274 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. [September so, 1871. 
pieces of the old skins of oil which may have fallen 
from the sides of the pan. This may be entirely obviated 
.by causing the air to enter the pan through this tap, and 
putting the second tap beyond the air inlet as an outlet 
for the oil. Tho pressure of the air-pump will then 
.suffice to remove any ordinary obstruction ; but if a stop¬ 
page, nevertheless, should occur, nothing remains but to 
probe tho tap with a long, thin rod from the top of the 
pan. Until this simple expedient of letting in the air 
rthrough the oil outlet was adopted, this terrible nuisance 
-was of almost daily occurrence. 
The vapour which comes oft' from hot oil into which 
.air has been blown is so intensely acrid and pungent 
that human nature seems to be incapable of ever getting 
used to it. For my own part, I would much prefer 
•entering a freshly-opened bleaching-powder chamber to 
.an oil-pan, even after the oil has been run off, and the 
pan cooled down. There was no task in the works more 
thoroughly abhorred than that ten minutes to half an 
hour, occasionally longer, during which, with the man¬ 
hole open, the workman was raking and poking between 
the radii of the fans to clear and find the outlet. With 
this now happily occasional exception, and for the few 
.minutes during which the hot oil is being transferred 
from the pan to the tanks, this method of oil-boiling 
produces no disagreeable smell in the vicinity, the fumes 
being carried away with the surplus air pumped through 
the oil, and perfectly consumed, so far as noxious odour 
is concerned, in the furnace of the boiler. Members of 
this Society have frequently the opportunity of witness¬ 
ing the efficacy of the operation of this process during 
.some of the lectures delivered here, the air of this hall 
being kept free from troublesome fumes by a similar 
arrangement. From this paper the chemical questions 
involved must be, for the most part, excluded, as it would 
be scarcely possible for me to enter far into the subject 
without betraying confidence, the driers used, and their 
modus operandi being essentially connected. I may 
.state, however, that the air does not play the part which 
many have assigned to it, and does in reality effect 
mothing towards making the oil a drying one. I have 
boiled linseed-oil with air alone, but without driers, for 
three days consecutively, keeping up a high temperature 
.the whole time, and the resultant boiled-oil has taken 
precisely the same time to dry as the raw oil from which 
it was prepared. The body, however, had so much in- 
-creased that the consistency was more that of a varnish 
fhan an oil. 
If oil be subjected to heat alone for the same space of 
time, without any air except such as comes in contact 
with its surface, there is no such increase in consistence 
;as in the former case; the oil simply becomes more 
.greasy, has less difficulty in penetrating capillary tubes 
i(as, for instance, those of paper, plaster, etc.) than it 
previously had, and has decidedly less drying powers. 
The oil which has been boiled with air is less greasy, 
rind has a greater consistence. To sum up the process 
in a few words, I think we show we have the means at 
band of meeting all the requisites which were stated to 
be necessary. The close apparatus in which the work 
:is performed secures the manufacturer alike from annoy¬ 
ing his neighbours and injuring his own men. The air 
;and heat secure a sufficient amount of body. The driers 
produce any required shade of colour-, the time of 
-drying, t. e. about six hours in summer and eight hours 
in winter, according with the old standard of drying 
power. Oil can be made to dry in much less time, but 
this is not considered to be desirable. The mechanical 
appliances reduce the time of the operation to about 
.one-fourth of that which in former years was thought 
-essential. In the ordinary working day, starting with 
-cold oil and a cold boiler, two batches, of two tons each, 
.can be boiled without causing undue driving of men or 
snachinery. 
Before leaving this part of the subject it may be as 
-svell to note, that for boiled-oil which has to be exported, 
long experience has shown that it is advisable in all cases 
to add to each barrel or drum of boiled-oil a small pro¬ 
portion of raw oil. After a one or two months’ voyage 
the oil becomes brighter than it was when first shipped, 
and the risk of becoming what is called “ fatty,” and not 
free enough in working, is thereby avoided. For a three 
months’ voyage, one gallon of raw linseed may be added 
to each four gallons of boiled-oil with most beneficial 
results, particularly if the boiled-oil be anything under 
one month old. 
Varnishes. 
As you all know, the main uses to which varnishes 
are applied are, to protect the material over which it is 
spread from atmospheric influences, accidental rough 
usage, etc.; to bring out and display more fully the 
varying texture of different woods; and, finally, to give 
a fine gloss or appearance of polish to the surfaces to 
which it is applied. As commonly constituted, an oil 
varnish (and with these alone I propose to deal) consists 
of some hard gum dissolved in linseed oil. This is the 
substance of the varnish, the two being re-dissolved in 
turpentine to afford the means of spreading them out 
in thin layers. As far as regards the ultimate value of 
the varnish, the turpentine is merely so much waste 
material. It may, if it be of inferior quality, injure the 
varnish with which it is mixed, but, however good it 
may be, it can do nothing to benefit or improve a 
varnish which itself is in reality nothing but the mix¬ 
ture in various proportions of some one or more hard 
gums in linseed oil. 
For the convenience of better understanding the 
rationale of the mode of procedure, it will be well if we 
commence our observations at the end instead of begin¬ 
ning of the process. 
Turpentine, being applied for the purpose of thinning 
down the body of the varnish, and that body being, 
when cold, almost solid, has to be added whilst the 
mixture of gum and oil is still hot. The heat causing 
an increased evaporation, and consequently a loss of 
turpentine, the temperature is allowed to get as low as 
can be, consistently with a perfect and complete admix¬ 
ture of the spirit with the matter being secured. This 
is, to some extent, contrary to old-fashioned notions, but 
the varnishes resulting from mixing in the turpentine at 
a high temperature and at a low one being identical, the 
loss of so much evaporated material is not now taken as 
an essential part of the process. We have also one less 
risk of fire, since the whole varnish is now removed far 
from any fire, and out into the open air when practicable, 
before the turpentine is added. The quantity of tur¬ 
pentine required under these circumstances is much less 
than that stated in the various published recipes for var¬ 
nish making. Enough is commonly added to bring the 
whole mixture to a consistence a little stiffer than linseed- 
oil. The loss by evaporation, whilst clearing and ageing 
in tanks, previous to its being sent out, gives it the amount 
of body which you are accustomed to see it have. The 
next thing to consider is the body of the varnish. Time 
would not permit me to give a complete description of the 
various gums which are or may be used; I can do no 
better than refer you to Mr. Neil’s paper for information 
on this part of the subject. There is one gum, however, 
which has come very largely into use since his time, and 
that is the “ kauri,” New Zealand gum. It is rather 
dull in appearance, but it is tolerably hard, and melts at 
so low a temperature that the dust and chips made by 
cleaning the outside of large pieces can be utilized by a 
skilful man, without the gum being coloured by the 
carbonization of the woody matter in it. The varnish 
made from the better qualities of kauri have a very good 
gloss. When dry, they are pale in colour; dry quickly, 
and are not so liable to crack when exposed to the sun as 
better varnishes. After a few months’ exposure to wet, 
however, the whole of the gloss disappears, and, though 
the protecting surface remains, it becomes, through its 
