442 Prof. Chapman on the Assaying of Coals by the Blowpt^^. 



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

 that case, esentially of a subsilicate 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 

 sesquioxide, derived, except perhaps in a few rare instances, 

 entirely from the iron pyrites or bisulphide 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 the ash, and to the extremely fine state of 

 division in which it is obtained. Argillaceous ashes dissolve in 

 salt of phosphorus with as much facility as those of a calcareous 

 nature, and without producing the characteristic silica skeleton, 

 or causing the opalization of the glass. With calcareous 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 sometmies following 

 contain sulphate of lime*. For the detection of the latter, the 

 well-known test may be resorted to. The ash is to be fused with 

 carbonate of 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 added to the carbonate 

 of soda, in order to promote the solution of the assay, and the 

 more ready formation of an alkaline sulphide. If oxide of man- 

 ganese be present in the ash, by fusion with carbonate of soda 

 and a little borax, we obtain the well known bluish-green man- 

 ganate of soda technically termed a turquoise-enamel. 



Estimation of Sulphur. — The method of detecting the presence 

 of sulphur in coal, is the same as that just pointed out for the 

 detection of sulphate of lime in the ash. The actual estimation 



be moistened with a drop of a solution of carbonate of ammonia, and gently 

 re-heated previous to weighing. 



• The ashes of a lignite from Grosspreisen yielded Erdmann, — Carbo- 

 nate of lime, .30-93; sulphate of lime, 36-42; lime, 17'22; sesquioxide of 

 iron, 20-67; alumina, 123; soda, 1-86; |)Otash, 1-67. 



