42 OPERATIONS OF FUEL-TESTING PLANT IN 1905. 
TESTS OF BINDING MATERIALS. 
There is need for much additional investigation on a larger scale before definite results 
can be stated concerning the several possible binding materials for briquette manufacture; 
but the examinations made by Doctor Mills developed certain results which are at least 
suggestive. 
The use of inorganic binding materials such as those mentioned above is not likely to 
prove practicable under any ordinary conditions, except that in the case of noncoking 
coals, when coking coals can not be obtained to mix with them, a small percentage of 
certain of these materials (such as magnesium oxide or carbonate, plaster of Paris, etc.), 
if added to other binding materials, may cause the briquettes to hold together better in 
the fire and hence undergo more complete combustion. It was not expected that all of 
these substances could be successfully used as binding materials in the manufacture of 
briquettes; nevertheless it was believed that an examination of each substance as to its 
adaptability for this purpose might throw some light on the general problem under con-: 
sideration. 
Of the more specific results in the testing of different binding materials, the following 
tentative statements are made, pending further investigations: 
The use of clay, lime, and cements as binding materials was found entirely unsatisfac- 
tory, for the reason that they add largely to the ash constituent of the briquette. The 
briquettes made with these materials as bond went to pieces on exposure to water and 
weather and their waterproofing by soaking in oils, etc., was found difficult and expensive. 
Water glass (or soda silicate) was also found to be unsuitable for use in this connection. 
From 4 to 6 per cent of magnesium oxide used as a binder was found to hold the bri- 
quettes together satisfactorily in dry weather and in the lire, but they disintegrated on 
exposure to rainy weather or when immersed in water. 
In the tests with plaster of Paris, from 2 to 12 percent of this material being used as a 
binder, the briquettes made were hard but brittle, and quickly disintegrated on exposure 
to moisture. Three per cent of magnesia mixed with 6 to 8 per cent of water-gas tar pitch 
seemed to make a stronger briquette than the same percentage of pitch used alone; but 
the improvement in the quality of the briquette is not considered sufficient to cover the 
additional cost of the magnesia and the additional percentage of ash which it brings into 
the briquette. Furthermore, this addition of sulphur to the coal is undesirable. 
None of the sugar-factory residues, namely, beet pulp, lime cake, beet-sugar molasses, 
and cane-sugar molasses, were considered satisfactory as binding materials, for the reason 
that the briquettes made with them disintegrate on exposure to the weather, and no inex- 
pensive waterproofing has as yet proved satisfactory on a commercial scale. 
Nor were any of the wood products, including rosin, pitch, pine-wood tar, hard-wood 
tar, Douglas-fir tar, wood pulp, and sulphite liquor from paper mills, when used alone 
regarded as satisfactory, though some of these materials used in combination with other 
binders gave results of some promise, and deserve further investigation. 
The tests made using from 0.5 to 3 per cent of starch as a binding material with different 
coals gave briquettes which were strong, w r ere smokeless in burning, and held together in 
the fire until completely consumed; but these briquettes went to pieces when wet or exposed 
to the weather for a considerable period of time. Experiments as to the possibility of 
cheaply waterproofing the briquettes bound with starch, so as to make them hold together 
when exposed to water, were sufficiently successful to warrant further investigation in 
this direction. Starch is obtainable in large quantities and can be easily produced in 
almost any part of the country. In its crude form it can probably be obtained at a price 
less than $20 per ton. At this price, the use of 1 per cent of starch as a binder would add 
only 20 cents per ton to the cost of the briquettes. 
The scarcity and high price of slaughterhouse refuse would prohibit its use as a binding 
material for briquettes, even if the tests with it were otherwise satisfactory, which was not 
the case. 
