Compositors in addition to chronic lead poisoning may suffer, it is alleged, from chronic antimony poisoning, showing itself in diminution in the number of white blood corpuscles and marked eosinophilia. These changes in the blood could be brought about experimentally in rabbits. Antimony was found by the Marsh test in the stools of those affected.
IRON
Pig iron is obtained by smelting iron ores in blast furnaces ([fig. 29]), through the upper opening of which charges of ore, limestone or similar material to act as a flux, and coke are fed in succession. The furnaces are worked continuously, using a blast of heated air; carbon monoxide is produced and effects the reduction of the ore to molten iron. The latter accumulates in the hearth and is covered with molten slag; this flows constantly away through an opening and is collected in slag bogies for removal, or is sometimes cooled in water.
The crude iron is tapped from time to time, and is led in a fluid condition into moulds called ‘pigs,’ in which it solidifies. Cast iron is occasionally used direct from the blast furnace for the purpose of making rough castings, but generally it is further refined before being used in a foundry by remelting with cast iron scrap in a cupola furnace.
Fig. 29.
a Hearth; b Bosh; c Shaft; d Gas uptake; e Down-comer; f Tuyères with water cooling arrangement; g Blast pipes; h Tapping hole; k Supporting columns; l Furnace bottom; m Charging hopper; n Bell with raising and lowering arrangement.
Wrought iron is made by treating pig iron in refinery and puddling furnaces; in these much of the carbon is removed as carbon monoxide, and from the puddling furnace the iron is obtained as a pasty mass which can be worked into bars, rods, or plates.