26 Mineralogical Notices. 



gives the reactions of titanic acid, wiiilst from the sulphuric so- 

 lution (which gave a precipitate with sulphate of potash soluble 

 in an excess of the precipitant) yttria was obtained, in which 

 there might still possibly be zirconia and thorina. Arkansite 

 fuses with bisulphate of potash, according to Shephard, to a 

 yellowish mass, which, on ebullition with water, deposits a 

 heavy white precipitate; he found 67 per cent, of titanic acid, 

 and concluded from his experiments that the mineral was 

 titanate of yttria. 



Subsequently Shephard asserted the metallic acid to be 

 niobic acid, and gave as his opinion that the mineral was 

 niobate of yttria and thorina. He found the specific gravity 

 to be 3-854. 



Rammelsberg has recently examined this mineral; he found 

 the spec. grav. to be 3-892, 3-923, 3-949. 1-7205 grm. lost 

 on ignition 0-0045. After fusing the residue with bisulphate 

 of soda, the mass readily dissolved in water at a gentle heat, 

 the mineral consequently contains no tantalic, niobic or pelopic 

 acid. The solution mixed with some sulphuric acid deposited 

 on boiling 1*49 of a white powder, which proved to be pure 

 titanic acid, both before the blowpipe as well as on being 

 mixed with sugar and carbonized, and then heated in a cur- 

 rent of chlorine. Ammonia precipitated from the filtered so- 

 lution 0-2 1 7 of a white gelatinous substance, which also proved 

 to be pure titanic acid on being tested in the same manner. 

 By treating the precipitates with hydrofluoric acid, the mineral 

 was found to be free from silica ; on treating them with chlo- 

 rine, there was no production of the difficultly volatile chlo- 

 rides of yttrium, thorium, and zirconium. 



On igniting a quantity of the separated titanic acid with 

 carbonate of soda, 100 parts expelled 50*52 parts of carbonic 

 acid. Now, since titanic acid contains, according to the expe- 

 riments of Pierre, 38-86 per cent, of oxygen, and according to 

 those of H. Rose 39*71, 1 atom of titanic acid expels 1 atom 

 of carbonic acid. The error amounts only to 0-005 carbonic 

 acid, which is trifling considering the small quantity employed. 



In this treatment alone 94 per cent, of the weight of the 

 Arkansite had been obtained of pure titanic acid ; there re- 

 mained 0'06 grm., in which nothing else could be detected 

 with certainty. 



Rammelsberg then observes, in opposition to an earlier 

 statement of Breithaupt, that the crystalline form of Arkansite 

 is identical with that of Brookite*, although the secondary 



* The same conclusion had been previously ariived at by Prof. Miller 

 of Cambridge, see Phil. Mag. for July 1849, p. 75. 



