1 82 InteUigence and Miscellaneous Articles. 



it be more strongly lieated, incandescence then begins, and the oxide 

 becomes green. If however the oxide which has become black 

 be heated in a small retort, it will be observed that a great disengage- 

 ment of gas occurs both before and during ignition ; this gas is oxy- 

 gen, and the oxide becomes at the same time green. 



Hydrated oxide of chromium is completely converted by heat in 

 contact with air into peroxide, Cv, which at a low red heat is changed, 

 with incandescence, into oxide of chromium. I\I. Krviger finds the 

 peroxide to consist of 63* 7 metal and 3G'3 oxygen. 



This peroxide is a peculiar compound, and does not contain 

 chromic acid ; if it be mixed with chloride of sodium and the mixture 

 be treated with sulphuric acid, chlorine is given out without the for- 

 mation of any trace of the red chromate of chloride of chromium. 

 When it is boiled with hydrochloric acid, the peroxide yields chlorine, 

 and if heated with sulphuric acid it gives oxygen ; the best method 

 of making these experiments is to precipitate hydrate of oxide of 

 chromium from dilute solutions by ammonia. If the precipitation be 

 effected in a boiling solution, it is obtained in a more compact state, 

 which renders it but slightly soluble in diluted acids. 



If to a solution of bichromate of potash there be added a neutral 

 solution of sulphate of chromium and then ammonia, there is obtained 

 a brown precipitate, from which, as shown by M. Mons, all the sul- 

 phuric acid may be removed by very long washing ; there remains 

 only hydrate of oxide of chromium ; according to this chemist this 

 precipitate is not peroxide of chromium, but chromate of basic oxide 

 of chromium Cr + Cr. 



If however the brown precipitate be washed only until sulphuric 

 acid cannot be discovered in the filtered liquor, and then after drying 

 in the air it is treated with chloride of sodium and fuming sulphuric 

 acid, no chromate of oxide of chromium is disengaged, but merely 

 chlorine, proving that the precipitate is merely peroxide of chromium, 

 but unquestionably in the state of hydrate. 



It is not decomposed even by long treatment with water into 

 chromic acid and oxide of chromium. If peroxide of chromium ob- 

 tained in this manner be heated, it loses water, and is converted, bv 

 a stronger heat, into oxide, with the disengagement of oxygen and 

 with ignition. — Jonrn. de Pharm. et de Ch. December, 1844. 



PREPARATION OF FERRATE OF SODA AND OP BARYTE.S, &C. 



M. Fremy states that, after having formed ferrate of potash in the 

 mode described (Phil. Mag., January, p. 81), he endeavoured to pro- 

 cure ferrate of soda by the same means ; but he found that it was im- 

 possible to obtain ferrate of soda by acting upon iron by nitrate of 

 soda in a Hessian crucible, this nitrate appearing to be much more 

 fixed in this case than the nitrate of potash ; the former salt is de- 

 composed slowly, and the free soda attacks the crucible. 



Ferrate of soda was readily obtained in the moist way by passing 

 chlorine into concentrated soda containing suspended hydrate of 

 peroxide of iron. 



