Chap. XXVIII.] use as an oxidizer. 597 
in the same way as in the manufacture of mild steel, whilst the manganese 
left in the klieri may exert some effect in keeping the carbon in the com- 
bined condition. It is to be noted, however, that although the hheri 
is much superior in hardness to the soft iron, so that the faces of the 
hammers and anvils assume a smooth shining mirror-like appearance 
under the influence of constant impact, yet one of these shining surfaces 
was easily dented by the corner of my geological hammer. Of the man- 
ganese in the iron-ore from which the soft iron is manufactured, it will 
be seen that practically all has left the iron and has hence passed into 
the slag, except for a small portion found in the shot. T did not see the 
use to which the shot are put, but I was told that they are made into 
plough-shares, the iron thus made being harder than the soft iron, but 
more liable to break. If the composition of the finished metal be like 
that of shown by the analysis, the ploughshare metal must be interme- 
diate between cast iron and steel. An account of the manufacture of 
Men is given by P. N. Bosei. 
Use as an Oxidizer. 
We can now turn to the use of manganese-ore as an oxidizer. For 
this purpose the value of the ore does not 
Use of manganese as , -, , r 
an oxidizer. depend on the amount of manganese it 
contains, but on the amount of available- 
oxygen, i.e., oxygen that can be obtained from it by the action of acids. 
This available oxygen is usually stated in terms of manganese peroxide 
(MnOg). The mineral containing the largest amount of Mri02 is of 
course pyrolusite, which when pure consists of 100% of Mn02.2 
Psilomelane, also, often contains a considerable quantity of Mn02. 
Psilomelane is, as noted in Chapter IV, a manganate corresponding to 
the general formula ^^nO^. If the R consisted entirely of 
manganese, giving a formula for the mineral of Mn2Mn05, then the 
amoimt of MnOo present in the theoretically pure mineral would be 
77-33%. Going to the other extreme, if the R consisted entirely 
of hydrogen, a condition not approached even nearly in Nature, 
then the formula of the compound would be H^MnOg, and the 
amount of Mn02 in the theoretically pure compound would be only 
62*57%^. But it will be seen that after deducting 2H20^ the radicle 
Mn03 is left ; in this case, therefore, it would be misleading to state 
1 Rec. G. 8. I., XXI, pp. 87, 88. (1888). 
2 Polianite also has this formula, MnOg, but it is too rare to be considered conimer. 
cially. 
