Chap. XXVIII.] use .\s ax oxidizer. 
599 
purposes the best ore is pATolusite. but that psilomelane is often good 
enough ; whilst the other ordinary ores of manganese are of little or no use. 
The chief chemical use of manganese-ore is for the manufacture of 
clUorine, and before the use of manganese in the metallurgy of iron and 
steel, this accounted for by far the larger proportion of the consumption 
of manganese-ore. Of recent vears. however, the demand for manganese- 
ores for the manufacture of chlorine has decreased o\\-ing to the manu- 
facture of chlorine electrolytically. For chlorine manufacture not only 
must the ore be as high in Mn02 as possible, but the impurities making 
up the remainder of the ore should be such as are insoluble in hydro- 
chloric acid. Thus ore containing 75"^o manganese peroxide would be of 
more value if the remaining "25^0 were quartz, than if it were iron oxide or 
carbonates. Owing to the fact that soft ores are more qmckly attacked 
by acid than hard ones, pvrolusite is preferable to psilomelane, even when 
the two contain the same percentage of MnOo. There are many deposits 
in India where a fair quantity of p^Tolusite, ranging over 70% of MnO.?, 
can be obtained ; and at times Indian pyrolusitic ores have been sold for 
chemical purposes. Thus some of the Kodur pyrolusite is said to have 
been bagged and sold for this piupose. as also has some of the Mysore ores. 
The analysis of a picked specimen of Kodur pyrolusite given on page 82, 
shows 92-31% MnOo : whilst bulk samples of pyrolusitic ores from 
Bankuravalsa and Sandanandaptiram in rhe same district show 
71*64 and 72'03Oo Mn02 re.<!pectively (see pages 1105 and 1076). And 
if it were specially required I believe that at several localities a product 
of over 80°o of MnOo could be sorted. It must be remembered that ore 
sold for its Mn02 contents fetches a much higher price than if sold for 
its manganese contents. In the following table the figures given in the 
first and second coliminr are taken from the Engineering and Mining 
Journal for August 3, 1907, page 236, and refer to crude powdered ore. 
In the third column I have converted the price in cents per pound into 
sterhng per ton : — 
Table 91. 
Prices of manganese-ores nold for peroxide. 
Percentage of MnOo. 
Cents per pound. 
Sterling per 
ton. 
£ ^- d £ 
s. 
d. 
TO-75 
4-U 
5 16 S to 7 
0 
0 
75-85 
U-2' 
7 0 0 to 9 
6 
8 
85-90 
lJ-5 
8 3 4 to 23 
6 
8 
90-95 
1 t 
worth £30 6 
8 
