On the Existence of Titanic Acid in Hessian Crucibles. 113 



in the directions of the axes, and of the three lines o A re- 

 spectively, will be 



d^ dxi d ds" d8^ d^ 



dt dt dt dt ~dt dt' 



and, we have also 



-@)%(S)%d-i)'-(^y-(S')"Mir^)' 



(41.) 

 [To be continued.] 



XVIII. On the Existence of Titanic Acid in Hessian Crucibles, 

 By Mr. R. H. Brett and Mr. Golding Bird. 



To the Editors of the Philosophical Magazine and Journal, 



Gentlemen, 



Tjy HILE repeating some experiments lately published on 

 ^ * the presence of titanium in organic matter, especially in 

 the renal capsules*, we observed that when an alkaline car- 

 bonate was exposed to heat in Hessian crucibles, a fused mass 

 was obtained, which was yellow while hot, but white and opake 

 when cold; on dissolving this fused mass in dilute hydro- 

 chloric acid and mixing the solution with hydrosulphuret of 

 ammonia, a deep olive green precipitate was obtained, which, 

 when dried and ignited, yielded a white powder, insoluble in 

 the dilute acids. These reactions so exactly resembling those 

 yielded by titaniferous substances, we were induced to sus- 

 pect the presence of titanium in the clay of which the crucibles 

 were formed. To determine this with accuracy we undertook 

 an analytical examination of the several varieties of Hessian 

 crucibles usually met with, and we found them all to consist 

 of (in variable proportions) silicic acid, titanic acid, alumina, 

 and peroxide of iron, with traces of magnesia and manga- 

 nese, and occasionally of lime. 



The quantity of titanic acid present differed considerably in 

 different specimens, in some not amounting to more than 3{ or 

 4f per cent., and in some few even to as much as 25 or 30 : it 

 was exceedingly rare to meet with so much as 25 per cent. ; 

 those crucibles that contained that quantity were generally 

 small, very thin, brittle, and studded with numerous black 

 semimetallic-looking specks. The quantity of peroxide of iron 

 present was small compared to that of titanic acid, and they 

 were by no means in the proportions in which they exist either 

 in the iserine or in the menachanite, to the presence of which 



* See our last vokime, p. 398. — Edit. 

 ThirdSeries. Vol. 6. No. 32. Feb. 1835. Q 



