352 CONTRIBUTIONS TO BLOWPIPE ANALYSIS. 



Estimation of Ash or Inorganic Matters ; — A platinum capsule is 

 employed for this operation. One of about half an inch in diameter, 

 with a short ear or handle, is sufficiently large. A somewhat smaller 

 capsule, with its handle cut off, may be fitted into this (in reversed 

 position) to serve as a lid. The weight of the two together need not 

 exceed 2\ or 21 grammes.* The coal must be reduced to a coarse 

 powder, and about 150 milligrammes weighed out for the experiment. 

 The platinum capsule is then to be fixed in a slightly-inclined posi- 

 tion above the spirit-lamp, and heated as strongly as possible. If the 

 wick of the spirit-lamp be raised sufficiently, and the capsule be light 

 and thin, the temperature will be sufficient to burn oif the carbon : at 

 least, in the majority of cases. The lid of the capsule must be placed 

 above the coal powder until combustion cease, and all the more gas^ 

 eous products are driven off, as otherwise, a portion of the powder 

 might very easily be lost. During the after combustion, the powder 

 must be gently stirred, and if agglutination take place, the particles 

 must be carefully broken up, by a light steel-spatula or by a piece of 

 stout platinum-wire fiattened at one end. If the carbonaceous matter 

 be not burnt off by this treatment, the blowpipe may be used to acce- 



* It is convenient to have counterpoises for the platinum vessels described 

 above, as the weights which accompany the blowpipe-balance only range, in 

 general, from a gramme downwards. A small platinum capsule forms an excel- 

 lent counterpoise. It can be trimmed down by a pair of fine scissors until 

 brought by repeated trials to the proper weight. The writer has cut out recep- 

 tacles for two platinum vessels and counterpoises of this kind, in the little box 

 into which his travelling balance packs ; and he recommends other operators to 

 do the same, as these vessels are of very convenient use, not only in coal assay- 

 ing, but in ascertaining the amount of water in minerals, as well as for other 

 purposes. 



These platinum vessels are held most conveniently, during ignition, by a pair 

 of steel forceps, of the annexed pattern, so constructed as always to remain, 

 closed at the points except when subjected to pressure. With forceps of thia 

 kind, the vessels in question may be taken up and disengaged in an instant, 

 without the intervention of the right hand. The forceps may be laid down also,, 

 whilst the vessels are red hot, without risk of the latter coming in contact witls 

 the table. 



e.J.c. del. 



