Chapter XIV: Appendix

NUMBER 1 (See page 1007)
PROFESSOR SILLIMAN’S REPORT ON PETROLEUM

[From “The Early and Later History of Petroleum,” by J. T. Henry,
pages 38–54.]

MESSRS. EVELETH, BISSELL AND REED.

_Gentlemen_:—I herewith offer you the results of my somewhat
extended researches upon the rock-oil, or petroleum, from Venango
County, Pennsylvania, which you have requested me to examine with
reference to its value for economical purposes.

Numerous localities, well known in different parts of the world,
furnish an oily fluid exuding from the surface of the earth,
sometimes alone in “tar springs,” as they are called in the Western
United States; frequently it is found floating upon the surface of
water in a thin film, with rainbow colours, or in dark globules,
that may, by mechanical means, be separated from the fluid on which
it swims.

In some places wells are sunk for the purpose of accumulating the
product in a situation convenient for collection by pumping the
water out. The oil exudes on the shores of lakes and lagoons, or
rises from springs beneath the beds of rivers. Such are the springs
of Baku, in Persia, and the wells of Amiano, in the duchy of Parma,
in Italy. The usual geological position of the rocks furnishing this
natural product is in the coal measures—but it is by no means
confined to this group of rocks, since it has been found in deposits
much more recent, and also in those that are older—but in whatever
deposits it may occur, it is uniformly regarded as a product of
vegetable decomposition. Whether this decomposition has been
effected by fermentation only, or by the aid of an elevated
temperature, and distilled by heated vapour, is perhaps hardly
settled.

It is interesting, however, in this connection to remember that the
distillation, at an elevated temperature, of certain black,
bituminous shales in England and France has furnished large
quantities of an oil having many points of resemblance with naphtha,
the name given to this colourless oil, which is the usual product of
distilling petroleum. The very high boiling point of most of the
products of the distillation of the rockoil from Venango County,
Pennsylvania, would seem to indicate that it was a pyrogenic
(fire-produced) product.

Bitumen, asphaltum, mineral pitch, chapapote, etc., etc., are names
variously given to the more or less hard, black, resinous substance
which is produced usually from the exposure of petroleum to the air,
and is found either with or without the fluid naphtha or petroleum.
The most remarkable examples of the occurrence of these substances,
so intimately connected with the history of rock-oil, are the Lake
Asphaltites of the Dead Sea, so memorable in history, the well-known
Bitumen Lake of Trinidad, and the deposits of mineral pitch or
chapapote in Cuba. In one of the provinces of India, vast quantities
of petroleum are annually produced, the chief consumption being
local, for fuel and lights, but a portion is also exported to Europe
for the production of naphtha. In the United States, many points on
the Ohio and its tributaries are noted as producing this oil; nearly
all of them within the coal measures. A detailed history of these
various localities can be found recorded in books of science, and
their repetition here would be out of place.

GENERAL CHARACTER OF THE CRUDE PRODUCT

The crude oil, as it is gathered on your lands, has a dark brown
colour, which, by reflected light, is greenish or bluish. It is
thick even in warm weather—about as thick as thin molasses. In very
cold weather it is somewhat more stiff, but can always be poured
from a bottle even at 15° below zero. Its odour is strong and
peculiar, and recalls to those who are familiar with it the smell of
bitumen and naphtha. Exposed for a long time to the air, it does not
thicken or form a skin on its surface, and in no sense can it be
called a drying oil. The density of the crude oil is .882, water
being 1.000. It boils only at a very high temperature, and yet it
begins to give off a vapour at a temperature not greatly above that
of boiling water. It takes fire with some difficulty and burns with
an abundant smoky flame. It stains paper with the appearance of
ordinary fat oils, and feels smooth and greasy between the fingers.
It is frequently used in its crude state to lubricate coarse
machinery. In chemical characters, it is entirely unlike the fat
oils. Most of these characters are common to petroleum from various
places. In one important respect, however, the product of your lands
differs from that obtained in other situations, that is, it does
not, by continued exposure to the air, become hard and resinous like
mineral pitch or bitumen. I have been informed by those who have
visited the locality, that on the surface of the earth above the
springs which furnish your oil there is no crust or deposit of this
sort such as I have seen in other situations where petroleum or
mineral tar is flowing. This difference will be seen to be of
considerable importance, as it is understood and represented that
this product exists in great abundance upon your property, that it
can be gathered wherever a well is sunk in the soil, over a great
number of acres, and that it is unfailing in its yield from year to
year. The question naturally arises, Of what value is it in the
arts, and for what uses can it be employed? These researches answer
these inquiries.

