CONTRIBUTIONS TO BLOWPIPE ANALYSIS. 349 



easily distinguished by its color, however, from the deep orange anti-- 

 monial sulphide. The crystalline character, etc., of this sublimate,, 

 would also effectually prevent any chance of misconception. 



12. THE COAL ASSAY. 



[First published in the Canadian Journal : May, 1858 ; and in the Philo- 

 sophical Magazine for July of that year.] 



In the practical examination of Coals, the following operations are 

 essentially necessary :* — (I) The estimation of the water or hygro- 



* To these might be added, the determination of the heating powers or "abso-- 

 lute warmth " of the coal, but this may always be estimated with sufficient 

 exactness for practical purposes by the amount of coke, ash, and moisture, as 

 compared with other coals. Properly considered, the litharge test, resorted to 

 for the determination of the calorific power of coals, is of very little actual value. 

 The respective results furnished by good wood charcoal and ordinary coke, for 

 example, are closely alike, if not in favour of the charcoal ; and yet experience 

 abundantly proves the stronger heating powers of the coke. In practice, more- 

 over, the actual value of a coal does not always depend upon the "absolute 

 warmth " of the latter, as certain coals, such as brown coals rich in bitumen, 

 may possess beating powers of con-iderable amount (as estimated by the reduc- 

 tion of litharge) though only of brief duration. Thus, the lignites of the depart- 

 ment of the Basses Alpes in south-eastern France, and those of Cuba, yield with 

 litharge from 25 to 26 parts of reduced lead ; whilst many caking coals, practi- 

 cally of much higher heating power, yield scarcely a larger amount. When 

 pyrites also is present in the coal — a condition of very common occurrence — 

 the litharge test becomes again unsatisfactory, the pyrites exerting a reducing 

 action on the lead compound. 



As described, however, by Bruno Keri,, in quoting the writer's Coal Assay 

 (Lothrohr-Untersuchungen : Zweite Aiifi. 1862, p. 146) the so-called absolute 

 warmth or heati -g power of a coal sample may be determined, if desired, in 

 blowpipe practice, by the following modification of Berthiee's method : — 20 

 milligrammes of the coal, in fine powder, are to be mixed intimately with 500 

 milligrammes of oxy-chloride of lead (consisting of 3 parts of litharge + 1 part 

 of chloride of lead, fused together and finely pulverized). The mixture is to be 

 placed in a blowpipe-crucible, and covered with about an equal amount of the 

 lead compound, a second cover of 8 blowpipe-spoonfuls of powdered glass -i- 1 

 spoonful of borax, being spread over this. The crucible, covered with a clay 

 capsule, is then to be fitted into a charcoal block in the ordinary blowpipe fur- 

 nace, over which a charcoal lid is placed, and tie flame directed against its 

 ■under side, so as to keep it at a red heat for from 5 to 8 minutes. The weight 

 of the reduced lead divided by 20 gives the amount of the lead mixture reduced 



