CONTRIBUTIONS TO BLOWPIPE ANALYSIS. 353 



lerate the process ; but the operator must blow cautiously, and direct 

 the flame only against the under side of the capsule, in order to avoid 

 the risk of loss. Finally, on the ash ceasing to exhibit in any of its 

 particles a black color, the lid of the capsule is to be carefully replaced, 

 and the whole cooled and weighed,* 



In good coals, the amount of ash is often under 2 per cent., and it 

 rarely exceeds 4 or 5 per cent. In coals of inferior quality, however, 

 it may vary from 8 or 10 to even 20 per cent. As regards its compo- 

 sition, the ash may be : — (1) argillaceous, consisting essentially of a 

 silicate of alumina ; (2) argillo-ferruginous ; (3) calcareous ; and (4) 

 calcareo-ferruoinous. If free from iron, it will be white or pale grey ; 

 but if more or less ferruginous, it will present a red, brown, or yellow- 

 ish color. Phosphor-salt, so useful in general cases for the detection 

 of siliceous compounds, cannot be safely used to distinguish the nature 

 of the ash obtained in blowpipe assays. Owing to their fine state of 

 division and to the small quantity at command, argillaceous ashes dis- 

 solve in this reagent with as much facility as those of a calcareous 

 nature, and without producing a characteristic silica skeleton, or 

 causing the opalization of the glass. With calcareous ashes also, the 

 amount obtained is rarely sufficient to saturate even an exceedingly 

 minute bead of phosphor-salt or borax, and hence no opacity is pro- 

 duced by the flaming process. The one kind of ash, may be distin- 

 guished, nevertheless, from the other, by moistening it, and placing 

 the moistened mass on reddened litmus-paper. Calcareous ashes 

 always contain a certain amount of caustic lime, and thus restore the 

 blue color of the paper. These calcareous ashes, also, though princi- 

 pally composed of carbonate of lime, sometimes contain small portions 

 of phosphate and sulphate of lime. The presence of the latter may 

 be readily detected by the well known production of an alkaline sul- 

 phide by fusion with carbonate of soda in a reducing flame — the fused 

 mass exhibiting a reddish color, and imparting when moistened a dark 

 stain to a plate of silver or piece of lead test-paper. The latter may 



* If the ash be very ferruginous-— in which case it will present a red or tawny 

 color — the results, as thus obtained, will require correction : the original iron 

 pyrites of the coal being weighed as sesquioxide of iron. In ordinary assays, 

 however — as distinguished from analyses — this may be fairly neglected. When 

 also the ash happens to be calcareous and to occur in large quantity, it should 

 be moistened wiih a drop or two of a solution of carbonate of ammonia, and 

 gently heated, previous to being weighed. 



