THE STANDARDISATION OF PETROLEUM AND TAR OILS AND PREPARATIONS AS INSECTICIDES1
Authors: MARTIN HUBERT 
Published: February 2008

SUMMARY.

Preparations of certain hydrocarbon oils of either tar or petroleum origin have found wide use in horticulture as insecticides, the oil functioning as an ovicide, an acaricide or a scalecide. Critical experiment supplemented by general experience has shown that the suitability of the oils for these purposes is determined by certain physical and chemical criteria which, collectively, constitute a specification. Previous work on the subject is reviewed and a series of specifications is suggested.
Because of the several pnrposes for which tar and petroleum oils are used, a minimum of five grades of the oils themselves, two of tar and three of petroleum oils, is necessary to cover all requirements.
Tar oils suitable for the preparation of spray fluids are covered by Grades A and B, which are defined as follows:

Grade A. The oil should contain not less than 88 per cent. by weight of neutral oils, not more than 5 per cent. by weight of solid matter, and should be free from alkali, as determined by the prescribed methods of analysis. The neutral oil isolated by the prescribed method should have a specific gravity of 1.09–1.11 (604dG F.), should be completely soluble in dimethyl sulphate and should be of boiling range such that at least 90 per cent. by volume distils above 270d̀ C., at least 50 per cent. above 325d̀ C. and at least 20 per cent. above 365d̀ C.An oil fulfilling these requirements will be suitable for the preparation of winter washes intended for general purposes. Grade B. The oil should contain not less than 75 per cent. by weight of neutral oils, not more than 5 per cent. by weight of solid matter and should be free from alkali. The neutral oils, isolated by the prescribed method, should have a specific gravity of between 1.05 and 1.11 at 60d̀ F., should be completely soluble in dimethyl sulphate, and should be of boiling range such that at least 90 per cent. by volume distils above 230d̀ C., at least 50 per cent. above 290d̀ C. and at least 20 per cent. by volume above 335d̀ C.An oil satisfying this specification will be suitable for the preparation of washes intended for the control of aphid and psyllid eggs by application during the dormant season.

Petroleum oils, described as Grades E, F and G, should consist entirely of neutral oils, should be free from alkali, and should have a specific gravity of between 0.86 and 0.92 at 60d̀ F.

Grade E. The neutral oils should have a viscosity of between 125 and 500 sec. Redwood 1 at 70d̀ F., should have a boiling range such that not less than 90 per cent. by volume distils above 315d̀ C., at least 50 per cent. above 350d̀ C. and not less than 20 per cent. above 380d̀ C., and should have an unsulphonated residue of not less than 60 per cent. by volume, all figures being determined by the prescribed methods of analysis.An oil fulfilling these requirements will be suitable for the preparation of winter washes or of washes intended for application at certain periods intermediate between bud burst and blossoming on varieties of fruit tolerant to petroleum oils less highly refined than Grade F oils. Grade F. The neutral oils should have a viscosity of between 100 and 400 sec. Redwood 1 at 70d̀ F., should have a boiling range such that at least 90 per cent. by volume of the oils distils above 310d̀ C., at least 50 per cent. above 345d̀ C. and at least 20 per cent. above 375d̀ C., and should have an unsulphonated residue of not less than 80 per cent. by volume when determined by the prescribed methods.An oil satisfying the above requirements will be suitable for the preparation of washes intended for application at periods intermediate between bud burst and blossoming on varieties of fruit tolerant to petroleum oils less highly refined than Grade G oils. Grade G. The neutral oils should have a viscosity of between 75 and 150 sec. Redwi>od 1 at 70d̀ F., should be of boiling range such that at least 90 per cent. by volume distils above 300d̀ C., but not less than 10 per cent. by volume should distil below 330d̀ C., not less than 50 per cent. by volume should distil above 340d̀ C., and below 365d̀ C., not less than 20 per cent. by volume should distil below 370d̀ C., and not less than 80 per cent. by volume should distil below 390d̀ C., and the unsulphonated residue should not be less than 90 per cent. by volume, all figures being determined by the prescribed methods.An oil conforming to this specification will be suitable for the preparation of sprays intended for application to foliage of oil‐tolerant varieties of plant.

