Chemical Science. 617 



8. ON THE SPONTANEOUS INFLAMMATION OF PULVERIZED CHAR- 

 COAL. (Aubert.) 



Spontaneous inflammation of pulverized charcoal occurred in 1802, at 

 the powder-works of Essonne ; in 1824 at those of Bouchet ; in 1825 

 at those of Esqucrdes ; and in 1828 at those of Metz. The latter 

 gave occasion to an investigation, of which the following is an 

 account. 



Pulverized charcoal had to be prepared for the Polytechnic School ; 

 the operation was commenced on the 31st of March, 1828; the char- 

 coal was made from dry bourdine (peach ?), by distillation, 25 per 

 cent, of charcoal being obtained. Twenty-four hours after, the char- 

 coal was weighed, and then triturated for five hours with bronze balls 

 from 7 to 10 millimeters (0.275-0.394 of an inch) in diameter, in 

 leather tuns 1 meter (39.37 inches) in diameter, and 1 . 15 meters 

 (45.27 inches) in height, making 30 revolutions in a minute. Each 

 vessel contained about 10 kil. (221bs.) of charcoal, and balls to the 

 amount of 35 kil. (77 Ibs.) ; the trituration was continued three 

 hours. The triturated charcoal was spread out during a new tritura- 

 tion, and ultimately put into casks. During six years that charcoal 

 with sulphur has been thus triturated, no accident of the kind has 

 occurred, and the temperature of the tuns never rose more than 45 

 or 54 F. above that of the workshops. Nevertheless, on the 3rd of 

 April, 80 kil. (176 Ibs.) of the charcoal, pulverized on the preceding 

 days, and put into a cask, had inflamed spontaneously. 



A new operation produced the same results ; the same quantity, 

 triturated in one day, was divided and put into two barrels ; on the 

 morrow fire appeared in the barrel containing that portion triturated 

 in the morning; the other gradually heated, but did not inflame. 

 Thus pulverized, the charcoal is excessively divided, it assumes an 

 oily appearance, occupies only one-third the space it has whilst in 

 cylinders, and contains six-thousandths of bronze. 



In examining the cause of this action, attention was first paid to 

 the mode of carbonization : one portion of charcoal was distilled at 

 a high temperature in close vessels ; 100 parts of wood yielded 25 

 of black carbon : the other was made in open cast-iron vessels. 

 Forty-eight hours after their manufacture, these charcoals were tri- 

 turated as before for three hours, but as 40 kil. (88 Ibs.) were 

 required for their ignition, whilst only about a third of that could be 

 pulverized at once, each was done at thrice, and the products put, 

 as obtained, into two barrels for the two kinds of charcoal. The 

 barrels were placed side by side ; each contained about 42 gallons, 

 and were covered with cloth. During the trituration the temperature 

 of the tuns above the surrounding space was alike, and was from 

 27 to 43 F. 



Each cask, with its 42 kil. (92J Ibs.) of charcoal, was closed 

 by a wooden cover with two holes, one at the middle, the other at the 



