216 ON THE ASSAYING OF COALS BY THE BLOWPIPE. 



150 milligrammes weighed out for the experiment. The weighing may 

 be efFected in the platinnm capsule in which the experiment is to he 

 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, as already directed, be employed, a temperature 

 sufficiently high to burn off the carbon from most coals is in this 

 manner attainable. The lid of the capsule must be placed above the 

 coal-powder until combustion cease, that is to say, until the gaseous 

 products be driven ofP, and only the uninflammable carbon and ash 

 remain : as, otherwise, a portion of the powder might very easily be 

 lost. Some of the anthracites, also, decrepitate on the first application 

 of the flame ; but even if decrepitation rarely ensue when the coal is in 

 the form of powder, it is still advisable in all cases to keep the assay 

 covered until the flame cease. During the after combustion, the pow- 

 der or small particles must be gently stirred and carefully turned over, 

 and if agglutinated, broken down by a light steel spatula, or, better still, 

 by a small spatula of platinum, made by inserting a strip of stout 

 platinum foil (an inch long) into one of the ivory or wooden handles 

 intended to hold platinum spoons. These handles are 

 quite useless for the latter purpose, or at least are far 

 inferior to the steel forceps described above. With /\- 



the forceps, for example, the spoons can be taken up 

 and disengaged in an instant, and without the inter- c 

 vention of the right hand. Whilst the spoons also, 

 are still red hot, the forceps may be laid down with- b 

 out the spoons coming in contact with the table. 

 Figure 4 shews the form and size of the spatula that 

 I employ. A is the ivory handle ; C the piece of 

 stout platinum foil fitting into a slit in A ; and B the 

 metal ring which keeps the two together. The a 

 platinum, it should be remarked, must be sufficiently 

 stout to resist bending ; and its point must be kept 

 quite bright and smooth by occasional polishing on a 

 smooth part of the agate mortar which always accom- 

 panies the blowpipe. If by the method of procedure 

 just described, the carbonaceous matter be not finally 

 burnt ofi', the flame of the blowpipe — using the oil- 

 lamp, or spirit-lamp with the wick well up — may be employed to ac- 

 celerate the process. The operator, however, must be careful to keep 

 the capsule inclined away from the flame, in order to avoid the loss of 



