ON THE ASSAYING OF COALS BY THE BLOWPIPE. 217 



any portion of the fine light ash. Finally, when the ash ceases to ex- 

 hibit in any of its parts a black colour, the lid of the capsule is to be 

 cautiously replaced, and the whole cooled and weighed,* 



Nature of the Ash : — As already remarked, the ash or inorganic 

 portion of the coal, may be either argillaceous — consisting, in that case, 

 essentially of a sub-silicate of alumina — or calcareous ; and in either 

 case, ferruginous also. If free from iron, the ash will be white or pale 

 grey ; but if iron be present, it will exhibit a yellowish, brown, or red 

 colour, according to the amount of iron contained in it. The iron is, 

 of course, in the state of sesqui-oxide, derived, except perhaps in a few 

 rare instances, entirely from the iron pyrites or bi-sulphide of iron 

 originally present in the coal. I have found, from numerous trials, 

 that the well known salt of phosphorus test, so useful in general 

 cases for the detection of siliceous compounds, cannot be safely resorted 

 to for the purpose of distinguishing the nature of the coal ash obtained 

 in these experiments. This is owing to the small quantity of ash, and 

 to the extremely fine state of division in which it is obtained. Argil- 

 laceous ashes dissolve in salt of phosphorus with as much facility as 

 as those of a calcareous nature, and without producing the character- 

 istic silica-skeleton, or causing the opalization of the glass. With cal- 

 careous ashes also, the amount obtained is never sufficient to saturate 

 even an exceedingly minute bead of borax or salt of phosphorus, and 

 hence no opacity is obtained by the flaming process. The one kind of 

 ash may be distinguished, however, from the other, by moistening it, 

 and placing the moistened mass on a piece of reddened litmus paper. 

 Calcareous ashes always contain a certain amount of caustic lime, and 

 thus restore the blue colour of the paper. These calcareous ashes also, 

 sometimes contain sulphate of lime.f For the detection of the latter, 

 the following well known test may be resorted to. The ash is to be 

 fused with carb. soda and a little borax on charcoal in a reducing 

 flame, and the fused mass, thus obtained, is to be moistened and placed 

 on a bright silver coin, or on a piece of glazed card : when, if sulphate 

 of lime were present in the ash, a brown or black stain will be produced 

 by the formation of sulphide of silver or of lead. In testing earthy 

 sulphates generally by this process, a little borax should always be 



• If the ash be very ferruginous, the results thus obtained, to be exact, will require cor- 

 rection : the original iron-pyrites of the coal being weighed as sesqui-oxide of iron. In ordi- 

 nary cases, however,— i(i est, in assays as distinguished from analyses, this may be fairly 

 neglected. 



When also, the ash is calcareous, and in considerable quantity, it should be moistened vrtth 

 a drop of a solution of carbonate of ammonia, and gently re-heated, previous to weighing. 



t The ashes of a lignite from Grosspreisen yielded Erdmann :— Carbonate of lime 30.93, 

 sulphate of lime 36 . 42, lime 17 . 22, sesqui-oxide of iron 20 . 67, alumina 1 . 23, soda 1 . 86, potash 

 1.67- 



VOL. III. P 



