CONTRIBUTIONS TO BLOWPIPE ANALYSIS. 351 



as high as 6 or 7, and even reaches 15 or 20 per cent, in certain lig- 

 nites. Where large quantities of coal are consumed, therefore, a 

 serious loss is entailed on the purchaser unless the moisture be proper- 

 ly determined and allowed for. 



Estimation, &c., of CoTce : — In this operation, a small crucible of 

 platinum is most conveniently employed. This may consist of a couple 

 of i-ather deep spoons — the larger one without a handle, so as to ad- 

 mit of being placed over the smaller spoon, as in the 

 annexed figure : thus serving as a lid. The long 

 handle of the crucible-spoon must be bent as shown 

 in the drawing, in order that the spoon may retain an 

 upright position when placed on the pan of the balance. 

 The spoon-crucible of this kind employed by the writer, weighs (with 

 its lid) only 2.33 grammes, or rather less than 36 grs. About 150 

 milligrammes of coal are detached as before, in"several small fragments, 

 from the assay-specimen. These may be weighed directly in the cruci- 

 ble, the latter being placed in the little weighing capsule of horn or 

 brass, with its handle-support projecting over the side of this. The 

 crucible, with its cover on, is then taken up by a convenient forceps 

 (see the note on page 19) and brought gradually before the blowpipe to a 

 red heat. The escaping gases will take fire and burn for a few seconds 

 around the vessel, and a small amount of carbonaceous matter may be 

 deposited upon the cover. This rapidly burns off, however, on the 

 heat being continued. As soon as it disappears, the crucible is to be 

 withdrawn from the flame, and placed on the blowpipe-anvil to cool 

 quickly. Its weight is then ascertained : always without removing 

 the cover. The loss, minus the weight of moisture as found by the 

 first process, gives the amount of volatile or gaseous matter. The 

 residue is the coke and its contained ash. The coke in some anthracites 

 exceeds 89 or 90 per cent. In anthracitic or dry coals it usually varies 

 from 70 to 80 per cent., and the fragments are sometimes slightly 

 agglutinated. In ordinary bituminous or caking coals, it amounts in 

 general to about 65 or 70 per cent., and presents a fused and mamiU 

 lated surface. In cannel or gas coals, the per centage of coke may be 

 assumed to equal 50 or 60, but it is sometimes as low as 30. The coke 

 fragments are often partially agglutinated, but they never present a 

 fused, globular aspect. Finally, in lignites or brown coals, the coke 

 may vary from 25 to 50 per cent. It forms sharp-edged fragments of 

 a dull charcoal-like appearance, without any signs of fusion. 



Vol. X. X 



