1826.] in Minerals by the Blowpipe. 133 



only discovered at the close of a tedious chemical process. 

 Secondly, we obtain a method of ascertaining the presence or 

 absence of hthia in other minerals. I have examined a consi- 

 derable number of substances with this view, but have not 

 hitherto been successful. 



As several of the salts of strontia and lime possess the 

 property 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 mistak- 

 ing 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 par- 

 ticle of strontianite, powdered and made into a paste as usual, 

 is exposed on platinum wire to the blowpipe flame, it communi- 

 cates a yellowish colour to it. By continuing the blast for a 

 little time, phosphorescence commences, 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 

 phosphorescence sets in, and then the assay gives a strong 

 brown stain to moistened turmeric paper. The property of 

 strontianite in colouring flame is lessened by mixing it with the 

 flux. When celestine is exposed in like manner, no redness 

 appears at first ; but if a strong heat be kept up for a minute or 

 two, the salt is decomposed, phosphorescence commences, fol- 

 lowed by a red hue, and the assay is found to be alkaline. This 

 change is facihtated bv mixing the celestine with the flux of 

 bisulphate of potash and fluor spar. Complete fusion then 

 occurs, though without the least trace of a red colour; but on 

 continuing the blast, the assay gradually becomes solid, and 

 then the strontia is speedily reduced to the caustic state. I 

 have been thus particular in describing these appearances, 

 because they aftord us a useful test to distinguish the native 

 salts of strontia from those of baryta ; while they cannot be 

 confounded with the effects produced by lithia. 



The carbonate and sulphate of lime give rise to the same 

 phenomena, though the effect is less distinct ; and the colour, 

 as in the case of strontia, does not appear till the lime is reduced 

 to its caustic condition. I have examined a considerable num- 

 ber of siliceous minerals containing lime, in some of which, as 

 datolite and apophyllite, that earth is present in a large propor- 

 tion ; but none of them, whether alone or with flux, give a red 

 colour to the flame of the blowpipe. It is probable, from this 

 fact, that strontia, did it chance to occur in a siliceous mineral, 

 would likewise be inert; or if it did redden the flame, it would 

 be under circumstances which would distinguish it from the 

 action of lithia. For the strontia would be converted into a 



