350 CONTRIBUTIONS TO BLOWPIPE ANALYSIS. 



metric moisture present in the coal ; (2) the determination of the 

 weight and character of the coke ; (3) the estimation and examination 

 of the ash or inorganic matters ; and (4) the estimation of the sul- 

 phur, chiefly present in the coal as FeS^. 



Estimation cf Moisture .-—This operation is one of extreme sim- 

 plicity. Some slight care, however, is required to prevent other 

 volatile matters from being driven off during the expulsion of the 

 moisture. Seven or eight small particles, averaging together from 

 1 00 to 150 milligrammes, are to be detached from the assay specimen 

 by means of the cutting pliers, and carefully weighed. They are then 

 to be transferred to a porcelain capsule with thick bottom, and strongly 

 heated for four or five minutes on the support attached to the blow- 

 pipe lamp, the unaided flame of the lamp being alone employed for 

 this purpose. It is advisable to place in the capsule, at the same time, 

 a small strip of filtering or white blotting-paper, the charring of which 

 vdll give indications of the temperature becoming too high. The coal, 

 whilst still warm, is then to be transferred to the little brass capsule 

 in which the weighings are performed, and its weight ascertained. In 

 transferring the coal from one vessel to the other, the larger pieces 

 should be removed by a pair of fine brass forceps, and the little parti- 

 cles or dust afterwards swept into, the weighing capsule by means of 

 the camel's-hair pencil or small colour-brush 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 acciden- 

 tal 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 

 porcelain capsule must be covered at first with a small watch-glass. 



In good samples of coal, the moisture ought not to exceed 3 or 4 

 per cent., but in coals that have been long exposed to damp it is often 



by 1 part of the coal. One part of pure carbon reduces 34 parts of this mixture ; 

 one part of charcoal, 30-33 parts ; one part of bituminous coal, 19-33 ; one part 

 of brown coal, H-26 j one part of peat, 8-2Y; and one part of wood, 12-18 

 parts. 



