80 REPORT— ] 869. 



ratus, and in this and other ways is so costly that its use has never extended 

 beyond a sing-le firm of manufacturers. 



Three years ago the author began to endeavour to work out the idea of decom- 

 posing by either lime or magnesia the chloride of manganese in the residual 

 liquors of the chlorine manufacture, and then blowing air through the resulting 

 mixture of hydrated protoxide of manganese with solution of chloride of calcium 

 or of chloride of magnesium, as the case might be. He took for granted that one- 

 half of the protoxide of manganese so treated was the largest proportion of it that 

 could thereby be converted into MnOj — in other words, that one could obtain only 

 sesquioxide lay this method ; but it was soon found that, when using lime to de- 

 compose the chloride of manganese, considerably more than half the protoxide 

 operated upon was frequently' converted into MnO,. It was found eventually that 

 more than half the protoxide was thus peroxidized only when more lime was used 

 than simply the quantity necessary to decompose the chloride of manganese, and 

 when what was treated with air was thus a mixture of protoxide of manganese and 

 lime; and it was also found that in all such cases there was a definite relation 

 between the quantity of lime associated with the protoxide of manganese and the 

 quantity of the protoxide, in excess of half, which became peroxidized. This led 

 to the discovery that whereas when protoxide of manganese by itself is treated 

 with air in the wet way one-half is the maximum proportion of it which can 

 thereby be converted into MnO^,, the association of a certain proportion of lime 

 with the protoxide so treated will enable the whole of it to become converted into 

 MnOj. It is to this fact, together with that of the much greater rapidity with 

 which protoxide of manganese can be peroxidized by treatment with air in the «-et 

 way when lime is present than when lime is not present, that the practical success 

 of the new method of manufacturing chlorine is mainly due. 



The action of lime in increasing the proportion of protoxide of manganese which 

 can be peroxidized by treatment with air in the wet way, evidently consists in the 

 lime substituting itself for that part of the protoxide which, when protoxide ©f 

 manaranese not having any other basic substance associated with it is treated with 

 air in the wet way, does not undergo peroxidation. It would seem that the pro- 

 duction of MnOj in the wet way, by direct combination between hydrated MnO 

 and atmospheiic oxygen, absolutely requires the presence of a base with which the 

 MnO^ can combine as it forms. "When protoxide of manganese, not having any 

 other basic substance associated with it, is treated with air in the wet way, a part 

 of the protoxide itself has to act as the required base ; and this is the reason why, 

 in that case, not more than half of the protoxide can become peroxidized, the other 

 half being required to combine, as MnO, with the half which becomes converted 

 into MnOj. When, however, the protoxide of manganese which is treated with 

 air in the wet way has lime associated with it, the MnO, which forms (or a part of 

 it, according to the proportion of lime present) combines witli CaO instead of with 

 MnO, thus leaving free to undergo peroxidation that part of the MnO which, but 

 for the presence of the CaO, this MnOo must have combined with, and which 

 would thus have got locked up in a state in which it would have been incapable of 

 being peroxidized, at least in the wet way and by air alone. Hence the presence 

 of enough lime to take the place of that half of the protoxide which, if no lime 

 were present, would have to go into combination as base, and also to supply enough 

 base for that half itself to combine with after undergoing peroxidation, will enable 

 the whole of the MnO operated upon to be raised to the state of MnO,. The 

 minimum quantity of lime which is enough for this purpose is an equivalent for 

 each equivalent of MnO operated upon, or the quantity necessary to supply an 

 equivalent of lime to all the JNInO, which can be produced by the peroxidation of 

 all the MnO. 



By treating with air, then, a mixture of protoxide of manganese and lime suspended 

 either in water or in solution of chloride of calcium, there is formed a compound 

 containing MnO, and OaO in the proportion of an equivalent of one to an equivalent 

 of the other. This compound may be regarded as sesquioxide of manganese, or 

 Mn^03, the MnO in which is replaced by CaO. The author calls it manganite of 

 calcium, and believes it to be a new compound. Gorgeu, in 1862, described a com- 

 pound which he called manganite of calcium ; but his compound contained five 