EXAMINATION OF THE OIL

To determine what products might be obtained in the oil, a portion
of it was submitted to fractional distillation.[82] The temperature
of the fluid was constantly regulated by a thermometer, the heat
being applied first by a water bath, and then by a bath of linseed
oil. This experiment was founded upon the belief that the crude
product contained several distinct oils, having different boiling
points. The quantity of material used in this experiment was 304
grammes. The thermometer indicated the degrees of the Centigrade
scale, but, for convenience, the corresponding degrees of
Fahrenheit’s scale are added. The water bath failed to distil any
portion of the oil at 100° C. (= 212° F.), only a small quantity of
acid water came over. An oil bath, linseed oil, was then
substituted, and the temperature was regularly raised by slow
degrees until distillation commenced. From that point the heat was
successively raised by stages of ten degrees, allowing full time at
each stage for complete distillation of all that would rise at that
temperature before advancing to the next stage. The results of this
tedious process are given in the annexed table—304 grammes of crude
oil, submitted to fractional distillation, gave

TEMPERATURE QUANTITY
1st Prod. at 100° C. = 213° F.(acid water) 5 gms.
2nd Prod. at 140° C. to 150° C.= 284° to 302° F. 26 gms.
3rd Prod. at 150° C. to 160° C.= 302° to 320° F. 29 gms.
4th Prod. at 160° C. to 170° C.= 320° to 388° F. 38 gms.
5th Prod. at 170° C. to 180° C.= 338° to 367° F. 17 gms.
6th Prod. at 180° C. to 200° C.= 356° to 392° F. 16 gms.
7th Prod. at 200° C. to 220° C.= 392° to 428° F. 17 gms.
8th Prod. at 220° C. to 270° C.= 428° to 518° F. 12 gms.
Whole quantity distilled by this method 160 gms.
———
Leaving residue in the retort 144 gms.
———
Original quantity 304 gms.

_Product No. 1_, as above remarked, was almost entirely water, with
a few drops of colourless oil, having an odour similar to the
original fluid, but less intense.

_Product No. 2_ was an oil perfectly colourless, very thin and
limpid, and having an exceedingly persistent odour, similar to the
crude oil, but less intense.

_Product No. 3_ was tinged slightly yellow, perfectly transparent,
and apparently as limpid as the second product, with the same odour.

_Product No. 4_ was more decidedly yellowish than the last, but was
in no other respect distinguishable from it.

_Product No. 5_ was more highly coloured, thicker in consistence,
and had a decided empyreumatic odour.

_Product No. 6._ This and the two subsequent products were each more
highly coloured and denser than the preceding. The last product had
the colour and consistency of honey, and the odour was less
penetrating than that of the preceding oils. The mass of crude
product remaining in the retort (equal 47.4 per cent.) was a dark,
thick, resinous-looking varnish, which was so stiff when cold that
it could be inverted without spilling. This showed no disposition to
harden or skin over by exposure to the air. The distillation was
arrested at this point in glass, by our having reached the limit of
temperature for a bath of linseed oil. The _density_ of the several
products of this distillation shows a progressive increase, thus:

DENSITY
No. 2 733
No. 3 752
No. 4 766
No. 5 776
No. 6 800
No. 7 848
No. 8 854

To form an idea of the comparative density of these several
products, it may be well to state that sulphuric ether, which is one
of the lightest fluids known, has a density of .736, and alcohol,
when absolutely pure, .800.

The _boiling points_ of these several fluids present some anomalies,
but are usually progressive, thus, No. 2 gave signs of boiling at
115° C. (= 239° F.), and boiled vigorously and remained constant at
225° C. to 228° C. (= 437° to 442° F.). No. 3 began to boil 120° (=
248° F.), rose to 270° (= 518° F.), where it remained constant. No.
4 began to vapourise at 140° (= 284° F.), rose to 290° (= 554° F.),
where it remained constant. On a second heating the temperature
continued to rise, and passed 305° (= 581° F.). No. 5 gave
appearance of boiling at 160° (= 320° F.), boiling more vigorously
as the heat was raised, and was still rising at 308° (= 581° F.).
No. 6 commenced boiling at 135° (= 275° F.), boiled violently at
160° (= 320° F.), and continued rising above the range of the
mercurial thermometer. No. 7 commenced ebullition at the same
temperature as No. 6, and rose to 305° (= 581° F.), where the
ebullition was not very active. Much time was consumed in obtaining
these results. We infer from them that the rock-oil is a mixture of
numerous compounds, all having essentially the same chemical
constitution, but differing in density and boiling points, and
capable of separation from each other, by a well-regulated heat.

