162 Mr. Griffin on a Charcoal Support for Blowpipe Experiments. 



it, and all its elements be driven off except the copper, which is 

 finally obtained in a single metallic bead. A globule of metallic tin, 

 an eighth of an inch in diameter, can be kept boiling upon a support 

 without being converted into oxide. A crystal of quartz can be fused 

 into soda glass. Flint glass can be melted with metallic oxides, in 

 such quantities as to form beads of enamel or coloured glass the sixth 

 of an inch in diameter. And these effects are producible upon a sup- 

 port of th€J weight of only 16 grains, and during the combustion of 

 perhaps not more than 3 or 4 grains of charcoal. Indeed, many 

 striking results are produced by a combustion of only 2 grains of 

 charcoal, but then this combustion is effected under very favourable 

 circumstances, where very little more charcoal is heated than is 

 intended to be burnt, and where no more is burnt than is required to 

 produce the intended effect. 



This power of restricting the consumption of charcoal in such 

 experiments, is a merit which will render these composition supports 

 acceptable to travelling mineralogists. Berzelius laments the diffi- 

 culty of procuring good charcoal when travelling, even in the well- 

 wooded regions of the north, and this difficulty, and the consequent 

 necessity of carrying about a quantity of charcoal, all travelling 

 analysts must find an annoyance. But as the supports which I have 

 described, require for each only a cube of \ of an inch of charcoal, it 

 follows that a sufficiency of either mixture, for no less than 500 experi- 

 ments, may be carried in a square tin box measuring only two inches 

 on each side. Moreover, the incombustible portion of the supports 

 can be pounded down and remoulded any number of times, so that 

 only a very small quantity of clay is requisite. 



3). The last blowpipe experiment to which I shall now allude is 

 cupellation, the performance of which before the blowpipe, is consi- 

 derably facilitated by the apparatus described in this notice. When 

 a cupellation is to be effected, a clay crucible is made in the mould D, 

 by means of the pestle A, in the manner already described, and into 

 this crucible a quantity of moistened bone ashes is pressed by the 

 pestle B, so as to make a cupel similar in form to a charcoal support, 

 fig. E, but consisting of bone ashes. This cupel being mounted upon 

 the wire handle, shown by figs. &, c, is ready for use. A much higher 

 temperature can be raised upon such a cupel than upon the same 

 quantity of bone ashes placed, as usual, in a hole cut in a large piece 

 of common charcoal. 



I have now only to state my reasons for choosing rice as an ingre- 

 dient of these pastile supports. They are, that rice paste is a strong, 

 cheap, and convenient agglutinant ; that when heated before the blow- 

 pipe it melts and binds the charcoal powder well together; that when 

 decomposed, its charcoal is very difficult of incineration ; and that its 

 ashes are neither more abundant nor more troublesome than those of 

 wood charcoal that forms the mass of the support. These properties 



