256 ON SOME BLOWPIPE-REACTIONS. 



of 4 1 parts of the former to 1 part of tlie latter), and to expose the 

 mixture on a clean platinum wire to the point of the blowpipe 

 flame. Fluo-boric acid is thus produced ; and by its volatilization, a 

 momentary green colour is imparted to the edge of the flame^ 

 Merlet recommends the employment of 3 or 4 parts of this flux to 

 1 part of the substance imder examination. This test is much 

 quoted in blowpipe books and works on chemical analysis generally; 

 but it is altogether superfluous. With borate of soda it fails entirely, 

 or yields very unsatisfactory results; and although it answers for 

 most other borates and for boro-silicates, it is uselessly applied to 

 them, because these bodies colour the flame equally well, per se, 

 Berzelius seems strangely to have overlooked the coloration of the 

 flame as produced by many substances under blowpipe treatment. 

 In his work on the blowpipe, for example, he fails to notice the 

 character in describing the reactions of lepidolite, sulphate of baryta, 

 datolite, triphylline, and other minerals, which exhibit it most "dis- 

 tinctly. Under axinite, moreover, he has the following statement : 

 " Turner asserts that a flame tinged green by boracic acid is obtained 

 by the aid of sulphate of ammonia (or bisulphate of potash) and 

 fluor spar." This " assertion " is true enough ; but all specimens of 

 axinite colour the flame green, per se. The uselessness of the flux 

 was pointed out, I find, by Buzengeiger as long ago as 1829. In 

 the Annales des Mines for that year (tome v., p. 36), he states: " J'ai 

 essaye, pour reconnaitre la presence de I'acide borique, d'employer le 

 flux indique par M. Turner, mais ces tentatives ne m'ont pas reussi, 

 probablement par defaut d'habitude. Quoi qui en soit, tous les 

 mineraux que M. Turner a vu colorer la flamme en vert en les melant 

 avec son flux, m'ont donne la meme reaction en les introduisant avec 

 quelque soin dans la flamme bleue, sans les melanger avec aucun ■ 

 reactif." Buzengeiger, whose name does not seem to be quoted in 

 any blowpipe work, appears to have first proposed the sloping blow- 

 pipe-wick, long before it was adopted by Plattner ; and he noticed, 

 at the same early date, that the crimson coloration of the strontium-^ 

 flame was entirely obliterated by the presence of barytic compounds. 



IX.— ON THE COMPORTMENT OF CERTAIN ALLOYS UNDER THE 

 ACTION OF THE BLOWPIPE. 



In examining these reactions, about equal portions of the metals 

 (forming the alloy) may be placed together, on. charcoal, and subjected 

 to the action of a reducing flame. 



