378 
PHARMACEUTICAL MEETING. 
the paper, and that was in recommending the omission of distillation. Ilis ex¬ 
perience was, that preparations of this character were greatly improved by dis¬ 
tillation, especially where they contained essential oils, such as oil of lemons. 
This essential oil, as met with in commerce, although sometimes distilled, was 
generally an expressed oil, and in either case it resembled oil of turpentine in 
the readiness with which it became resinified. When submitted to distillation 
there was a considerable residue of a bitter substance left, which, if added to 
sal-volatile, would not improve its quality. 
Mr. Umney agreed with what had just been stated. He had found that 
essence of lemon, even after it had been once distilled, underwent a similar 
change to that which occurred in oil of turpentine. 
Dr. Attfield thought that distillation was not only desirable in the case of 
sal-volatile but also in that of essence of lemon. 
The Chairman said spirit of sal-volatile was extensively used, and was a re¬ 
medy the qualities of which the public thought themselves capable of appre¬ 
ciating, and he thought it important in such a case that no means should be 
omitted by which it could be made to suit the public taste. 
Mr. Mackay’s experience was strongly in favour of carrying out the process 
as ordered in the Pharmacopoeia; in fact, he might say, that not an ounce would 
ever leave his establishment that was not distilled. He had had much experience 
in the different qualities of oil of lemons, and thought the best oil ought to be 
used for making sal-volatile. He thought the nose was the best criterion of 
quality. 
ON THE CAUSE OE EXPLOSIONS IN LAMPS. 
BY JOHN ATTFIELD, PH.D., F.C.S., 
niKECTOR or THE EABORATOEY OF TUE FHAEMACEUTICAE SOCIETY OF Q-liEAT BEITAIX. 
During the last two months I have been investigating the inflammable pro¬ 
perties of mineral oils ; at first, for the scientific interest the subject presented, 
then by desire of the Committee of the Petroleum Association of the City of 
London, and recently in elucidating the cause of an explosion of a lamp, at the 
house of a gentleman in the country, Thomas Smith, Esq., the Croft, Sudbury. 
I am now, consequently, in a position to state the immediate cause of explosions 
in lamps, to show hovv it is that oils having dangerous 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 valuable, 
vegetable oils. 
The oil in a lamp passes up a wick by capillary attraction, 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 down¬ 
ward 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 sufliciently heated, emit vapours 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 ascertained 
readily and with perfect safety by the method proposed in my last paper “ On 
the Igniting-point of Petroleum,” namely, by half-filling an ordinary chemist’s 
test-tube, G in. long and 1-| in. broad, warming, and well stirring with a naked 
thermometer until a small flame, frequently introduced into the upper part of 
the tube, occasions an explosive flash ; the temperature indicated by the ther¬ 
mometer at this moment is the point of danger. Tested in this way, the oil 
