THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. [September23, 1871. 
25i 
of brightness. A third party requires a particular shade 
of colour, body and smell combined. Others quarrel 
with the manufacturer if he vary his standard shade of ; 
.colour, smell, etc. The truth is, that these are circum¬ 
stances independent of the proper treatment of the oil. 
The varying qualities of oil require a varied treatment 
>to bring them to one standard of body and drying 
power. If these be the standards to be maintained, the 
others, which after all are only indications that the oil 
lias been manufactured, are of no importance. This ap¬ 
plies to the ordinary process of boiling oil by fire, and I 
<lo not insist but that, if a uniform quantity of oil be 
-•employed, and the same process always pursued, the 
.colour and smell would bo indications of the success of 
that particular process upon that particular oil; but, at 
the present day, the field from which you obtain linseed- 
oil is much wider than it was of old: you cannot always 
buy the oil you prefer, and, of necessity, the mode of 
manufacture you adopt has to some extent to vary. If 
once the idea be thrown over that a high temperature is 
-essential to the preparation of a good boiled-oil, you at 
once obtain modifications of these peculiarities of colour 
.and odour, though the other qualities, body and drying 
power, may be the same, or even increased. 
"With these preconceived notions it is that the new 
process of oil-boiling had and still has to contend, people 
imagining that unless the boiled-oil attains a conven¬ 
tional standard of appearance, it of necessity must be 
bad. One of the advantages of the new process is hereby 
much diminished, since oil-boilers have to adopt expe- 
.-dients to give a colour to the oil which otherwise it 
would not have to nearly the same extent. And to the 
practical man an aim has to be added which fr ds and 
annoys common sense and honesty of purpose, viz. that 
in addition to that of good and improved methods of 
manufacture, there must be sufficient similarity in ap¬ 
pearance to accustomed samples to avoid awakening those 
prejudices against anything new, merely because it is 
new, still largely existing amongst the mechanical part 
of our population. It is the more to be deplored, since 
the colour of white zinc, delicate blues, etc., are much 
deteriorated by the dark oil used for mixing with them. 
I discovered, in the beginning of 1860 that, with suit¬ 
able driei'S, I could obtain an oil which, although it had 
never been raised above the temperature of 228° F., 
nevertheless had the body and the drying power of a 
good boiled-oil. This led me to investigate the subject 
further; although the trade being limited, and the per¬ 
sons engaged in it having acquired a certain reputation 
foiy a good merchantable article, made by processes 
•which they have not unfrequently worked out for them- 
..•selves, they have not the same incentive to seek for im¬ 
provements, or even to adopt them when brought before 
them, as exists in many other manufacturing processes. 
I do not claim any merit as an originator of steam oil¬ 
boiling, for I have reason to believe that it has been 
.practised in Germany for many years past; but, as far 
.-us I am personally concerned, I may state that all I 
know concerning the process I have discovered for my¬ 
self, not even being aware that it was practised by others 
for some years subsequently to my own discovery and 
xise of it. 
Chevreul’s experiments, to which I have previously 
.•alluded, form a good substratum for a disquisition on 
fhis subject. The principle being clearly laid down that 
it is the absorption of oxygen by linseed-oil which 
causes its solidification, it follows that all the substances 
which can be used as driers must be such as are capable 
^of parting with oxygen or dissolving in it, and, being 
.themselves oxidizable in combination, they in that way 
increase its absorptive power. There is a class of driers 
■which act whilst mechanically suspended in the oil, as 
white copperas, etc., for example, increasing its absorp¬ 
tive power by their presence, but leaving no increase of 
(drying power when withdrawn. 
The substances which act catalytically belong, in my 
opinion, to the first class. They part with some of their 
oxygen to this oil, become to a certain extent deoxidized, 
and again coming in contact with air, they reassume 
their primal condition, and are ready to do the same 
work over again. It is this necessity of reoxidation 
which caused the introduction of blowing-machines for 
oil-boiling, when their own proper advantages in rapidly 
giving body to linseed-oil at comparatively low tempe¬ 
ratures were at once, and to me unexpectedly, made 
manifest. These catalytic driers are now generally 
adopted, the effect of their use being simply this (and 
you will see that the result is a great advance upon pre¬ 
vious methods), that by treating the oil with these driers 
under the influence of heat and air, its own absorptive 
powers for oxygen are greatly increased, and remain so 
when the primary incentives to absorption are removed. 
This likewise has to be borne in mind, that what we 
want to do is not to render the oil solid or partially so 
now, but to enable it to become so when exposed to the 
air. 
Many years ago, the late Professor Faraday was con¬ 
sulted as to the possibility of hastening the drying of 
printing inks, so that work might be milled (that is, com¬ 
pressed between zinc plates passed through closely-set 
rollers) with less delay after printing. A fortnight was 
the usual time taken, and, if ordinary driers were used, 
the whole of the ink would skin on the rollers, with many 
other inconveniences. Faraday’s far-sighted sagacity at 
once decided that one solution of the difficulty would be 
by the mechanical introduction of a substance to act as a 
drier which should bo inert till it was exposed to the 
air. As Professor Faraday’s advice and assistance, in a 
research on the same subject for the same firm was of 
material service to me, and, indeed, enabled me to su¬ 
persede the drier in question, I break no confidence by 
stating that it was binoxide of manganese which almost 
without experiment he at once pitched upon. By what 
process of thought he chose this substance I do not know, 
but the fact remains that he did so introduce it, and for, 
I think, between thirty and forty years it was used by 
the same firm. At the Queen’s Bible office they mill 
their work three days after printing, if it prove necessary. 
In order to get the binoxide in a state of division suffi¬ 
ciently fine to mix with printing-ink, he devised a series 
of washing receptacles, like successive stairs, the finer 
particles passing on to the lower vessels, being longer 
suspended than the coarser—a simple yet ingenious 
arrangement, which enabled the ink to be worked with¬ 
out any risk to the plates or formes from grit. 
By properly pursuing this investigation, many other 
substances have been discovered which exercise this 
property in a high degree. Without becoming in any 
way altered, they induce an alteration in the linseed-oil 
subjected to their operation. We may imagine the action 
as similar to that by which spongy platinum explodes a 
mixture of oxygen and hydrogen, or a platinum wire is 
kept red-hot by the vapour of ether. 
Litharge and the other salts of lead perform the same 
office whilst in solution in the oil, and to their presence, 
for the most part, is the dark colour of boiled oil due. 
Where the steam process is used, the oil never reaches a 
sufficiently high temperature to produce carbonization. 
By judiciously mixing one of the substances acting 
catalytically and a lead salt, a drier is obtained, by 
altering the relative proportions of which the boiler is 
enabled to produce any required shade of colour. The 
larger the quantity of litharge, the darker the colour of 
the boiled oil. A lesser proportion of litharge, accom¬ 
panied by a greater quantity of the catalytic drier, gives 
as the product an oil which will dry in the same time, 
and has less colour. These are the principles of oil¬ 
boiling by steam. 
The risk of boiling over, and being the cause of a con¬ 
flagration, was one reason for the distance at which oil¬ 
boiling businesses were formerly kept from towns; the 
abominable smell produced by the evaporation and partial 
