Spontaneous combustion of coal

Spontaneous combustion of coal

NOTES FROM THE SPONTANEOUS U. S. BUREAU COMBUSTION OF MINESt2 OF COAL. By J. D. Davis. EXPERIMENTS in the spontaneous heating of coal in presenc...

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NOTES

FROM THE

SPONTANEOUS

U. S. BUREAU COMBUSTION

OF MINESt2 OF

COAL.

By J. D. Davis. EXPERIMENTS in the spontaneous heating of coal in presence of an excess of oxygen were conducted under such conditions that all of the heat generated by oxidation of the coal was employed This was done in order that the rates in raising its temperature. of heating would he a measure .of the tendency for spontaneous heating of the coal. All the coals treated were ground to IOO mesh. It was found that (I) the tendency to heat was greater for coals high in oxygen than for coals low in oxygen, although not directly proportional to the oxygen content ; (2) the heating tendency of coals of similar rank was approximately the same ; (3) the rate of generating heat in spontaneous combustion is directly proportional to the amount of oxygen used. Further details are given in a paper presented before the meeting of the American Chemical Society at Ithaca, New York, September 8, 1924.

FILTER

SAND

FOR

MUNICIPAL

By M. W.

WATER

SUPPLY.

Weigel.

THE use of sand for the filtration of municipal water supplies is of comparatively recent use in this country, although at the present time, most cities of any size that draw their water supply from surface sources use sand filters in their purification system. Kot only are sand filters employed to remove sediment and suspended matter, but they also take out most of the bacteria in the water. The writer recently completed a study of filter sand, its requirements, specifications and methods of mining and preparation. The general requirements for filter sand are more .exacting than for any of the different kinds of sands, except the chemical specifications for glass sand. Filter sand must be uniform in size and within certain limiting sizes. In addition, it must be * Communicated

by the

Director.