The uncertainty of the boiling points indicates that the products
obtained at the temperatures named above were still mixtures of
others, and the question forces itself upon us, whether these
several oils are to be regarded as _educts_ (i. e., bodies
previously existing, and simply separated in the process of
distillation), or whether they are not rather produced by the heat
and chemical change in the process of distillation. The continued
application of an elevated temperature alone is sufficient to effect
changes in the constitution of many organic products, evolving new
bodies not before existing in the original substance.

PROPERTIES OF THE DISTILLED OILS

Exposed to the severest cold of the past winter, all the oils
obtained in this distillation remained fluid. Only the last two or
three appeared at all stiffened by a cold of 15° below zero, while
the first three or four products of distillation retained a perfect
degree of fluidity. Exposed to air, as I have said, they suffer no
change. The chemical examination of these oils showed that they were
all composed of carbon and hydrogen, and probably have these
elements in the same numerical relation. When first distilled they
all had an acid reaction, due to the presence of a small quantity of
free sulphuric acid, derived from the crude oil. This was entirely
removed by a weak alkaline water, and even by boiling on pure water.
Clean copper remained untarnished in the oil which had thus been
prepared, showing its fitness for lubrication, so far as absence of
corrosive quality is concerned. The oils contain no oxygen, as is
clearly shown by the fact that clean potassium remains bright in
them. Strong _sulphuric acid_ decomposes and destroys the oil
entirely. _Nitric acid_ changes it to a yellow, oily fluid, similar
to the changes produced by nitric acid on other oils.
_Hydrochloric_, _chromic_, and _acetic acids_ do not affect it.
_Litharge_ and other metallic oxyds do not change it, or convert it
in any degree to a drying oil. _Potassium_ remains in it unaffected,
even at a high temperature. _Hydrates of potash_, _soda_, and _lime_
are also without action upon it. _Chloride of calcium_ and many
other salts manifest an equal indifference to it. Distilled with
_bleaching powders_ (chloride of lime) and water in the manner of
producing chloroform, the oil is changed into a product having an
odour and taste resembling chloroform. Exposed for many days in an
open vessel, at a regulated heat below 212°, the oil gradually rises
in vapour, as may be seen by its staining the paper used to cover
the vessel from dust, and also by its sensible diminution. Six or
eight fluid ounces, exposed in this manner in a metallic vessel for
six weeks or more, the heat never exceeding 200°, gradually and
slowly diminished, grew yellow, and finally left a small residue of
dark brown, lustrous-looking resin, or pitchy substance, which in
the cold was hard and brittle. The samples of oil employed were very
nearly colourless. This is remarkable when we remember that the
temperature of the distillation was above 500° F. The oil is nearly
insoluble in pure alcohol, not more than 4 or 5 per cent. being
dissolved by this agent. In ether the oil dissolves completely, and
on gentle heating is left unchanged by the evaporisation of the
ether. India-rubber is dissolved by the distilled oil to a pasty
mass, forming a thick, black fluid which, after a short time,
deposits the India-rubber. It dissolved a little amber, but only
sufficient to colour the oil red. It also dissolves a small portion
of copal in its natural state, but after roasting, the copal
dissolves in it as it does in other oils.

USE FOR GAS-MAKING

The crude oil was tried as a means of illumination. For this
purpose, a weighed quantity was decomposed, by passing it through a
wrought-iron retort filled with carbon, and ignited to full redness.
The products of this decomposition were received in a suitable
apparatus. It produced nearly pure carburetted hydrogen gas, the
most highly illuminating of all the carbon gases. In fact, the oil
may be regarded as chemically identical with illuminating gas in a
liquid form. The gas produced equalled ten cubic feet to the pound
of oil. It burned with an intense flame, smoking in the ordinary gas
jet, but furnishing the most perfect flame with the Argand burner.

