Intelligence mid Miscellaneous Articles. 307 



those of Mr. MacMullen. I shall not notice all Mr. Johnston's 

 statements ; the correctness of the first two I admit ; the third and 

 fourth are as destitute of accuracy as the fifth, which is as follows: 

 — " I threw down a pure carbonate from a pure muriate of manga- 

 nese, obtained by Faraday's process. This was dried and partially 

 decomposed by heating in an oven ; with diluted sulphuric acid it 

 gave also the smell of chlorine." 



M From these experiments," continues Mr. Johnston, " we may 

 legitimately conclude, first, that Mr. MacMullen was correct as to 

 the fact of the emission of chlorine from the native oxide, which 

 Mr. Phillips has called in question, for it is given off by artificial 

 oxides, into which no trace of a muriate could possibly enter." 



If Mr. Johnston had read my remarks upon Mr. MacMullen's 

 paper, he would have found not that I called in question the fact of 

 the emission of chlorine from the native oxide, but on the contrary 

 that I admitted and explained it; nor can I discover the accuracy 

 of the reasoning by which it is attempted to be proved, that the na- 

 tive peroxide of manganese must yield chlorine, because it is given 

 off by the artificial peroxide, even admitting this to be a fact. 



I assert, however, and every chemist will readily admit the cor- 

 rectness of my statement, that pure carbonate of manganese does 

 not yield chlorine by the action of acids. I poured muriatic acid 

 upon perfectly white and moist carbonate of manganese ; no smell 

 of chlorine was perceptible, and litmus paper was reddened instead 

 of having its colour destroyed. 



When, however, carbonate of manganese is dried, a portion of it 

 is decomposed, oxygen being absorbed and carbonic acid evolved ; 

 and if muriatic acid is added to this mixture, chlorine is readily ob- 

 tained, mingled with carbonic acid : this, however, will not account 

 for the evolution of chlorine when sulphuric acid is employed to de- 

 compose the carbonate. But there are two modes of accounting 

 for its production : first, if the precipitate be not sufficiently washed 

 it will contain chloride of potassium or sodium, derived from the 

 union of the base of the precipitating alkali with the chlorine of the 

 muriate of manganese; or, which I have repeatedly found to be the 

 case, a submuriate of manganese is formed ; and sulphuric acid act- 

 ing upon a mixture of carbonate, per- or deut-oxide and submuriate 

 of manganese would readily occasion the evolution of chlorine for 

 the disengagement of which Mr. Johnston finds it so difficult to 

 account. R. P. 



BROWN OXIDE OF CHROMIUM. 



This compound may be formed by mixing a solution of chromate 

 of potash with protochloride of chromium, or by boiling chromic 

 acid with protoxide of chrome; when the brown oxide obtained is 

 digested with acetate of lead, chromate of lead and acetate of the 

 protoxide of chrome are formed. Potash also converts it into 

 chromic acid, and green oxide of chrome. Arsenic acid, carefully 

 added, produces arseniate of chrome and chromic acid. 



The brown precipitate produced by mixing chromate of potash 

 and chloride of chromium, is decomposed by being repeatedly washed 



2 R2 



