136 PRELIMINARY REPORT ON COAL-TESTING PLANT, [bull. 261. 
This machine is adapted only to those binders which do not become ! 
plastic before reaching the pug- mill, and in the experimental work 
the smallest quantity that could be made and at the same time give a 
satisfactory test to the coal and binder was 1 ton. 
AMERICAN MACHINE. 
In operating the American plant the coal is received from the Rob- 
ins conveyor at the level of the second floor in a bin of 3 tons capacity. 
From this it is spouted to a 500-pound bin on a Fairbanks platform) 
scale, from which it passes into the boot of an elevator that hoists itl 
up and drops it into a 15^ cubic foot measuring box. The coal is then! 
dumped into a Buffalo mixer fitted with steam jackets for warming the] 
coal and the binder. The binder is melted in a small steam jacketedl 
tank entirely distinct from the main part of the machine, from which] 
it is dipped by hand in the desired proportion and poured into thel 
mixer. After a thorough mixing the mass is dropped into the feed slides] 
of the press. This tangential press consists of two pairs of narrow-1 
faced rolls, in the tores of which are ovoid cups for receiving the mix-J 
ture to be pressed. As the rolls revolve the excess material is squeezed! 
out, the resulting pressure being dependent upon the viscosity of the 
mixture that is being compressed. The eggettes are delivered from 
the press on a short rubber belt, and they weigh on an average aboil 
0.3 of a pound each. 
The capacit}' of the press is fully 5 tons of eggettes per hour, bul 
the output of the mixing device was much too small for operating the 
press at its full capacity. As arranged, this machine was adapted forr 
the use of soft binders only, and it was necessary to grind the coal att 
the washery. For experimental work, however, it had one advantage 
over the larger English press, inasmuch as it permitted the testing oil 
mixtures in lots as small as 15 pounds. In making these small tests a 
35-gallon camp kettle was employed for heating the mixture. It wasj 
also possible to test on the American machine the mixture used in the 
English machine by crushing up some of the hot briquettes as soon as 
they were received from the molds and transferring the material ai 
once to the feed box of the American machine. 
BINDERS. 
The materials that have been tried as binders in the laboratory 
experiments and on the two briquetting machines include the follow 
ing: Pitch of various grades; creosote; asphalt, hard and soft, crud 
and refined; asphaltic pitch; petroleum, both of paraffin and asphal 
bases; molasses; lime, and clay. 
PITCH. 
Pitch is the residue left from the distillation of tar, which is pre • 
duced (1) from by-product coke ovens; (2) from illuminating-gas plant; j 
(3) from producer-gas plants; (1) from pintsch gas tar; (5) from wat< if 
