ORIGIN OF PETROLEUM.

Taranaki Central Press, Volume IV, Issue 344, 27 January 1937, Page 3

ORIGIN OF PETROLEUM.

CONFLICT OF VIEWS, fcl SIMILARITY TO COAL. LIKELIEST THEORY. Everyone is familiar with the idea that common coal is produced by Hie steady decomposition, over long geological periods, of the vegetable matter which has accumulated in certain strata ot the earth’s crust (writes a scientific correspondent in the Melbourne Age). . Practically every gradation of the process is known, the intermediate products, peat and lignite, being quite plentiful; while the change has actually been reproduced on a limited scale in the laboratory. But with petroleum the matter is by no means so clear cut. The oil Is found under such widely-varying conditions and the composition itself varies in Such a peculiar manner from place to-place that-no one as yet has been able to point with conviction to any particular parent substauea as the sole source of all the present-day deposits.

As we -shall se«, it is quite likely that more than one explanation is correct, since the saturated paraffins that constitute Pennsylvania petroleum may have a different origin from the cyclic paraffins which are the basis of Caucasian oil; while the mixed oils of Galicia may'have a mixed origin, or be the offspring of a different parent altogether. Inorganic Theory. As certain deposits of oil are found in the‘’most ancient Silurian rocks, it is difficult ter imagine a sufficient accumulation of vegetable or animal ma.tter.t9_account for their .origin. Accordingly, the famous Russian Mendeleeff, suggested that the oil was formed in the earth quite independently of the existence of living things, . either vegetable or | animal. This theory, called the inorganic theory of assumes that various heavy metals, such as iron and manganese, have combined with carbon in the Interior of the earth to form metallic carbides. These have come in contact with water or steam and may have decomposed to form hydrocarbons, which differ in structure according to the conditions of temperature and pressure. A homely analogy is the production of the hydrocarbon, acetylene, by the action of water on calcium carbide, ah action Used all over the world in the acetylene lamp. -

The French scientist Sabatier extended the inorganic idea by showing that if free', meta (si a tso .existed in the depths -of the -earth some of them, such as sodium, would generate hydrogen when -they came -1n "contact with water, while others, such as nickel, would act- a?; catalysts, and facilitale Ifre combination of hydrogen with acetylene and other hydrocarbons, thus producing mixtures comparable with natural oils. Important Features. Nevertheless, Ifie inorganic thoery is not generally considered a very happy one. Scientifically It" takes too much for granted. Quite apart from this, it fails completely to account for two. features associated with natural oils, which indirectly are of considerable import. In the first place, certain varieties of jpetroleum.,are optically active—-that is, they have the power of rotating a beam of polarised light; and, in the second place, they nearly all contain an appreciable quantity of nitrogen in the form of nitrogenous bases. From some points of view these two facts are scarcely worth attention, but from the point of view of origin they are all-important, since they both point unmistakably to an organic or living source.

Wide , experience has shown that optically active substances are nevez produced by purely inorganic means, but are always the result of animal o? vegetable. life processes, while complex nitrogenous bases, although thej may be produced in the laboratory bj circuitous means, are, in nature, inseparably associated with the life principle. When we add to this the fact that sulphur, in the form of organic sulphide, is frequently found in petroleum oil. we seem forced to the conclusion that somewhere in their past history these oils have had direct connection with organic processes. 'As a result, two organic theories of origin have been put forward. One suggests .that oil, like coal, came originally from vegetable matter, while the other suggests that the original source’ is to be found in the cumulative effect of decaying micro-organ-isms. each contributing a minute amount to the ultimate huge bulk.

Varying Properties. The (Ifeory of vegetable 'origin, I giving, as it does, a common parentage j o coal and oil, would seem to demand : hat these two substances must possess some features of resemblance. Actu- ! ally {hey show widely-varying chemi■al properties, but the fact that coal is converted into oil by the modern | hydrogenation process is 'sufficient tc i indicate certain similarities. Briggs. I of. Edinburgh, a staunch supporter of the vegetable theory, has plotted the >xygen-carbpn content of individual joais and oils, and has used the development graphs to deduce that there is no essential difference between the material which was the origin of coal and that which was Ihe origin of oil. The second of these theories, the micro-organic theory, assumes that oil results from the steady accumulation of decaying microscopic plant and animal life. At first sight this may appear a little far-fetched, but scientifically this theory is the most convincing of them ajl. The New South Wales kei-osene shale deposits, for example, are found to consist almost exclusively of the compound colonies of a single alg/t, Reinschia australis, the cell walls of which are lined with a wax-like deposit. Examination of the Tasmanian oil shales reveals that they, too, lend direct support to the micro-organic theory. To a lesser extent the same holds for the Lakes Entrance oi] seepages. In fact, we have here a fairly definite relation between oilbearing materials and an organic source of origin.

But perhaps th • most interesting information comes from the Coorong district of South Australia. Here a greenish-grey scum forms on the surface of the water, which dries by evaporation to a brownish, elastic material known as Coorongite. Thiessen, of America, has shown that Coorongite consists mainly of unicellular algae cemented into waxy colonies, so nearly like Reinschia of the oil shales of New South Wales as to leave little 1 doubt of a common origin. It yields petroleum-like oils on distillation. The local suggestion that it indicates some hidden source of petroleum oil is entirely unwarranted; on the contrary, it seems to be a beautiful example of oil in its early stages. Making allowance for the steady accumulation over long geological periods, little imagination is required to build up from such intermediate products the large oil deposits scattered over the, surface of the earth.