212 ON THE ASSAYING OF COALS BY THE BLOWPIPE. 



methods of ascertaining the nature and amount of ash, pyrites, &c., see 

 under § 3 below. 



§ 2. INSTRUMENTS AND APPLIANCES. 



The instruments, &c., employed in these examinations are the 

 following : a blowpipe, blowpipe-lamp, and small spirit-lamp of the 

 ordinary construction ; together with the usual accessory instruments 

 and re-agents which always accompany the blowpipe. These require 

 no special description. The blowpipe may be of any form, but for the 

 purpose of heating small platinum vessels in these experiments, it is 

 convenient (although not absolutely necessary) to add to it an extra 

 jet with an orifice rather larger than usual. The blowpipe-lamp should 

 also be furnished with a broad wick-holder of the pat- 

 tern recommended by Plattner (fig. 1), in place of the 

 flat wick-holders formerly in use. In heating cruci- 

 bles it- is advisable to turn the wick-holder so as to 

 make the upper surface slope towards the right hand 

 instead of towards the left, the flame being then 

 directed upwards, against and around the bottom of 

 the crucible. Or, to avoid the trouble of changing the position of the 

 wick-holder, the operator may turn the lamp itself, placing it with its 

 fore part away from him. 



In addition to the above, the folio-wing appliances, of more special 

 use, are also needed: — (1). Two platinum capsules as thin as they can 

 be obtained. One about half an inch in diameter, provided with a 

 small ear or handle ; and the other of somewhat smaller dimensions, 

 and without any projecting ear. The smaller capsule, reversed, fits 

 into the larger one, the two then constituting a closed vessel. Those 

 which I employ, weigh together less than 42 grains. (2). A small 

 platinum crucible with a lid. I make use of two small but deep plati- 

 num spoons; one with, and the other without a handle. The latter 

 must be the larger of the two. Its edges must be bent slightly inwards 

 so as to allow it when reversed to be fitted closely over the smaller 

 spoon, and thus to constitute a lid. The long handle of the spoon 

 crucible should be bent as shewn in figure 2. The ob- ^ 



ject of this is to enable the crucible to retain an upright 

 position when placed on the pan of the balance. The 

 figure shews the exact size and form of the crucible 

 employed by me. Its weight is a little under 36 grs. 

 In some spoons a slight notch must be cut in the lid to admit the 

 passing of the handle. (3). A pair of steel tongs or forceps to hold 



