132 Dr. Turner on the Means of detecting Lithia [FfiB. 



From the action of fluor spar on spodumene, I was desirous 

 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 bisulphate of potash in atomic 

 proportion ; that is, one of the former to about four and a half 

 of the lattei. When this flux was mixed with an equal quantity 

 of spodumene, the effect was, if any thing, still greater than in 

 the previous instance. Both these fluxes appear to act by giv- 

 ing 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 requires a stronger heat before yielding 

 fluoric acid, and hence the disengagement takes place under the 

 most favourable circumstances. 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, owing to 

 the presence of potash, which cannot be mistaken for the action 

 of lithia by any one who compares both effects together, as I 

 shall immediately demonstrate to the Society. But in case any 

 doubt should arise, it is easy to avoid the difficulty 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 mixture acts on spodumene in the 

 same way as the preceding, and doubtless from the same cause. 

 It communicates a pale bluish-green colour to the flame at the 

 first moment, and before fusion occurs — a property possessed 

 by several of the salts of ammonia; but there is no appearance 

 that can be mistaken for the red colour of lithia. 



When petalite is heated alone before the blowpipe, it yields 

 no trace of redness ; but if subjected to the process just recom- 

 mended, it affords abundant evidence of the presence of lithia. 

 Indeed, from the great affinity of fluoric acid for silica, it is 

 obvious that no siliceous mineral can withstand its action ; and 

 there can be almost as httle doubt that the presence of Hthia 

 may be detected in any such compound by the process which is 

 so successful with spodumene and petalite. 



The advantage of possessing an easy and expeditious method 

 of ascertaining the presence of lithia in mineral bodies is two- 

 fold. In the lirst place, the mineralogist and chemist possesses 

 a test for spodumene and petalite, from the want of which other 

 minerals have sometimes been mistaken for them, and the error 



