Chap. XXVIII.] manufacture of ferro-manganese. 
585 
barytes as there is silica present in the ore and fuel. An actual example 
of the charge used at Terre Noire is the following : — 
Huelva ores, pyrolusite, 9-6 cwts., with Fe= 2-91%, Mn= 52-50% 
Almoria do. do. 4-0 Fe= 15%^ Mn= .50 % 
Tafna. do. hematite, 0-4 Fe= 55% 
Total : — 14 cvvts. ore, containing average of 4°i', Fe, and o0-28°o Mn. 
P'or this are required : — 
Limestone . . . . . . . . . . 4-4 cwts. 
Barytes . . . . . . . . . . 1-2 cwts. 
Or more conveniently we can say that 1 ton of manganese-ore, aver- 
aging 50% Mn and 4% Fe, requires 6-3 cwts. limestone, and 1-7 cwts. 
barytes. The product was ferro-nianganese containing — 
Manganese.. .. .. .. .. 83 90 
Iron . . . . . . . . . . 8-83 
Carbon & silicon .. .. .. .. 7 26 
99-99 
and the loss of manganese was 25%. 
Judging from the amount of limestone used the average silica percent- 
age of the ores used mtist have been about 8%, assuming none to have 
been derived from the fuel. Consumption of coke was 54 cwts. per ton 
of ferro made. 
According to T. Turner 1, in smelting spiegeleisen, the charges are 
calculated for a reduction of 75% of the manganese into the alloy, and 
with ferro-manganese for a reduction of 80% of the manganese. Accord- 
ing to Simmersbach good ferro-manganese slags contain 7 to 10% of 
manganese, according to the composition of the ferro-manganese, whilst 
up to 18 to 20% is not uncommonly found in the slag v/hen easily fusible 
ores are smelted. Besides the loss of manganese that takes place by 
passage into the slag, there is also a considerable loss through volatiliza- 
tion in the blast-furnace ; this may range up to 17% and over of the ori- 
ginal manganese contents. When casting it is necessary to shut off the 
blast, as otherwise the composition of the metal might be seriously altered 
both by volatilization and oxidation. Owing to the corrosive action of 
the manganiferous fumes from the blast-furnace on stonework, it is 
advisable to pass the furnace gases through a washer or dust-catcher 
before letting them into the fire-brick stoves. If the ore is highly oxidized, 
containing a high percentage of Mn02> the gases derived from the furnace 
1 • Metallurgy of Iron p. 150, (1895). 
Ill M 
