373 Memoir upon Zircon. 



2d, by Ujj not being coloured byhydrosulphuric acid ; 3d, by the hy- 

 drosulphate of ammonia producing with it a perfectly white preci- 

 pitate. M. Chevreul took the mass which had been washed with 

 the hydrochloric acid ; he diluted it in water, filtered the mix- 

 ture, and precipitated the pure zircon by ammonia. The hy- 

 drate which he obtained he calcined in a glass capsule. This 

 process, it will be observed, rests principally on this circum- 

 starice ; that a quantity of concentrated hydrochloric acid insuf- 

 ficient to dissolve a certain quantity of hydrochlorate of zircon, 

 suffices, on the contrary, to dissolve the hydrochlorates of iron 

 and copper intermixed with the latter. 



M. Chevreul afterwards subjected the zircon and the peroxide 

 of titanium to a comparative examination. 



The hydrated zircon dried in the air is soluble in hydrochloric 

 acid. This combination crystallizes in small satin-like needles 

 of the purest white. The excess of acid may be expelled from 

 the hydrochlorate by evaporating to dryness : on rewatering the 

 residue, but very little zircon is separated, especially if the solu- 

 tion which was evaporated was concentrated : on again treating 

 it with hydrochloric acid, the process ends by redissolving it en- 

 tirely, if the evaporation has not been pushed too far. 



The hydrochlorate of titanium takes a yellow colour when a 

 concentrated solution of it is evaporated to dryness : a greater 

 quantity of it is decomposed than is the case with hydrochlorate 

 of zircon when evaporated ; and when the acid is added to the 

 residue, it has not the effect of redissolving it. But what most 

 'distinguishes this hydrochlorate from the preceding is, that on 

 joining three parts of water to one part of a solution of cacli 

 "hydrochlorate, and subjecting the two litjuors to the action of 

 heat, that of titanium allows a great deal of oxide or subhydro- 

 chlorate to precipitate even before ebullition ; while that of zir- 

 con may be evaporated to dryness without yielding any deposit. 



The hydrochlorate of zircon steeped in water is not decom- 

 posed, even after a lapse of many months ; that of titanium si- 

 Tiiilarly treated becomes milky, though the decomposition does 

 not take place at the very moment when the water is added. 



The hydrochlorate of zircon is precipitated of a dun yellow co- 

 lour by nut galls : if the solution is concentrated, the gelatinour 

 }>rccipitatc retains ail the liquor in its particles. The hydro- 

 chlorate of titanium presents, it is known, this latter phaenoine- 

 non ; but the precipitate is of a very lively orange red. 



The hydrochlorate of zircon is precipitated of a canary yellow 

 hy an excess of prussiate of potash; that of titanium, on the 

 contrary, is precipitated of a brownish red. M. Chevreul ha'* 

 observed that the two jjrecipitatcs were soluble in an excess ot 

 pruasiate of potash; that in certain circumstances the prussrare 

 of rircon was ahnost colourless ; and that it became yellow by 



an 



