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Volume 6, 1873
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Art. XLIV.—Notes upon the Mineral Oils of New Zealand.

[Read before the Wellington Philosophical Society, 16th January, 1874.]

Abounding, as this colony does, in carbonaceous deposits, mineralized through all the stages of lignite, brown coals, bituminous coals, and anthracite, it is only reasonable to suppose that mineral oils should also occur in it; and indeed oils of this nature have long been known to exist here in small quantity, as films upon the surface of the water of certain springs, or wells sunk to a little depth; but it was only in the year 1866 that the attention of those in a position to give it effect was directed towards ascertaining the precise character of these oils, and the prospects of their occurrence in quantity. *

In that year samples were forwarded to the Colonial Laboratory for analysis, both from the eastern and western sides of the North Island, and the results of their analysis, together with geological reports upon the nature of the country where they were procured, were duly published in the Annual Report for 1866–7, issued by the Geological Survey Department.

Since then further samples have been examined by me from the East Coast, and, though the results obtained upon them have been furnished to the persons by whom they were respectively contributed, and have been besides published in a brief manner in our local papers, still I do not think they have that degree of publicity which the importance of the subject demands for them; nor yet do I think they have that degree of concentration necessary for their easy comprehension by anyone anxious to learn them, as they are interspersed throughout so many publications. In the hope, therefore, of putting all that has been elicited concerning the nature of these oils in a form suitable for those anxious to be informed on this matter, I have prepared this paper.

Before I enter further into this subject I will remind anyone who may need it that these petroleums are simply hydrocarbons, or hydrogen in combination with carbon in different proportions, and every petroleum is a mixture of a great number of such hydrocarbons; and generally, according to the proportion of hydrogen to the carbon of any petroleum, so is its density. As

[Footnote] * N.Z. Gazette, 29th June, 1866. Geol. Rept., 1866–7, p. 8. Col. Mus. and Lab. Repts., 1867, p. 19.

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a rule, the more carbonaceous the oil, the greater its specific gravity and the higher its volatilizing point.

Petroleums are, as a rule, mixtures of hydrocarbon oils differing very greatly in density and consequently in volatilizing points, charged more or less with paraffin—a hydrocarbon oil solid at common temperatures; and also with bituminous or pitch matters, to which last they owe their colour; and it has been found that with most or all our petroleums their lightest and their heaviest oils are unfit for the highest use we can put them to—that is, for illuminating purposes; consequently they are separated from the rest by fractional distillation, and the oils of intermediate density thus obtained only require treatment with sulphuric acid and an alkali successively, and to be finally re-distilled, to fit them for their destined use, the acid being used to clear the impurities contained in the oil, and so to convert them into such a form that they can be removed from the oil by water.

It will be observed how very simple the process of refining these oils is, all that is required being steadiness in the distillation, the use of certain chemicals in quantities proportionate to the amount and nature of the impurities present in the oil operated upon, and the proper division of the distillate. I may state that these oils are far easier to purify than those obtained by the destructive distillation of any kind of carbonaceous substance.

Having thus stated briefly the nature of these oils, and the means necessary to fit them for illuminating purposes, I will now proceed with the subject of this paper, in the hope that, by the aid of the foregoing remarks, I may be understood throughout, even by those who may have been hitherto unacquainted with the manufacture in question.

The oils I have had the opportunity of examining up to this time are of three distinct kinds, and from as many distinct localities:


The Sugar Loaves, in Taranaki Province.


Poverty Bay, on the east coast of the Province of Auckland.


Manutahi—Waiapu, East Cape.

1.The first, that from the Sugar Loaves, is a very remarkable oil, its specific gravity being no less that .960 to .964 at 60° Fah., water at 1. The heaviest petroleum mentioned by Gesner, .927, has a specific gravity of about .930.

All the various samples which have been submitted have the same physical characters, having a dirty green colour by reflected light and being opaque, unless examined in thin films, when it has a deep red colour by transmitted light.

At 60° Fah. it is quite liquid, and though at lower temperatures it has considerable consistency, yet when reduced to 5° Fah. it does not become solid.

