500 Journal of Agricultural Research voi. xxviii, no. 6 
indicated by the machine at the point of failure of the briquette was taken as its 
breaking strength. The average of three or four such determinations was taken 
in each instance. The dry weights of the briquettes varied considerably with 
different materials; so for comparative purposes, the average load was divided 
by the weight of the briquette, giving the load per gram of material. By divid¬ 
ing the load per gram of material by the amount of colloid in one gram of the 
material, the load per gram of colloid was determined. 
For the purpose of forming the briquettes a hydraulic pump (fig. 1) was used. 
A brass cylinder (fig. 2) was drilled with a 31/32-inch drill, bored to 63/64 inch 
and lapped out with a lead lap. This made the diameter of the opening 25 mm. 
A steel piston was turned out so that it slipped easily into this opening and was 
made water tight at its lower end with a leather washer. A small auxiliary cap 
was made to fit the opening at the top of the cylinder and a larger cap made to 
screw on over this. The purpose of the small cap was to protect the surface of 
the briquette when the outer cap was removed. The cylinder was attached to 
the pump, as shown in figure 1. 
Fig. 1.—Hydraulic pump used in molding briquettes 