These experiments were not prosecuted further, because it was
assumed that other products, now known and in use, for gas-making,
might be employed at less expense for this purpose, than your oil.
Nevertheless, this branch of inquiry may be worthy of further
attention.

DISTILLATION AT A HIGHER TEMPERATURE

The results of the distillation at a regulated temperature in glass
led us to believe that in a metallic vessel, capable of enduring a
high degree of heat, we might obtain a much larger proportion of
valuable products. A copper still, holding five or six gallons, was
therefore provided, and furnished with an opening, through which a
thermometer could be introduced into the interior of the vessel.
Fourteen imperial quarts (or, by weight, 560 ounces) of the crude
product were placed in this vessel, and the heat raised rapidly to
about 280° C. (= 536° F.), somewhat higher than the last temperature
reached in the first distillation. At this high temperature the
distillation was somewhat rapid, and the product was easily
condensed without a worm. The product of the first stage was 130
ounces (or over 28 per cent.), of a very light-coloured thin oil,
having a density of .792. This product was also acid, and as before,
the acid was easily removed by boiling with fresh water. The
temperature was now raised to somewhat above 300° C. (= 572° F.),
and 123 ounces more distilled, of a more viscid and yellowish oil,
having a density of .865. This accounts for over 43 per cent. of the
whole quantity taken. The temperature being raised now above the
boiling point of mercury, was continued at that until 170 ounces, or
over 31 per cent., of a dark brown oil had been distilled, having a
strong empyreumatic odor. Upon standing still for some time, a dark
blackish sediment was seen to settle from this portion, and on
boiling it with water the unpleasant odour was in a great degree
removed, and the fluid became more light-coloured and perfectly
bright. (It was on a sample of this that the photometric experiments
were made.) The next portion, distilled at about 700° F., gave but
about 17 ounces, and this product was both lighter in colour and
more fluid than the last. It now became necessary to employ dry
hickory wood as a fuel, to obtain flame and sufficient heat to drive
over any further portions of the residue remaining in the alembic.

It will be seen that we have already accounted for over 75 per cent.
of the whole quantity taken. There was a loss on the whole process
of about 10 per cent. made up, in part, of a coaly residue that
remained in the alembic, and partly of the unavoidable loss
resulting from the necessity of removing the oil twice from the
alembic, during the process of distillation, in order to change the
arrangements of the thermometer, and provide means of measuring a
heat higher than that originally contemplated.

About 15 per cent. of a very thick, dark oil completed this
experiment. This last product, which came off slowly at about 750°
F., is thicker and darker than the original oil, and when cold, is
filled with a dense mass of pearly crystals. These are paraffine, a
peculiar product of the destructive distillation of many bodies in
the organic kingdom. This substance may be separated, and obtained
as a white body, resembling fine spermaceti, and from it beautiful
candles have been made. The oil in which the crystals float is of a
very dark colour, and by reflected light is blackish green, like the
original crude product. Although it distills at so high a
temperature, it boils at a point not very different from the denser
products of the first distillation. The paraffine, with which this
portion of the oil abounds, does not exist ready-formed in the
original crude product; but it is a result of the high temperature
employed in the process of distillation, by which the elements are
newly arranged.

I am not prepared to say, without further investigation, that it
would be desirable for the company to manufacture this product in a
pure state, fit for producing candles (a somewhat elaborate chemical
process); but I may add that, should it be desirable to do so, the
quantity of this substance produced may probably be very largely
increased by means which it is now unnecessary to mention.

Paraffine derives its name from the unalterable nature of the
substance, under the most powerful chemical agents. It is white, in
brilliant scales of a greasy lustre; it melts at about 116°, and
boils at over 700° F.; it dissolves in boiling alcohol and ether,
and burns in the air with a brilliant flame. Associated with
paraffine are portions of a very volatile oil, _eupione_, which
boils at a lower temperature, and by its presence renders the
boiling point of the mixture difficult to determine. I consider this
point worthy of further examination than I have been able at present
to give it, i.e., whether the last third, and possibly the last
half, of the petroleum, may not be advantageously so treated as to
produce from it the largest amount of paraffine which it is able to
produce.

The result of this graduated distillation, at a high temperature, is
that we have obtained over 90 per cent. of the whole crude product
in a series of oils, having valuable properties, although not all
equally fitted for illumination and lubrication.

