hO Dr. Forchhammrr on pun Salts of Manganese, [J4.N. 



mum of effect takes place, or whether indeed there be any term 

 of this kind. It will be next desirable to learn what is the lowest 

 temperature at which the volatile oil and the water are respect- 

 ively generated, and to examine at different temperatures, and at 

 different periods of time, the proportion which these substances 

 bear to each other. It will likewise become a very curious 

 subject of investigation to learn with more accuracy the nature 

 and properties of the inflammable vapour, whether it consist 

 merely of the volatile oil in a vaporized state, or of this mixed 

 with some permanent gas ; if so, whether the gas resemble any 

 species of carburetted hydrogen with which we were previously 

 acquainted. Lastly, we must investigate the nature of the vola- 

 tile oil, when obtained in a separate state by distillation, and 

 also that of the acid generated in the latter part of the opera- 

 tion, whether it be actually the acetic acid, or in what respect 

 it differs from this acid as obtained by the ordinary processes. 



Article XII. 



On the Preparation of pure Salts of Ma?iganese, and on the 

 Composition of its Oxides. By G. Forchhammer, Ph. D. 



The principal ore of manganese wrought for the preparation 

 of chlorine is the common grey ore of this metal, or the peroxide. 

 I have tried several of the ores which occur in Germany in veins 

 and beds in a porphyry belonging to the first secondary 

 sandstone, and found them all containing some copper, in 

 very small quantity, excepting of course the complete crystals 

 of it which are generally free from this admixture. It appears 

 that the Devonshire ore is found in the same geognostic position 

 as those above-mentioned ; and 1 found this likewise containing 

 some traces of copper, which, though the combination does not 

 bear the character of a chemical compound, is a striking instance 

 of the similarity in the formation of the same mineral in far dis- 

 tant countries. Besides copper, iron always is present, and 

 a small quantity of barytes, and even of lead, occur very 

 often. Iron, however, is an admixture, the separation of which 

 has generally been the most attended to ; and many chemists 

 have attempted to remove it by simple processes. There is no 

 doubt that the benzoate and succinate of any alkali will throw 

 down all the deutoxide of iron ; but if there is protoxide, it may 

 escape to a certain degree, and then these salts are so expensive 

 that, for preparing a quantity of the pure oxide of manganese, it 

 would be desirable to find another process. The method I 

 made use of is the following : I prepared in the common way 

 sulphate of manganese by heating equal parts of peroxide of 

 nxanganese with sulphuric acid, only taking care to keep it in 

 the lire until vapour of sulphuric acid ceased to appear; 



