318 
ON THE CAUSE OF EXPLOSIONS IN LAMPS* 
BY JOHN ATTFIELD, PH.D., F.C.S. 
Director of the Laboratory of the Pharmaceutical Society of 
Great Britain. 
URING the last two months I have been investigating 
the inflammable properties of mineral oils; at first, 
for the scientific interest the subject presented, then by de- 
sire of the Committee of the Petroleum Association of the 
City of London, and recently in elucidating the cause ofan 
explosion of a lamp, at a house of a gentleman in the coun- 
try, Thomas Smith, Esq., the Croft, Sudbury. Iam now, 
consequently, in a position to state the immediate cause of 
explosions in lamps, to show how it is, that oils having dan- 
gerous properties occur in trade, and to point to more than 
one means whereby the use of mineral oils for illuminating 
purposes may become as safe as that of the old, less valu- 
able, vegetable oils. 
The oil in a lamp passes up a wick by capillary attrac- 
tion, comes in contact with the brasswork of the lamp in 
the long slit or channel which holds the wick, and finally 
burns at the top of the wick by help of a strong current of 
air. The flame heats the brasswork in its vicinity, the heat 
is conducted downward through the metal to the body of 
the lamp, and thence to the oil, which after two or three 
hours becomes considerably warmer than when the lamp 
was first lit. Now mineral oils, when sufficiently heated, 
emit vapour which form, with air, a dangerously explosive 
mixture. The point to which any specimen of mineral oil 
must be heated before it yields this mixture can be ascer- 
tained readily and with perfect safety by the method pro- 
posed inmy last paper “Onthe Igniting-point of Petroleum,” 
namely, by half filling an ordinary chemist’s test-tube. 6 in. 
long, and 14 in. broad, warming, and well stirring with a 
naked thermometer until a small flame, frequently intro- 
duced into the upper part of the tube, occasions an explo- 
sive flash; the temperature indicated by the thermometer 
at this moment is the point of danger. Tested in this way 
the oil from Sudbury afforded inflammable vapour at 83 
degrees. But, curiously enough, the temperature of the 
bulk of the oil in the lamp that exploded never reached 
* From the Pharmaceutical Journal, January, 1867. 