It has a mawkish but not unpleasant odour, being very different in this

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respect from most rock oils, and is especially free from all traces of sulphuretted hydrogen gas.

Minute flakes of a white substance float in the oil, and are gradually deposited when it is allowed to remain quiet at a low temperature, nearly the whole of this solid substance becoming dissolved when the oil is gently heated.

The temperature at which the oil boils is 340° Fah., and it does not appear to evaporate at ordinary temperature, for when exposed to the air it remains unchanged, neither thickening nor acquiring a skin on the surface.

Its temperature requires to be raised to 260° Fah. before its vapour inflames.

This oil differs from petroleum oils generally in not containing paraffin. In this respect it resembles a so-called surface oil occurring in Santa Barbara County, California. These oils also agree in being of very similar density.

Details of the results of the distillation of a small quantity of this oil have been given in a special report by Dr. Hector, but since then I have had the opportunity given me of operating upon larger samples, and I have thus obtained further results which could not well be observed otherwise.

A large quantity of the oil was distilled very slowly until 82 per cent. of volume of the charge had passed over. The residual matter left in the retort set very hard on cooling to 60° Fah. It had the appearance of pitch, and would have yielded a further quantity of solid and liquid distillates if needed. The density of the several portions of the oil obtained was as follows:—

[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

NO. Volume of Distillate Upon Charge. Specific Gravity.
1 2 per cent. .880
2 5.5 " .888
3 5.5 " .900
4 4 " .910
5 8 " .917
6 8 " .926
7 12 " .938
8 12 " .930
9 13 " .898
10 4 " .908
11 8 " .938

The total amount of oil distilled over was therefore 82 per cent. upon the charge taken, and the amount of residual matter left, 18 per cent. This was a kind of pitch, intensely black, and solidifying to a very hard mass at common temperatures. By destructive distillation it would, of course, yield further oily and solid products.

On an examination of the columns just given, it will be observed that the products of the distillation of this oil do not constantly increase in density as the process of distillation goes on, but that, while they increase in density with

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an appearance of uniformity for the first seven distillates, at the 8th, 9th, and 10th, or when about half the oil has been drawn over, these distillates drop very considerably in density, or from .938 to .930, .898, and .908.

I may state that the temperature of the contents of the retort could not have been lower at this stage than at the one just previous.

We may properly attribute this reversion of density to the splitting up of some oil or oils in the retort into oils lighter and heavier than themselves; and this view is supported by the fact that these two distillates afforded me, to successive fractional distillation, oils very much lighter than any which I could obtain by treating in a similar manner the first distillates of the crude oil. Thus, half an ounce of the lightest oil I obtained from the first four distillates had a specific gravity of .8574 at 60° Fah., while the same quantity obtained from the ninth and and tenth distillates had a specific gravity of .7706 at 60° Fah. The latter sample has a much lighter and more agreeable odour than the other.

The heaviest oil I could obtain from this petroleum had a specific gravity of .964

Those oils having higher specific gravities than .950 solidified at 12° Fah.

The last portion of the oil distilled over solidified in the condenser. This portion, on being examined, yielded whitish crystals, which fused at a temperature of about 170° Fah. They are therefore, no doubt, naphthaline. I do not think this substance exists in the crude oil; it is most probably a product of some change wrought upon it by the heat employed in the process. Probably the light oil—that with a specific gravity of .770—and this napthaline are formed simultaneously.

To test the applicability of this oil for illuminating purposes I took a further quantity of it, and retorted over 40 per cent. I then treated the distillate with 3 per cent. of sulphuric acid, shook the mixture well about, washed away the tarry matters resulting, and agitated the oil with 2 per cent. of soda of the strength generally used for purposes of this kind. The oil removed from the soda was then re-distilled until oil equal to 30 per cent. of the quantity originally taken had distilled over. This oil had a specific gravity of .904. Its colour was a pale yellow. It burns in a kerosene lamp with a dull sluggish flame of small volume, and I question whether it can be made to substitute the kerosene now used here.

