382 Notices respecting Nexu Booh. 



Dr. Thomson has also mentioned that if the peroxide be exposed 

 to too high a temperature, it loses more oxygen, — not indeed suffi- 

 cient to convert it into protoxide, but there is obtained a compound 

 of 1 atom of protoxide with 2 atoms of deutoxide. Now Dr. Tur- 

 ner says, that by the action of sulphuric acid " the peroxide loses a 

 whole proportion of oxygen, and is converted into protoxide, which 

 unites with the acid, forming a sulphate of the protoxide of man- 

 ganese." This statement is at variance with both Dr. Thomson's 

 and also with the results of our experiments ; for we find that ^'t 

 or 1 atom of peroxide of manganese yield 4*2 of oxygen, which is 

 so much nearer 4 than 8, that there is no question but that the 

 deutoxide and not the protoxide is obtained by the action of sul- 

 phuric acid ; that this is the case is further proved by the deep red 

 colour of the solution of the sulphate, and by its losing that colour, 

 as stated by Dr. Thomson, when mixed with sulphurous or nitrous 

 acid. 



In describing the properties of oxygen gas, the author states that 

 it does " not evince a disposition to unite with acids or alkalies." 

 Perhaps not with them, as such, and yet it combines with sulphurous, 

 nitrous, and other acids, and with potash, soda, and other alkalies ; 

 and the compounds which it forms are not divided by chemists into 

 acids and oxides only, but into acids, oxides, and alkalies. Hydro- 

 gen is the second elementary body in Dr. Turner's arrangement. 

 We do not deny, but we most certainly doubt, the production of 

 carbonic acid when iron is dissolved in dilute sulphuric acid : the 

 metal unquestionably contains charcoal, — but v/hence proceeds the 

 oxygen necessary to its conversion into carbonic acid ? This 

 chapter contains but few other passages which call for obser- 

 vation, excepting the assertion that zinc cannot decompose water 

 at common temperatures is contradicted both by Davy's experience 

 and our own. It takes place with great slowness, but still it 

 actually does occur. We do not find any thing material to arrest 

 our progress till we arrive at Nitric Acid (p. 195) ; and here in- 

 tending to resume pur remarks on this subject, we shall first quote 

 Dr. Turner's statement, that *' there are two substantial reasons for 

 using more than one proportion of sulphuric acid to one of nitre. 

 The first is, that nitre cannot be wholly decomposed by a quantity 

 of sulphuric acid, which is merely sufficient to form a neutral sul- 

 phate. Owing to the tendency of potassa to unite with two propor- 

 tions of that acid, the product would contain a portion of bisulphate 

 and of undecomposed nitre." This part of the subject we have al- 

 ready disposed of; but by referring to Wollaston's admirable paper 

 on Chemical Equivalents, Dr. Turner will find the true reason for 

 employing 2 atoms of oil of vitriol for decomposing 1 atom of 

 nitre : it is, that there may be sufficient water for condensing the 

 nitric acid; for while 1 atom of sulphuric acid = 40 is condensed 

 by 9 = 1 atom of water, 1 atom of nitric acid = 54, requires 2 

 atoms of water = 18 for its condensation; the formation of the 

 bisulphate of potash is a consequence merely of employing as much 

 sulphuric acid as contains the requisite quantity of water to con- 

 dense the nitric acid. The other reason for employing 2 atoms 



of 



