24 Dr. Turner's Chemical Examination 



Regarding 22 as the equivalent of carbonic acid, we have the 



following proportions :— As 34*72 : 56*853 : : 22 : 36*024. 



According to this analysis, 36 may be safely adopted as the 

 combining proportion of the protoxide of manganese; and 

 presuming the elements of this compound to be in the ratio of 

 one equivalent of oxygen to one equivalent of metallic man- 

 ganese, 28 will be the equivalent of the latter. This result, 

 with respect to the acid and base, corresponds exactly with 

 the analysis of Dr. Thomson, as mentioned in his First Prin- 

 ciples of Chemistry, vol. ii. p. 350. It differs considerably 

 from the proportions stated by Dr. Forchhammer. (Annals 

 of Philosophy, N. S. vol. i. p. 54.) According to this chemist, 

 33*05 parts of carbonic acid combine with 51*755 parts of the 

 protoxide of manganese, a proportion which would fix 34*45 

 instead of 36 as the equivalent of the protoxide. This esti- 

 mate is certainly erroneous ; and Dr. Forchhammer appears 

 to have fallen into the mistake by supposing that the carbonate 

 of manganese is converted by a red heat into the deutoxide, 

 whereas according to my experiments the red oxide chiefly is 

 then generated. 



It appears doubtful whether the water found by analysis in 

 the carbonate, after being dried in vacuo with sulphuric acid, 

 is mechanically retained by it or is in a state of chemical union. 

 As the proportion is not atomic, it is probable that the car- 

 bonate is really anhydrous. If the ratio were as 58 to 4*5 in- 

 stead of 5*337, the salt might be regarded as a compound of 

 two equivalents of the carbonate of manganese and one equi- 

 valent of water. 



Composition of the Sulphate of Manganese. — The most re- 

 cent analyses of the sulphate of manganese are by Dr. Forch- 

 hammer and Dr. Thomson, described in the works already 

 quoted. Dr. Forchhammer precipitated the acid of a known 

 quantity of the neutral sulphate of manganese by the nitrate 

 of baryta, and inferred from the weight of the precipitate, that 

 100 parts of the sulphate of manganese are composed of 54*378 

 parts of sulphuric acid and 45*622 of the protoxide. Accord- 

 ing to this analysis, the atomic weight of the protoxide is 

 33'56, a number which is surely very far from the truth, and 

 is inconsistent with the equivalent of that oxide derived from 

 Dr. Forchhammer\s own analysis of the carbonate. 



Dr. Thomson analysed the sulphate of manganese by mix- 

 ing that salt in atomic proportion with the muriate of baryta, 

 and found, that, after the insoluble precipitate had sub- 

 sided, no trace of sulphuric acid or baryta could be found in 

 the solution. From this experiment he infers that 36 is the 



equivalent 