A second distillation of a portion of the product which came over in
the later stages of the process (a portion distilled at about 650°
F., and having a high colour), gave us a thin oil of density about
.750, of light yellow colour and faint odour.

It is safe to add that, by the original distillation, about 50 per
cent. of the crude oil is obtained in a state fit for use as an
illuminator without further preparation than simple clarification by
boiling a short time with water.

DISTILLATION BY HIGH STEAM

Bearing in mind that by aid of high steam, at an elevated
temperature, many distillations in the arts are affected which
cannot be so well accomplished by dry heat, I thought to apply this
method in case of the present research. Instances of this mode of
distillation are in the new process for Stearine candles, and in the
preparation of rosin oil. I accordingly arranged my retort in such a
manner that I could admit a jet of high steam into the boiler, and
almost at the bottom of the contained petroleum. I was, however,
unable to command a jet of steam above 275° to 290° F., and although
this produced abundant distillation, it did not effect a separation
of the several products, and the fluid distilled had much the same
appearance as the petroleum itself, thick and turbid. As this trial
was made late in the investigation, I have been unable to give it a
satisfactory issue, chiefly for want of steam of a proper
temperature. But I suggest, for the consideration of the company,
the propriety of availing themselves of the experience already
existing on this subject, and particularly among those who are
concerned in the distillation of rosin oil—a product having many
analogies with petroleum in respect to its manufacture.

USE OF THE NAPHTHA FOR ILLUMINATION

Many fruitless experiments have been made in the course of this
investigation which it is needless to recount. I will, therefore,
only state those results which are of value.

1. I have found that the only lamp in which this oil can be
successfully burned is the camphene lamp, or one having a button to
form the flame, and an external cone to direct the current of air,
as is now usual in all lamps designed to burn either camphene, rosin
oil, sylvic oil, or any other similar product.

2. As the distilled products of petroleum are nearly or quite
insoluble in alcohol, burning fluid (i. e., a solution of the oil in
alcohol) cannot be manufactured from it.

3. As a consequence, the oil cannot be burned in a hand lamp, since,
with an unprotected wick, it smokes badly. Neither can it be burned
in a Carcel’s mechanical lamp, because a portion of the oil being
more volatile than the rest, rises in vapour on the elevated wick
required in that lamp, and so causes it to smoke.

I have found all the products of distillation from the copper still
capable of burning well in the camphene lamp, except the last third
or fourth part (i.e., that portion which came off at 700° F. and
rising, and which was thick with the crystals of paraffine). Freed
from acidity by boiling on water, the oils of this distillation
burned for twelve hours without injuriously coating the wick, and
without smoke. The wick may be elevated considerably above the level
required for camphene, without any danger of smoking, and the oil
shows no signs of crusting the wick tubes with a coating of rosin,
such as happens in the case of camphene, and occasions so much
inconvenience. The light from the rectified naphtha is pure and
white, without odour. The rate of consumption is less than half that
of camphene, or rosin oil. The Imperial pint, of 20 fluid ounces,
was the one employed—a gallon contains 160 such ounces. A camphene
lamp, with a wick one inch thick, consumed of rectified naphtha in
one hour, 1¾ ounces of fluid. A Carcel’s mechanical lamp of ⅞–inch
wick, consumed of best sperm oil, per hour, 2 ounces. A “Diamond
Light” lamp, with “sylvic oil,” and a wick 1½–inch diameter,
consumed, per hour, 4 ounces.

I have submitted the lamp burning petroleum to the inspection of the
most experienced lampists who were accessible to me, and their
testimony was, that the lamp burning this fluid gave as much light
as any which they had seen, that the oil spent more economically,
and the uniformity of the light was greater than in camphene,
burning for twelve hours without a sensible diminution, and without
smoke. I was, however, anxious to test the amount of light given,
more accurately than could be done by a comparison of opinions. With
your approbation I proceeded therefore to have constructed a
_photometer_, or apparatus for the measurement of light, upon an
improved plan. Messrs. Grunow, scientific artists of this city,
undertook to construct this apparatus, and have done so to my entire
satisfaction. This apparatus I shall describe elsewhere—its results
only are interesting here. By its means I have brought the petroleum
light into rigid comparison with the most important means of
artificial illumination. Let us briefly recapitulate the results of
these

PHOTOMETRIC EXPERIMENTS

The _unit_ adopted for comparison of intensities of illumination is
Judd’s Patent Sixes Sperm Candle.