The fact, however, is an important one, that by a course of fractional and apparently destructive distillation, the petroleum in part breaks up into a series of oils considerably lighter than any present in the natural oil, and into heavy oils, naphthaline, and tarry matters. By the employment of apparatus appropriate for such a process as this, it is not improbable that a portion of a certain charge of this oil could be so far improved as to be capable of use for

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illuminating purposes; but whether this could be attained at a cost sufficiently low to allow a profit on the process is as yet doubtful.

The principal use, however, for which this petroleum appears best suited, is that of a lubricant, and this on account of its low freezing and high volatilizing points, and its exceedingly slight affectibility by air at common temperatures.

2. The next oil I have to describe is that from Poverty Bay, East Coast of Auckland Province.

It is quite different in constitution from the Taranaki oil, being a true paraffin oil, as are most, if not all, of those from the United States of America. It most resembles the Canadian oil.

The following are the characters observed for numerous samples of it:—

Opalescent and thickly interspersed with minute flaky particles of a white colour. By warming the oil gently these particles subside, and the oil manifests the following characters:—Translucent in masses of considerable thickness. Colour red by transmitted, and blackish-green by reflected light. Flows readily, and gives off the usual odour of crude petroleum. Its boiling point at 30 inches barometric pressure varies from 289°—291° Fah. The temperature at which its vapour inflames is from 230° to 233° Fah., and its specific gravity varies from .864 to .871 at 60° Fah. It passes into a jelly-like mass at 50° Fah., a circumstance owing to the quantity of paraffin dissolved in the oil.

The petroleum, carefully distilled, afforded the following results:—

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No. Volume of Distillate Upon Charge. Specific Gravity.
1 2.5 colourless .809
2 16 nearly colourless .826
3 16 pale yellow. .836
4 19 dark yellow. .850
5 11 dark yellow. .855
6 8 brown; solid at 40° Fah. .864
7 21.25 paraffin oil.
6.25—Residue in retort, pitch.

Nos. 1, 2, 3, 4, and 5 of these distillates were mixed and purified with 2 per cent. of sulphuric acid and 2 per cent, of soda solution successively, then re-distilled.

The first 2 per cent. drawn over had a specific gravity of .805. This was kept separate from the other, and the distillation continued until the distillates respectively had a specific gravity of .838 (No. 3), or 36° Baume; this being the density of the lamp oil obtained from the Canadian petroleum, to

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which, as I have before observed, this oil approximates most nearly of any of those from America.

The yield of oil of this gravity was 55 per cent. of the original charge by volume. The first portion of this—30 per cent.—was colourless; the remainder had a feeble tinge of yellow, which deepened a few shades in a week.

A portion of this oil was tested for illuminating purposes in an ordinary kerosene lamp, and was found to burn with a voluminous clear white flame, which was maintained very steadily until but little of the oil remained unconsumed in the well of the lamp used.

A further experiment upon this petroleum showed that by three successive distillations, and treatment with acids and alkalies, about 65 per cent. of an oil could be obtained from it, having a specific gravity of .843, and burning with a good flame in lamps of this kind, although containing paraffin in some quantity. Most, if not all of our kerosenes, however, contain paraffin in greater quantity than the oil in question, so that I should consider the presence of a little paraffin no serious objection to the oil.

These results then show that about 65 per cent. of this oil may be obtained sufficiently light for use in our ordinary kerosene lamps. In this 65 per cent. I have included the “feints” in the very lightest oils of this petroleum, and I do not see why I should throw them out, as our kerosenes are charged with oils still lighter than these, and in greater quantity, as I shall presently show. However, from 1 to 1 ½ per cent. taken off does not affect the value of the oil at all seriously.

I will conclude my note on this oil by stating that the lightest and the heaviest oils I have yet obtained from it are of a specific gravity of .7289 and .885 respectively, at 50° Fah.

3. The last of these petroleums is that from Manutahi, on the Waiapu River. The first sample was forwarded to the Colonial Laboratory by Major Ropata.

It is the lightest oil of any I have yet tested, occurring in this country in a native state. The following are its special characters:—Colour pale brown, nearly or quite transparent; does not manifest a green-black colour by reflected light. Flows with great freedom; has the odour of kerosene. Specific gravity, .8294 at 60° Fah. Burns well in a kerosene lamp for some time.

