US 2325421 A
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for medicinal purposes. the usual physical and chemical tests of various Patented July 27, 1943 IDENTIFICATION OF WHITE MINERAL OIL Allen L. Omohundro, Wilton, and Emil C. Fanto,
Fairfield, Conn., assignors to McKesson & Robbins, Incorporated, Bridgeport, Conn., a corporation of Maryland Application Aprill, 1942, Serial No. 437,114
- 2 Claims.
This invention relates to the identification of white mineral oils of the type commonly used It has been found that oils of this type are inefiective for the purpose of identification, since While mineral oils manufactured with the greatest care show substantially the same specific gravity, viscosity, presence of unsaturates, Saybold color and the like, as oils which are manufactured with much less care. The result has been that the cheaper grades of white mineral oils have been extensively substituted for the better grades put out by reputable manufacturers, due to the fact that it has been impracticable to prove such substitution. This application is a continuation-inpart of my prior application Serial No. 202,836, filed April 19, 1938, for Mineral oils used for medicinal purposes.
The general purpose of this invention is to provide a method and means for thev identification of white mineral oil which will enable a manufacturer to distinguish his oil from other white mineral oils having substantially the same.
chemical and physical characteristics. A further purpose is to provide a type of identification which cannot readily bewdetected either by observation or by the tests available to the average merchant handling the oil. These objects are in general attained by dissolving in the oil minute proportions of a substance whose presence can be readily and positively determined by spectrophotometry. In order to besatisfactory the substance must be one which does not afiect the appearance, odor or flavor of the oil, as any change in these characteristics would reveal its presence. Moreover, since the oil is generally intended for internal use, the identifying substance must not affect either the palatabilityoi the oilor its effect on the user. The substance must also be capable of producing a characteristic and readily identified change in the light absorption curve as determined by standard spectrophoto metric methods.
These objects are attained by the use of carotene as the identifying substance. It is readily obtained, dissolves in white mineral oil without producing any color when used'in proportions ible spectrum which reaches a maximum in the neighborhood of 450 millimicron s, even' when present in infinitesimal proportions, being capable of definite spectrophotometric identification when present in proportions as low as one part of carotene to one hundred million parts of oil. Furthermore, th characteristic change in. the light absorption curve varies in degree with the use of diiierent proportions of carotene.
The carotene has no adverse effect on the white mineral oil, and in fact is beneficial to a certain extent, since it acts as a deoxidant. It therefore may be used for identification purposes in proportion as high as may be found practical with any particular type Or color of oil Without losing the desirable characteristics that have been set forth. It has been found that when treating standard white mineral oil, proportions of carotene as high as one part in twenty-five million parts of oil are practicable.
The distinctive effect of carotene on the light transmission curve of the oil occur in the visible spectrum, a fact which is advantageous since it facilitates identification. It has been found however that when white mineral oil containing carotene is exposed to light it develops an additional deviation in the light transmission curve in the ultra-violet range, which may be used as a further basis for identification as well as for determination of the exposure of the oil to light. This deviation is produced only upon exposure of the treated oil to light for a substantial period. One sample exposed to indirect light for ten months under conditions similar to-those normally encountered on a retailers shelf showed a substantial ultra-violet deviation, though apparently such deviation had not reached its limit.
The amount of deviation produced in a given pedation, the absorption of light in the ultra-violet spectrum being affected by a product of such change. The change likewise tends .to reduce somewhat the deviation in the visible spectrum characteristic of the presence of carotene, but not to an extent which affects materially 'the ability to identify the oil-in this manner.
The light absorption efiect of carotene appears I clearly in spectrophotometric curves representing the light absorption factor at various wave lengths. Curves of this type are shown in the drawing, which represents tests of white-mineral oil by ordinary spectrophotometric methods.
In the drawing Fig. 1 is a graph showing the light absorption factor in the visible wave length range between 400 and 600 millimicrons, obtained by testing white mineral oil containing one part of carotene to fifty million parts of oil;
Fig. 2 is a similar graph obtained by testing the same oil containing no carotene;
Fig. 3 is a spectrophotometric graph showing the light absorption factor in the ultra-violet wave length range between 270 and 370 millimicrons, obtained by testing white mineral oil containing one part of carotene in fiity million parts of oil which has been exposed to-light for a substantial period; and
Fig. 4 is a similar graph resulting from a test of the same carotene-containingoil that has not been exposed to light for a substantial period.
It will be apparent from a comparison of the curves in Figs. 1 and 2 that white mineral oil containing extremely small proportions of carotene can be immediately and positively identified by spectrophotometry. When carotene is used in the proportion indicated the additional light absorption in the region of 450 millimicrons is about five per cent; and the resulting depression in the light absorption curve in this particular part of the spectrum is believed to be peculiar to carotene. The maximum absorption effect occurs between 447 and 452 millimicrons, though it extends for a substantial distance on either side of this range,
ordinarily being apparent between about 400 and about 520 millimicrons.
Comparison of the curves in Figs. 3 and 4, based on measurements at prominent lines of the mercuryspectrum, provides an additional basis for identification if the oil has been exposed to light, and serves further as a means for determining the effect of such exposure. The principal deviation in the ultra-violet range occurs in the region between 290 and 330 millimicrons. It has been found that with different types of oil the prin-- cipal deviation occurs at different points in or carotene is suitable as it is readily soluble in the oil, and normally consists of about ten per cent alpha carotene and ninety per cent beta carotene. These proportions however are not critical, and may be varied without afi'ecting the usefulness of the carotene as an identification medium. The
term carotene as used herein is intended to include either form of carotene or both forms in combination in any proportion.
In order to bring out adequately the deviation caused by the carotene an oil sample of substantial diameter. should be tested, the tests illustrated having been made on a sample contained in a'five centimeter cell.
It should be noted that the proportion of carotene employed is very much less than that which is required for identification by fluorescence, the amount of carotene necessary for identification by the latter method being such that the oil would be highly colored. The use of carotene for oil identification is likewise free from the principal objection to other methods proposed for identification, which comprise the addition of substances whose presence may be determined by titration or other simple and well known chemical tests, since such tests are readily carried out by druggists and other merchants who handle this type of oil.
We have described what we believe to be the best embodiments of our invention. We do not wish, however, to be confined to the embodiments shown, but what we desire to cover by Letters Patent is set forth in the appended claims:
1. An oil composition adapted to be used internally and to be identified by absorption of light in the visible spectrum, the composition consisting essentially of white mineral oil with a minor proportion of beta carotcnedispersed in the oil, the beta carotene being present in proportion not substantially in excess of about 1 part to 25,000,000 parts of the oil, having a distinctive light absorption efiect in the visible spectrum, and being converted by exposure of the composition to light to a product having a different light absorption efiect, thus providing a confirmatory means for identification of the composition spectrophotometrically.
2. A composition as described in claim 1, the proportion of beta carotene being about 1 part to approximately 25,000,000 to 100,000,000 parts of the white mineral oil.
ALLEN L. OMOHUNDRO. EMlL C. FANTO.