The sperm oil used was from Edward Mott Robinson, of New Bedford—the
best winter sperm remaining fluid at 32° F. The colza oil and
Carcel’s lamps were furnished by Dardonville, lampist, Broadway, New
York. The gas used was that of the New Haven Gas Light Co., made
from best Newcastle coal, and of fair average quality.

The distance between the standard candle, and the illuminator sought
to be determined, was constantly 150 inches—the photometer traversed
the graduated bar in such a manner as to read, at any point where
equality of illumination was produced, the ratio between the two
lights. I quote only single examples of the average results, and
with as little detail as possible, but I should state that the
operation of the photometer was so satisfactory that we obtained
constantly the same figures when operating in the same way, evening
after evening, and the sensitiveness of the instrument was such that
a difference of one-half inch in its position was immediately
detected in the comparative illumination of the two equal discs of
light in the dark chamber. This is, I believe, a degree of accuracy
not before obtained by a photometer.

TABLE OF ILLUMINATING POWER OF VARIOUS ARTIFICIAL LIGHTS COMPARED WITH
JUDD’S PATENT CANDLES AS A UNIT

SOURCE OF LIGHT RATIO TO CANDLE—1 Gas burning in Scotch fish-tail tips, 4 feet to the hour 1 : 5.4 Gas burning in Scotch fish-tail tips, 6 feet to the hour 1 : 7.55 Gas burning in Cornelius fish-tail tips, 6 feet to the hour 1 : 6.3 Gas burning in English Argand burner, 10 feet to the hour 1 : 16 Rock-oil, burning in 1–inch wick camphene lamp, consuming 1¾ ounces of fluid to the hour 1 : 8.1 Carcel’s mechanical lamp, burning best sperm oil, 2 ounces of fluid to the hour, wick ⅞ of an inch 1 : 7.5 Carcel’s mechanical lamp, burning best sperm oil, 2 ounces of colza oil to the hour, wick of ⅞ an inch 1 : 7.5 Camphene lamp (same size as rock-oil above) burning best camphene, 4 fluid ounces per hour 1 : 11 “Diamond Light” by “sylvic oil,” in 1½–inch wick, 4 ounces per hour 1 : 8.1

From this table it will be seen that the rock-oil lamp was somewhat
superior in illuminating power to Carcel’s lamp of the same size,
burning the most costly of all oils. It was also equal to the
“Diamond Light” from a lamp of one-half greater power, and
consequently is superior to it in the same ratio in lamps of equal
power. The camphene lamp appears to be about one-fifth superior to
it, but, on the other hand, the rock-oil surpasses the camphene by
more than one-half in economy of consumption (i.e., it does not
consume one-half so much fluid by measure), and it burns more
constantly. Compared with the sylvic oil and the sperm, the rock-oil
gave on the ground glass diaphragm the whitest disc of illumination,
while in turn the camphene was whiter than the rock-oil light. By
the use of screens of different coloured glass, all inequalities of
_colour_ were compensated in the use of the photometer, so that the
intensity of light could be more accurately compared. Compared with
gas, the rock-oil gave more light than any burner used except the
costly Argand consuming ten feet of gas per hour. To compare the
_cost_ of these several fluids with each other, we know the price of
the several articles, and this varies very much in different places.
Thus, gas in New Haven costs $4 per 1,000 feet, and in New York
$3.50 per 1,000, in Philadelphia $2.00 per 1,000, and in Boston
about the same amount.

Such sperm oil as was used costs $2.50 per gallon, the colza about
$2, the sylvic oil 50 cents, and the camphene 68 cents; no price has
been fixed upon for the rectified rock-oil.

I cannot refrain from expressing my satisfaction at the results of
these photometric experiments, since they have given the oil of your
company a much higher value as an illuminator than I had dared to
hope.

USE OF THE ROCK-OIL AS A LUBRICATOR FOR MACHINERY

A portion of the rectified oil was sent to Boston to be tested upon
a trial apparatus there, but I regret to say that the results have
not been communicated to me yet. As this oil does not gum or become
acid or rancid by exposure, it possesses in that, as well as in its
wonderful resistance to extreme cold, important qualities for a
lubricator.