These characters show the oil to be of a very superior class, indeed so very superior that I at first suspected it had been “improved” by some one. However, further operations upon it soon showed that that was not the case. Thus it contains at most but traces of paraffin, as it does not acquire any increased consistency when lowered in temperature to + 8° Fah., while all our kerosenes now in the market solidify at this temperature, and the other

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Poverty Bay petroleums at considerably higher temperatures. It is obvious, therefore, that this sample is not a mixture of the two, as naturally suggests itself, but a bonâ fide production. I believe it to be the former oil re-distilled, but in a natural way.

The oil, submitted to distillation, afforded the following results:—

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40 per cent. colourless oil at specific gravity .800
33" pale coloured oil " .826
12.5 " yellow " " .840
6.25 " .860
4.25 " .870
96.00 —Total distilled off.
4.0 —Residue in retort.

The residue is oil saturated with paraffin. It sets at common temperatures.

The only oils containing paraffin are those of specific gravity .860 and .870. It will thus be seen that 85.5 per cent. of the distillate is uncontaminated with this substance; so that, allowing 1 ½ per cent. for light oils, we have 84 per cent. of an oil obtainable from this petroleum fit for use in our kerosene lamps, and this by a single distillation and without subjecting it to the action of any purifying agents.

By two more successive distillations of the first two samples I obtained oil amounting to 66 per cent. upon the crude oil, and having a specific, gravity of .811, or that of common kerosene. This was almost colourless, and had not, I believe, acquired any darker shade since it was distilled. Two per cent. of the lightest oils have been removed from this sample.

The lightest oils I have yet distilled from this petroleum by three successive distillations have a specific gravity of .778, .770, and .754 respectively. The total quantity amounted to 4 per cent. upon the sample taken. The heaviest oil obtained has a specific gravity of .871; its quantity, 2 per cent. upon oil taken. This is, therefore, certainly a first-class oil.

For purpose of comparison, I now detail the results of my examination of a brand of kerosene much used here—a good kerosene, burning well, and still a safe one. Taking of this oil the same quantity which I did of the two petroleums just described, I obtained these results by its distillation:—

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Specific Gravity.
4 per cent. at .7202
17 " .740
19 " .768
12.5 " .802
6.25 " .821
6.25 " .8264
4 " .8287
4 " .829
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[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

Specific Gravity.
4 per cent. at .830
4 " .831
6 " .8319
87 —Oils distilled.
13 —Residue in retort—petroleum oil, pitch.

When the residual matters in retort were reduced to 27 per cent. of the charge they set at 60° Fah., and had a specific gravity of .856, owing to the large quantity of paraffin present. By mixing the first three distillates, and re-distilling them fractionally, I obtained 4 per cent. of an oil having a specific gravity of .7139. These results show that even a good sample of kerosene may be charged with paraffin and light oils to a very great extent.

The bulk of the oils, however, making up this kerosene are decidedly of low specific gravity, .832 being about that of the heaviest of them, so that it is seen the petroleum furnishing this kerosene (and I believe all our so-called American kerosenes) is of a different character from that of any yet found in this country. Thus our Poverty Bay petroleums are superior to these in being less charged with light oils, but perhaps a little inferior to them in having the bulk of their component oils of a heavier sort. However, I do not think much of this point, as the Canadian oil appears in good repute and is of precisely similar quality with the Waiapu oil.

Since the above results were obtained I have had a very small sample of an oil submitted to me by Mr. M'Leod, of precisely similar characters with the one furnished by Major Ropata. It is also from about the same locality. Mr. M'Leod describes the oil as having been skimmed from off the surface of the water which had oozed into a hole that had been sunk about 2 feet deep.

Mr. M'Leod affirms that there is a large tract of country about there from which oil can be obtained in this manner. It is therefore, I think, very likely that the oil may be found in quantity when properly worked for. Anyhow, the matter is well worth following up, and I feel anxious that the company now being formed to practically test our eastern districts in this matter may meet with the success it deserves.