32 Dr. Turner's Chemical Examination 



moist state for twenty-four hours, and then heated in an open 

 vessel to a moderate red heat, which was insufficient to de- 

 compose the deutoxide, lost only 0*218 per cent by subsequent 

 exposure to a white heat. The quantity of deutoxide present, 

 therefore, must have been very minute. The anhydrous prot- 

 oxide, as already mentioned, always yields the pure red oxide 

 when heated to redness in the open air. The carbonate, also, 

 in similar circumstances, is converted into a red oxide con- 

 taining but a very small proportion of the deutoxide. It will 

 appear from these experiments that it is unsafe in analyses to 

 heat the precipitated protoxide or carbonate to redness, and 

 consider the product as the deutoxide; a practice which is 

 calculated to lead analytical chemists into considerable errors, 

 and indeed has actually done so. If it is wished to procure 

 the deutoxide, the precipitate should be moistened with nitric 

 acid, and then exposed to heat. 



I have endeavoured to ascertain the composition of the red 

 oxide by several methods. The first is by the combined agency 

 of heat and hydrogen gas. In the first experiments 100 parts 

 of pure red oxide, in being thus converted into the protoxide, 

 lost 6*802 and 6*817 parts of oxygen; but as the resulting 

 green oxide, when put into dilute sulphuric acid, w r as found 

 to contain a little red oxide, the loss in oxygen must be rather 

 below the truth. To avoid this error I exposed 44*256 grains 

 of red oxide to hydrogen gas and a white heat for the space 

 of one hour, when the loss amounted to 3*153 grains on 7*125 

 per cent. 



Judging by the increase in weight which the protoxide ac- 

 quires when heated in the open air, 100 parts of the red oxide 

 consist of 93*05 parts of protoxide and 6*95 of oxygen. Ac- 

 cording to a similar experiment made by Arfwedson, the red 

 oxide is composed of 93*153 protoxide and 6*847 parts of 

 oxygen. 



In an analysis already described, the carbonate of manga- 

 nese was found to contain 56*853 per cent of the protoxide of 

 manganese. When 100 parts of the same carbonate are ex- 

 posed to air and a white heat, 61*18 parts of red oxide are 

 obtained. From these data it may easily be calculated that 

 the red oxide consists of 92*927 parts of protoxide, and 7*073 

 of oxygen. 



As a mean of the numbers afforded by these three methods, 

 it follows that the red oxide is composed of 92*951 parts of the 

 green oxide and 7*049 of oxygen, or of 72*291 parts of metallic 

 manganese and 27*709 of oxygen. According to M. Berthier*, 



* Ann. de Chimie et de Physique, torn. xx. 



who 



