Ch.\p. XXYIII.] maxcfacture of ferro-maijganese. 
589 
beneficial ; hence it is necessary to add a quantity of alloy sufiicient for 
some manganese to he left in tlie steel after tlie removal of the oxygen. 
Penrose says that the amount of the alloy added varies from 1 to 5% of 
the steel, according to its metallic contents, and according to the amount 
of manganese it is desired to leave in the steel. The amount left in 
ordinary mild steel, such as is used for rails, varies from less than 
0-5% to over 2%, but is not as a rule much over 0-5%. As the man- 
ganese alloy always contains silicon and phosphorus and other im- 
purities, the less of it that has to be added the better ; also the less 
that has to be added the milder can the resulting steel be made. Hence 
high-grade ferro-manganese is usually preferred to the lower grade 
spiegeleisen. 
In paper on the covering of the demand for manganese-ores 1, 
W. Venator takes an average consumption in the iron and steel industry 
of 1 '3°Iq of manganese as necessary per ton of steel produced. The 
50,000,000 tons of steel produced by the world in 1906, would thus 
account for a consumption of 650,000 tons of manganese, or 1,300,000 
tons of 50°/q manganese-ore, out of the 1,445,000 tons of ore produced 
in that year. 
As regards the impurities permissible in the alloy used 0. Simmers- 
D, , , .,. bach gives it as a rule that spiegeleisen with 
Phosphorous and sihcou c . 
in spiegeleisen and ferro- 20% Mn should not contain more than 0-1% of 
niangane-e. phosphorus, and for every IOOq Mn above this 
the phosphorus contents should not increase by more than 0 02%, 
so that ferro-manganese with 80% Mn should not contain more than 
0-1 -|-(6 X 0-02)=0-22% P. The standard for silicon is spiegeleisen 
containing 20% Mn and 1% Si with a pernussible increase of 0-1% Si 
for every 10% increase in the manganese ; hence 80% ferro-manganese 
should not contain more than l-0-|-(6 xO-l)=:rl-6% siUcon. From 
the above we see that ore of the composition given on page 586 
should not, if it is to give 80°/^ ferro, contain more than 0-1 16% or, say, 
0-12% of phosjjhorus. The average figure for phosphorus given there is 
0-10. This is possibly a trifle higher than that of the ore exported ; 0-08 to 
0-09 would probably be a more accurate figure. The ores of the Central 
Provinces are therefore within the phosphorus limits necessary for high 
grade ferro. Of ores exported from other parts of India, those of Mysore 
and Sandur are well within the Hm.its. But those of Jhabua (0-16-0-27°o P) 
and the Panch Mahals (015-0"25% P) are over the Kmit, and those of 
1 ' Die Deckung des Bedarfs an Manganerzen ', StaM. u- Eisen, XXVI, p. 66, (1906). 
