114 Dr Turner on the Means of Detecting 



culiar colour to appear from the mere circumstance of becom- 

 ing fluid. Spodumene, for example, can be made to fuse by 

 the addition of the carbonate of soda or potash, but no red- 

 ness occurs. Fusion is rendered still more perfect by the ac- 

 tion of boracic acid, or the phosphate of soda and ammonia, 

 but without a trace of redness being visible. 



These facts prove that a certain chemical condition of a body 

 is necessary, in order that it should produce its effect on flame, 

 and that this circumstance has a greater influence than form. 



From the action of fluor-spar on spodumene, I was de- 

 sirous of trying the effect of free fluoric acid on that mineral. 

 It was accordingly mixed with some of the bifluate of potash, 

 and a little of the mixture, made into a paste with a drop of 

 water, was exposed by means of platinum wire to the flame of 

 the blowpipe. It fused very easily, and emitted a brilliant 

 red flame, far more distinct than that occasioned by the fluate 

 of lime. To vary the experiment still further, a mixture was 

 made, composed of fluate of lime and bi-sulphate of potash in 

 atomic proportion ; that is, one part of the former to about 

 four and a half of the latter. When this flux was mixed with 

 an equal quantity of powdered spodumene, the effect was, if 

 any thing, still greater than in the previous instance. Both 

 these fluxes appear to act by giving out fluoric acid at a high 

 temperature, which destroys the composition of the mineral 

 by combining with the silica and setting the lithia free. The 

 latter flux is more effectual than the former, because it re- 

 quires a stronger heat before yielding fluoric acid, and hence 

 the disengagement takes place under the most favourable cir- 

 cumstances. It should therefore be preferred in practice. 



In performing these experiments, it is important to keep in 

 view the action of the flux itself on flame. Those that have 

 been just recommended communicate a faint lilac colour, ow- 

 ing to the presence of potash, which cannot be mistaken for 

 the action of lithia by any one who compares both effects to- 

 gether, as I shall immediately demonstrate to the society. 

 But in case any doubt should arise, it is easy to avoid the dif- 

 ficulty by employing a flux that contains no potash. Such a 

 one may be made by mixing one part of the fluate of lime 

 with one and a half of the sulphate of ammonia. This mix- 



II 



