462 Capt. W. A. Ross on Pyrology, or Fire Analysis. [June 20, 



alumina and silica in various ways, one of which is referred to in paragragh 

 18, which occupied the writer some years, the following plan, which ought 

 from its simplicity to have suggested itself at first, has been followed with 

 apparent success. 



Nearly every oxide or substance is more soluble pyrologically in P than 

 alumina and silica, while alumina is far more soluble than silica is. The 

 " alkaline earths " are rapidly dissolved ; and lime especially is not only 

 dissolved, but forms a salt, referred to in paragraph 39, which will dissolve 

 almost any thing but silica*. 



56. It has been ascertained that alumina will dissolve to the extent of 

 20 per cent., and silica to that of only 6 per cent, in a P bead ; and this result 

 is not materially modified by lime. After those amounts respectively have 

 been added, the undissolved alumina appears as white roundish fragments, 

 like pieces of fat, the silica as a semitransparent mass like melting snow, so 

 that they are thus distinguished without difficulty even in presence of lime 

 or the alkaline earths. 



Six per cent, is therefore taken as the standard of silica in quantitative 

 calculations ; but as 20, that of alumina, is inconveniently large, it is better 

 to employ as the flux a P bead half saturated with 10 per cent, of pure 

 alumina, and to make 10 the standard of that "earth." 



57. A P glass saturated with silicic acid still dissolves a little alumina, 

 but the converse is not the case ; it is best, therefore, to test qualitatively 

 for either earth with a P glass saturated with alumina. 



Boric Acid (Symbol P). 



58. Plattner and succeeding writers on the "blowpipe" made use of this 

 substance for the purpose of separating metallic lead from copper in an 

 alloy of the two by oxidizing the former, and therefore as a means of affi- 

 nage of the latter metal "f. In this operation, B appears to absorb litharge 

 precisely as bone-ash does in cupellation ; but it acts at the same time as a 

 kind of shield to protect the copper from oxidation. 



59. Berzelius employed B as a test of phosphoric acid in phosphates by 

 the insertion through the mass of a piece of pure iron wire, which is cor- 

 roded and fused if the phosphoric acid exists over 5 per cent. ; but this reac- 

 tion, to be effectual, presupposes the perfect solution of the substance contain- 

 ing the phosphate in B, which, as will be seen, can be effected with very 

 few oxides indeed. 



60. In fact it is precisely the insolubility of almost all substances but the 

 alkalies in boric acid which gives it the extraordinary value it undoubtedly 

 possesses as an agent of separation ; and the following few examples will 

 not only clearly demonstrate this fact to the impartial chemist, but show 



* Borax dissolves silica pyrologically more completely than any known flux. The 

 writer found that phosphoric and nitric acids, combined in about equal proportion, at- 

 tacked and broke up the Berlin saucers in which they were boiled. 



t Vide Plattner's " Probirkunst" &c, edition of 1865. 



