ON SOME BLOWPIPE-REACTIONS. 255 



error, as the presence of iodine is revealed — ^even if no violet-coloured 

 fumes be emitted — by tlie dark amethystine colour of the bead whilst 

 hot. 



VII.— ON THE DETECTION OF CAHBONATES IN BLOWPIPE 

 PRACTICE. 



A mineral substance of non-metallic aspect, in nine cases out of 

 ten, will be either a silicate, sulphate, phosphate, borate, carbonate, 

 fluoride, or chloride color : more especially if the streak be uncoloured 

 or merely exhibit some shade of green or blue, or if the substance 

 evolve no fumes when heated on charcoal. 



Simple fusion with phosphor-salt on a loop of platinum wire 

 serves at once to distinguish a silicate from any of the other bodies 

 enumerated above, as, whilst the silicate is but slowly attacked, 

 these other bodies are readily and rapidly dissolved. Among the 

 latter, again, the carbonates are distinguished without risk of error by 

 the marked effervescence which they produce in the bead by the 

 evolution of carbonic acid during fusion — the phosphates, sulphates, 

 &c., dissolving quietly. The reaction is quite as distinctive as that 

 produced by the application of an ordinary acid ; but, of course, it 

 may arise in both cases not only from a carbonate proper, but from 

 the presence of intermixed calcite or other carbonate in a silicate or 

 other body. It was by its use, upwards of twenty years ago, that 

 the writer detected the presence of carbonate of lime in certain 

 specimens of Wernerifce (the " Wilsonite " variety), portions of which 

 had previously been analyzed without the impurity having been 

 discovered. It need scarcely be stated that the test-substance must 

 be added to the phosphor-salt, on the platinum loop, only a,fter the 

 quiet fusion of the flux into a transparent glass. The reaction is, of 

 course, manifested equally well with borax.* 



VIII.— ON THE USELESSNESS OF TURNER'S FLUX AS APPLIED 

 TO THE DETECTION OF BORACIC ACID. 



Many years ago — about 1827 or 1828 — Turner proposed, in 

 examining a body for the presence of boracic acid, to mix the test- 

 substance with bisulphate of potash and fluor-spar (in the proportions 



* It is singular that this very marked and useful reaction should not have lieen alluded to in 

 any of the standard treatises on Blowpipe Practice. The only work known to the writer in. 

 which a passing reference is made to it, is that of Hirschwald ("Lothrohr-Tabellen"), published 

 in 1875. The present writer called attention to it in ISYl. 



