322 
PHARMACEUTICAL MEETING. 
Shaking iviih air causes great variation in the igniting-point of a specimen of 
petroleum. A fresh specimen of the same refined “ Ladoga ” oil was gradually 
warmed in a bottle, the specimen being violently shaken before the test-flame 
was introduced. In this way explosion actually took place at 78° F. This was 
an extreme experiment, but it serves to show the influence which more or less 
shaking or, so to speak, washing out of the vapour from the oil by air, exerts 
on the point of ignition. It is true that when once in a lamp petroleum is not 
likely to be much shaken about, yet there are other circumstances under which 
violent agitation may take place ; it is only fair therefore that in taking the 
point at which a specimen of petroleum evolves inflammable vapour, some 
amount of stirring or agitation should be practised. 
The distmice of the test-flame from the petroleum may cause variation in ob¬ 
serving the igniting-point. The amount of vapour evolved in a given time 
may be sufflcient to form a small quantity of explosive mixture near the surface 
of the petroleum, but not at an inch or two from the surface, hence an operator 
dipping the test-flame down to the surface of the liquid, or even below the sur¬ 
face, to see if the oil will extinguish instead of being ignited by his flame, will 
give a lower igniting-point of the vapour than an operator who only brings his 
test-flame within an inch of the surface of the oil in a basin, or only just within 
the mouth of a bottle or gallipot. In an experiment with the “ Ladoga ” oil 
this cause of error made a difference of 4° in the observed igniting-point. 
The amount of i~)etroleum operated on in comparison with the size of the vessel 
in which the operation is performed will, of course, influence the observations, 
for the reason just stated. An operator making his experiments in a bottle or 
deep beaker or gallipot, and always introducing the test-flame only just within 
the mouth, will sooner meet with the explosive mixture if the vessel is three- 
fourths full, than if that mixture has first to fill the upper part of a vessel onl}^ 
one-fourth occupied by the liquid. 
These, then, are causes, amply sufficient in number and nature, of the varia¬ 
tion in the igniting-point of petroleum, as observed by different experimenters, 
or by the same experimenter at different times. They fully explain the fact 
that I have found a specimen of petroleum to ignite at almost any degree be¬ 
tween 78° F. and 124° F. Before proceeding to suggest a modified method of 
observation which shall give constant results, it may be instructive to give a 
table of the igniting-points of several specimens of refined petroleum recently 
circulating in wholesale and retail commerce,^ the experiment on each specimen 
being taken under three conditions:—first, heating in an oj^en earthenware 
bowl, of the form, etc., already described; second, heating in a two-ounce, 
wide-mouthed, white glass phial, without shaking the petroleum ; and third, as 
the second, except that before introducing the test-flame the stopper was in¬ 
serted in the bottle and the whole well shaken for three or four seconds. It 
will be noticed that differences of igniting-point in any one specimen are ob¬ 
tained varying from ten to thirty degrees. The other causes of variation already 
alluded to were excluded by the experiments being all performed by one ope¬ 
rator of experience, each set of experiments being made under equal conditions, 
and each experiment occupying the same amount of time,—about three minutes. 
The table wiU also serve to show what the ‘ Lancet ’ showed (March 29, 1862) 
in regard to mineral oils sold in London, and what the observations of O’Neill 
showed at Manchester in June 1862 (‘ Chemical News,’ vol. v. p. 312), and of 
Tate at Liverpool, in September 1862 (‘Pharmaceutical Journal,’ vol. iv., new 
series, p. 150), namely, that much of the petroleum supplied to the public 
is dangerous. In addition it shows that, as much of it (in the words of the Act) 
* For the foimer I have to .thank Messrs. Eose, Graham, and Wilson, of Tlueadneedle 
Street. 
