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



The principal points which require attention, to ensure success in 

 this process, are, to have the materials in the state of very fine powder, 

 and the moist compositions of a proper degree of consistency. If they 

 are too soft, the support will not quit the mould without losing its 

 form. If too dry, the particles of the support will not cohere. The 

 proper state is found after a few trials. It is most convenient to 

 begin by making the mixture too soft, and then drying it slowly till 

 found to be hard enough to work easily. The composition is rolled 

 into little balls of the size before mentioned by means of the fingers. 

 The moulds should be kept clean, and the forming parts of the pestle 

 B and the ring D should be oiled. The best way to clean the hole in 

 the mould D is by means of a long conical cork, rasped to a rough 

 surface and oiled. The point of the pestle A must not be oiled, 

 because grease prevents the adhesion of the combustible portion of the 

 support to its clay base. 



When the support is taken from the mould it is put on a hot plate 

 or a sand bath to dry, after which, the rough edges are taken off by a 

 rasp. It is then ready for use. The bottoms of the supports for 

 reductions are painted with red ochre mixed with rice paste, to dis- 

 tinguish them from the other kind. The size I have fixed upon is as 

 follows : — height ^ inch, diameter at the top -J inch, at the bottom f 

 inch. The weight is about 16 grains, consisting of 10 grains of clay 

 crucible, and 6 grains of combustible matter. I have tried several 

 other sizes, but find this to be the most generally convenient. Never- 

 theless, a higher temperature can be produced upon a smaller support, 

 and I find that large masses of charcoal are not essential, since many 

 blowpipe experiments can be finished during the combustion of only 

 two grains of charcoal. 



Before I proceed to explain the mode of using these supports, I 

 must describe the handle by means of which they are to be held in 

 the blowpipe flame. This handle consists of an iron wire, 3J inches 

 long and -^^ inch in diameter, one end of which is bent into a ring 

 about f inch in diameter, while an inch of the other end is forced 

 through a round cork 1 inch long and i inch in diameter, as repre- 

 sented by figs, hy c. The operator fixes the support in the ring of this 

 wire, and holds it by the cork handle, which is intended, not so much 

 to protect the fingers from heat, as to provide the power of varying the 

 position of the support in the flame, as the progress of an ignition may 

 require. 



I shall now describe one or two experiments which show the method 

 of using these supports. 



1). The surface of one of the Supports for Fusions is heated before 

 the blowpipe till it is red hot. If then removed from the blowpipe 

 flame, the support continues to burn, like an ordinary pastile, till it 

 is consumed down to the clay. In this respect, the support has a 

 superiority over ordinary charcoal, which soon ceases to burn when 



