handled. Its streak and powder 

 are of a reddish-brown colour. It absorbs moisture greedily 

 on being wetted, and when put into water emits numerous 

 globules of air with a hissing noise. Its specific gravity, after 

 its contained air is expelled, is 3.024. It separates readily 

 into parallel layers, the natural joinings being formed by thin 

 strata of hydrated peroxide of iron, which is largely and 

 intimately mixed with the wad, so as not to be separable 

 from it. 



The Derbyshire Wad, when digested in muriatic acid, leaves 

 a white residue, chiefly consisting of sulphate of lime, which 

 is interspersed in minute crystals through the mineral. Its 

 quantity is variable ; but in the portion submitted to analysis 

 it amounted to 2.74 per cent. 



The clear solution in muriatic acid was strongly coloured 

 with iron, and on the addition of sulphuric acid yielded a 

 quantity of sulphate of baryta, corresponding to 5.40 of pure 

 baryta. The liquid was then exactly neutralized, and the iron 

 precipitated by benzoate of ammonia. The filter containing 

 the benzoate of iron was put into a platinum crucible, a few 

 drops of nitric acid and solution of nitrate of ammonia were 

 added, the paper after being dried by a sand heat was burned, 

 and the residue ignited. By this means the benzoic acid and 

 filter may be decomposed without deoxidizing any of the per- 

 oxide of iron. The resulting peroxide, which was not in the 

 slightest degree attracted by the magnet, amounted to 52.34 

 per cent. 



From the solution, thus freed from baryta and iron, the 

 manganese was thrown down by potash, and a quantity of 

 red oxide obtained equivalent to 38.59 per cent, of deutoxide. 

 — The solution also contained a trace of lime. 



Carefully dried at 21 2**, and exposed to a red heat, it lost 

 1 0.29 per cent, of water. No oxygen was expelled by that 

 temperature, showing that the manganese is not in a higher 

 state of oxidation than the deutoxide. It appears, accord- 

 ingly, that this variety of Wad, besides oxide of iron and 

 water, contains a compound of baryta and deutoxide of manga- 

 nese, apparently similar to that constituting the essential in- 

 gredient in the uncleavable ore of manganese, and which is 

 present in small quantity in the Devonshire Wad. 



