BASIC CIXDER AS MANURE. 
Basic cinder, known also as basic skg, Thomas' slag, Thomas' 
phosphate powder, and Thomas' powder, is a product of* a process 
for converting phosphoric pig-iron into steel for which a patent 
was taken out by Messrs. Thomas & P. C. Gilchrist in the year 
1879. About 83 per cent, of the known deposits of iron ore in 
Great Britain are phosphoric to the extent of containing one 
part or more of phosphorus per thousand of iron ; probably this 
ratio holds good with the known iron ores of the world. In smelt- 
ing this ore to make pig-iron, practically the whole of the phos- 
phorus of the ore goes into the pig-iron. Such phosphoric pig 
is not suitable for making steel by the ordinary Bessemer, or by 
Siemens' process, as the phosphorus remains in the steel, and 
renders it "cold short." It follows, that only about 15 per 
cent, of iron ores, chiefly haematite, which are nearly free 
from phosphorus, can be used in steel-making by these pro- 
cesses. 
Pig-iron made from the Cleveland, Staffordshire, Scotland, 
and other similar iron ores, contains phosphorus varying usually 
from about O S up to 3 per cen\ Pig-iron of this class can now, 
by the Thomas-Gilchrist process, be readily converted into first- 
class steel and ingot-iron. 
The process most commonly used is a modification of the 
Bessemer process, though it may also be adapted to the Siemens' 
process, of steel-making. The " converter " into which the 
molten cast-iron is run is lined with magnesian limestone instead 
of with the usual siliceous ganister. Lime to the extent of 
about 1 5 or 20 per cent, of the weight of the cast-iron is thrown 
into the converter at the beginning of the " blow." 
The " blow " — a powerful blast of air forced through the 
molten metal — is conducted as in the ordinary Bessemer process, 
but is continued a little longer than in the ordinary plan. 
The oxygen of the air unites with the impurities of the pig-iron, 
with the phosphorus to form phosphoric acid, which in its turn 
unites with the lime to form phosphate of lime. Some of the 
iron is also oxidised to form ferrous and ferric oxides. When 
the "blow " is finished — in about fifteen minutes — most of the 
oxidised substances are found floating on the surface of the steel 
as slag, or cinder, which is then removed by tipping the con- 
verter. This cinder forms a dark-coloured, vesicular substance, 
containing an admixture of fragments of steel and separate 
crystals of phosphate of lime. 
VOL. I. T. S.— 1 K 
