440 Prof. Chapman on the Assaying of Coals by the Bloivpipe. 



the camel's-hair pencil or small colour-bnish belonging to the 

 balance-case. The weighing capsule should also be placed in 

 the centre of a half-sheet of glazed writing-paper, to prevent the 

 risk of any accidental loss during the transference. After the 

 weighing, the operation must always be repeated, to ensure that 

 no further loss of weight occur. In place of the blowpipe-lamp, 

 the spirit-lamp may be employed for this operation ; but with 

 the former there is less danger of the heat becoming too high. 

 By holding a slip of glass for an instant, every now and then, 

 over the capsule, it will soon be seen when the moisture ceases 

 to be given off. It should be remarked, that some anthracites 

 decrepitate slightly when thus treated, in which case the por- 

 celain capsule must be covered with a small watch-glass. 



Estimation, ^c. of Coke. — In this operation the small crucible 

 is employed. Particles are detached from the assay specimen 

 as before, by the cutting pliers, and about 100 or 150 milli- 

 grammes taken for the experiment. The weighing is performed 

 in the crucible itself, this being placed in the little weighing- 

 capsule, with its handle-support projecting over the side. The 

 crucible, with its cover on, is then brought gradually before the 

 blowpipe to a red heat. The escaping gases will take fire and 

 burn for a few seconds on the outside of the vessel, and a small 

 amount of carbonaceous matter may be deposited upon the 

 cover. This, however, rapidly burns off on the heat being con- 

 tinued; and as soon as it disappears, the crucible is to be with- 

 drawn from the flame, cooled quickly, and weighed always with 

 its cover on. The loss, minus the weight of moisture as ascer- 

 tained in a previous experiment, gives the amount of volatile or 

 gaseous matter. The residue is the coke and its contained ash. 

 The coke should be examined by a magnifying glass, and its 

 general aspect and characters noted down. As already ex- 

 plained, some coals yield a swollen, semi-fused, and aggluti- 

 nated coke, with a mammillated surface and metalloidal aspect. 

 Others produce a slightly fritted and partially agglutinated 

 coke ; others again, an unfused coke retaining the form of the 

 coal fragments subjected to the assay; others a pulverulent, or 

 a strongly- soiling coke, and so on. It is sometimes desirable to 

 take the specific gravity of the coke. 



Estimation of Ash. — The platinum capsule is employed for 

 this operation. The coal must be reduced to a coarse powder, 

 and about 150 milligrammes weighed out for the experiment. 

 The weighing may be effected in the platinum capsule in which 

 the experiment is to be performed. The weight ascertained, the 

 platinum capsule is to be fixed in an inclined position above the 

 spirit-lamp, and heated as strongly as possible. If the wick of 

 the spirit-lamp be pulled up sufficiently, and a very thin capsule, 



