746 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
[March 22, 1873. 
ditions, animal and vegetable oils possess a dangerous pro¬ 
perty from which mineral oils are free. In a series of 
letters to The Times , Professor Attfield recently discussed 
the question of the origin, extension, and prevention of 
fires, and the relation of mineral and vegetable oils and 
other materials to fire. These letters have now been 
issued in a pamphlet form, together with an Appendix, 
in which the Professor gives the results of some experi¬ 
ments made by him, and from which we have taken the 
following. 
Various animal and vegetable oils differ considerably in 
the rate with which they cause the generation of heat 
when exposed freely to the air upon the surface of wool, 
cloth, paper, cotton, jute, saw-dust, lamp-black, ivory- 
black, ground charcoal, or any similar highly porous sub¬ 
stance ; but all are more or less liable to this result of the 
chemical action of air when they are exposed in very thin 
films, or in any other minute state of division. The so- 
called “drying” oils are peculiarly susceptible to such 
atmospheric influences. Common paint exposed on wood¬ 
work becomes “dry” and glossy because the oil of which 
it is largely composed is converted by the action of the 
air into a kind of resin, and during the whole of this 
action heat is evolved. Thus the true chemical nature of 
the effect termed the “ drying” of oils is one in which oil 
is resinified and heat concurrently produced. It is not an. 
operation of drying, in the sense in which a cloth wetted 
with water is said to dry. In the latter case the wetness 
or moisture passes off into the air in the form of vapour 
of water, whereas in the drying of oil no such vapour 
escapes. Nor does oil “ dry,” as varnish dries. Varnish 
is a solution of hard resins in spirit ; in drying, the spirit 
evaporates and leaves the resin. But the oil on any sur¬ 
face exposed to air “dries” to a solid resin by absorption 
of the oxygen of the air. A piece of oiled paper, unlike 
water-wetted or varnished paper, positively increases in 
weight while drying. The true nature of this drying pro¬ 
cess is, therefore, as already indicated, one of oxidation or 
resinification, and simultaneous evolution of heat. The 
emission of heat is not noticed because one painted surface 
affords but little, and because what is produced is at once 
conducted away by currents of air. But when allowed to 
accumulate its presence is most obvious : thus a heap of 
oiled rags soon becomes so hot in the central part that the 
temperature cannot be borne by the hand. As a result 
of direct experiment, I find that paper, cotton, or wool, 
slightly impregnated with different kinds of oil and ex¬ 
posed to air under similar conditions, rises in> temperature 
from 25 to 200 degrees, according to the variety of oil, 
the amount of surface in contact with the air, and the 
duration of exposure. 
Number of 
experiment. 
1 ... 
Temperature at 
commencement 
of experiment. 
... 65°F .. 
Temperature on 
completion of 
experiment. 
, 125°F ... 
Total rise of tem¬ 
perature during 
experiment. 
... 60°F 
2 ... 
... 80 
. 275 
... 195 
3 ... 
... 75 
. 100 
... 25 
4 ... 
... 70 
. 220 
... 150 
5 ... 
... 70 
. 160 
... 90 
6 ... 
... 70 
. 223 
... 153 
It will be understood that in these experiments th© 
escape of heat was purposely prevented. They illustrate 
the statement that during the drying of certain oils heat is 
produced, and will serve to show the extreme importance 
of observing all precautions against the accumulation in 
factories, stores, and warehouses of heaps of oiled rags, 
papers, or other porous materials. In some of my experi¬ 
ments the oiled paper or wool was warmed to about the 
temperature of boiling water before being subjected to the 
influence of air in a closed vessel; in these cases the rise 
in temperature w r as more rapid, and in two instances in¬ 
creased till the mass charred and ignited. Moreover, I 
found that when very large quantities of oiled fabrics were 
exposed in a chamber, the temperature of the air in which 
was made to imitate that obtaining on a hot summer’s 
day, a considerable quantity of vapour, irritating to the 
eyes and readily inflammable, was produced. Such vapours 
would greatly facilitate the spread of flame once started. 
The drying of vegetable or animal oil on any surface is, 
in short, a true process of combustion,—spontaneous com¬ 
bustion,—differing from ordinary combustion of coal in 
fire-grates, or gas or oil in lamps, not in kind, but only in 
degree. To say that coal, wood, fat, etc., bum, is another 
way of stating that they absorb oxygen from the air with 
such avidity as to produce heat and light. So oiled sur¬ 
faces absorb oxygen from the air and produce heat, and if 
the heat were not carried away as fast as generated, would 
become warm, then hot, and next burst into flame. There 
can be no doubt that many fires in oil-shops and ware¬ 
houses where oil is stored or used are caused in this way, 
by the intensified spontaneous combustion of the oil ex¬ 
posed on cotton-waste, sawdust, textile fabrics, etc. I 
was recently consulted in a case where numbers of oiled 
sheets were crowded in a comparatively small room in 
which another operation involving the use of a stove was 
also being conducted. Here were all the conditions for 
spontaneous inflammation. A hot day occurring, or the 
stove being unusually warm, or an ordinary temperature 
with a larger number of sheets than usual, or hung un¬ 
usually near together ; either circumstance, or perhaps a» 
unusual combination of them, would be sufficient to con¬ 
vert the drying or oxidising action, or modified spon¬ 
taneous combustion, into one of spontaneous ignition, or 
ordinary combustion. In another case in which my 
advice was sought in order that steps might be taken 
to prevent recurrence of fire, a similar room was used 
for the desiccation of oiled fabrics. It appears also 
that a sheet-iron flue passed through one corner, carrying 
the smoke and other products of combustion of a furnace 
employed in an adjoining apartment. This flue had often 
been noticed to be red-hot. The men were sure that on 
the day of the fire this furnace was being used, and they 
said that the lowest line of oiled articles would be about 
eighteen inches distant from the flue. Here, again, it will 
be evident—bearing in mind the exact chemical nature of 
the oil-drying operation—that the conditions were most 
favourable for spontaneous ignition. I was of opinion,, 
that in this case also the oxidizing action (or drying) was 
sufficiently intense spontaneously to produce flame—to 
produce fire, that is to say, among the oiled articles nearest 
the exposed portion of the furnace chimney ; fire which ? 
considering the character of the contents of the room 
would spread -with the greatest rapidity. 
To prevent the occurrence of spontaneous combustion 
in cases where the exigencies of manufacture require the 
employment of fibres or fabrics soaked in vegetable or 
animal oils, such arrangements must be made as shall 
render the accumulation of heat impossible. 
NOTES ON THE QUICKSILVER MINE AND WORKS 
OF V ALL ALT A.* 
The Vallalta quicksilver works are situated in the 
province of Belluno (Venetia), at the south-western ex¬ 
tremity of the Mis valley, where the two torrents, Mis 
and Pezzea, come together, marking the boundary between 
Italy and the Tyrol. The works are about ten miles from 
Agordo, and 2,339 feet above the level of the sea. The- 
cinnabar mine itself lies a short distance from the works, 
on the right bank of the torrent Pezzea. 
The rocks that are met with are chiefly clay-slate, and 
a reddish porphyry ; the latter having broken through the 
former and altered it. Those who desire to study the 
special geological conditions of the mine can consult 
the small geological map accompanying the original me¬ 
moir, which will give a far better idea than a tedious 
* Extracted from a paper in the Bollettino del Club- 
Alpino Italiano for 1871, by Cavaliere G. Antonio de Man- 
zoni, and printed in the Journal of the Society of Arts . 
