Lithia in Minerals by the Blowpipe. 115 



ture acts on spodumene in the same way as the preceding, 

 and, doubtless, from the same cause. It communicates a 

 pale-blueish 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 mis- 

 taken 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 

 recommended, it affords abundant evidence of the presence of 

 lithia. Indeed, from the great affinity of fluoric acid for sili- 

 ca, it is obvious that no siliceous mineral can withstand its 

 action ; and there can be almost as little doubt that the pre- 

 sence of lithia 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 me- 

 thod of ascertaining the presence of lithia in mineral bodies, is 

 twofold. In the first 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 only discovered at the close of a tedious chemi- 

 cal process. Secondly, we obtain a method of ascertaining 

 the presence or absence of lithia in other minerals. I have 

 examined a considerable number of substances with this view, 

 but have not hitherto been successful. 



As several of the salts of strontia and lime possess the pro- 

 perty of communicating a red colour to flame, it is natural to 

 inquire, whether the presence of those earths in a mineral 

 might not give rise to fallacy ; and I have, accordingly, 

 studied the subject with care. Though there is little danger 

 of mistaking a native carbonate or sulphate of strontia for a 

 siliceous mineral containing lithia, it may not be superfluous 

 to mention the characters they exhibit before the blowpipe. 

 When a particle of strontianite, powdered and made into a 

 paste as usual, is exposed on platinum wire to the blow- 

 pipe flame, it communicates a yellowish colour to it. By con- 

 tinuing the blast for a little time, phosphorescence commen- 

 ces, and soon afterwards a red colour makes its appearance. 

 This latter effect depends on the expulsion of carbonic acid ; 

 for no redness is visible till the phosphorc-sccnee sets in, and 



