316 The N.Z. Journal of Science and Technology. [Sept. 
contained lime may suffice. The mixture is made hydraulic (i.e., the silica 
is made soluble) by steaming, and is then briquetted at 1,500 lb. per square 
inch, and steamed for ten hours at 150 lb. pressure. A good but costly 
brick is made, which is quite suitable for blast-furnace use. 
In the Weiss process limestone is added to the ore together with 5 per 
cent, of powdered h}ffirated lime. Briquettes are made at 2 tons pressure, 
and are hardened by the action of cold C0 2 at a pressure of 300 lb., and 
afterwards by being exposed for about four hours to C0 2 mixed with waste 
gases from the furnace in which the C0 2 is made by heating limestone. 
Another process adds 6 per cent, of a mixture of sand and slaked lime. 
The briquettes are made hydraulic by superheated steam. 
These five processes all depend on the formation of the gelatinous 
ferric * hydroxide (Fe 2 G 6 H 6 ). The last four are costly, both for initial 
outlay and working-expenses, and have the disadvantage of adding a 
medium containing no iron to the briquette. The amount of handling 
required is also a drawback. 
The Trainer, Pioneer, and Pollacsek processes use sulphite liquor (cell- 
pitch from the preparation of paper-pulp) as a binding-medium, but the 
financial success is doubtful, as the pitch is expensive. 
The use of clay, slaked lime, and of molasses for a binding-medium 
has been extensively tried, but each has been abandoned for commercial 
reasons, although technical success has been achieved. 
In other cases experiments have been tried with various binding- 
mediums, such as silicate of soda, silicate of potash, asbestos, basic slag, 
naphthalin, paraffin, peat, salt, and other organic and inorganic substances, 
but “ as there is no reason to believe these will ever be tried again, the 
author does not consider it necessary to go into details about them."* 
Fusion or Vitrification without Pressure .—These are not true briquetting 
processes, but the dust is agglomerated, nodulized. sintered, or clinkered 
by heat. Rotary kilns are used for treating ores and flue-dust in a similar 
manner to the burning of cement clinker. Powdered fuel is generally used 
for heating, but gas and oil have also been used. The dust in its passage 
through the rotating kiln (often 10 ft. in diameter by 125 ft. in length) is 
gradually dried, desulphurized, and finally nodulized to lumps varying 
from a pin-head to ljin. diameter. The product is generally magnetic 
and therefore refractory, and it is difficult to keep the walls clear of the 
clinkered ore ; but the process- is cheap (under 4s. a ton in America), and 
the nodules suitable for the blast furnace. 
In the Heberlein pot process the ore is agglomerated by heating in a 
pot resembling a Bessemer converter. A fire is built on the grate, and 
an up-draught of air at a pressure of 15 in. of water carries combustion 
through the mass. When burning is complete the pot is tilted and the 
mass broken by dumping on to a screen, which sifts out any fines remaining. 
A hard dense sinter is made. 
The G-reenawalt process uses a tilting pan, 8 ft. diameter by 12 ft. deep, 
on the grate of which a mixture of ore and up to 11 per cent, of coal (or 
flue-dust) is ignited by an oil flame, and combustion is then completed by 
a down-draught. 
The Dwight-Lloyd apparatus comprises a series of pans carried on an 
endless conveyor. On the grates of these pans ore and fuel is fed from a 
chute and ignited by oil or gas. Combustion is carried downwards by an 
* Mr. de Schwarz has probably underestimated the ignorance of inventors and 
the gullibility of investors.—S. H. J. 