The successful use of oils of the above grades is dependent upon proper application in spray form, for which suitable methods of emulsification are necessary. Although methods are available whereby the grower can prepare emulsions of these oils, it is simpler for him to use manufactured oil preparations which merely require mixing with water to give the required spray. Such oil preparations are of two types, miscible oils (designated M.O.) and stock emulsions (S.E.). Miscible oils are clear oily liquids which, on mixture with water, yield emulsions. Stock emulsions are cream‐like pastes and, as their name implies, are concentrated emulsions. The amount of neutral oil which can conveniently be incorporated in the preparation is dependent on the type of emulsifier used, and, to cover all types, four types of preparations are specified. In addition, two further grades of neutral oil, Grades C and D, are necessary to cover combined tar‐petroleum oil preparations.
The following specifications for tar and petroleum oil preparations cover all present requirements:

Tar oil preparations. Grade A, Type M.O. The preparation should contain not less than 70 per cent. by weight neutral oils, not more than 4.2 per cent. by weight tar acids and not more than 5 per cent. by weight solid matter, as determined by the prescribed methods. Grade A, Type S.E. The preparation should contain not less than 60 per cent. by weight neutral oils and not more than 3.6 per cent. by weight tar acids, as determined by the prescribed methods.The neutral oil, isolated by the prescribed method from both the M.O. and S.E. types, should have a specific gravity of between 1.06 and 1.11 at 60d̀ F., the percentage insoluble in dimethyl sulphate should not exceed 10 per cent. by volume, and the boiling range of the oil should be such that at least 90 per cent. by volume distils above 270d̀ C., at least 50 per cent. by volume above 325d̀ C. and at least 20 per cent. by volume above 365d̀ C.Preparations conforming to the Grade A, Types M.O. and S.E. specifications will be suitable for application as tar oil winter washes for general purposes. Grade B, Type M.O. The preparation should contain at least 60 per cent. by weight neutral oils and not more than 9 per cent. by weight tar acids and not more than 5 per cent. by weight solid matter, as determined by the prescribed methods of analysis. Grade B, Type S.E. The preparation should contain at least 50 per cent. by weight neutral oils, and not more than 7.5 per cent. by weight tar acids, as determined by the prescribed methods.The neutral oils, isolated by the prescribed method from preparations conforming to the Grade B, Types M.O. and S.E. specifications, should have a specific gravity of between 1.05 and 1.11 at 60d̀ F., the percentage insoluble in dimethyl sulphate should not exceed 10 per cent. by volume and the boiling range should be such that at least 90 per cent. by volume distils above 230d̀ C., at least 50 per cent. by volume above 290d̀ C. and at least 20 per cent. by volume above 335d̀ C.Preparations conforming to the above Grade B specifications are suitable for application as tar oil winter washes intended for the control of aphids and psyllids. Tar‐petroleum oil preparations. Grade C, Type M.O. The preparation should contain not less than 74 per cent. by weight neutral oil and not more than 2 per cent. by weight tar acids and not more than 5 per cent. by weight solid matter, as determined by the prescribed methods of analysis. Grade C, Type S.E. The preparation should contain not less than 62 per cent. by weight neutral oils and not more than 1.5 per cent. by weight tar acids, as determined by the prescribed methods of analysis.The neutral oil, isolated by the prescribed method from Grade C preparations, should have a specific gravity not less than 0.99 at 60d̀ F., and should have a boiling range such that at least 90 per cent. by volume distils above 283d̀ C., not less than 50 per cent. above 335d̀ C. and not less than 20 per cent. above 375d̀ C. Not more than 53 per cent. by volume of the neutral oil should be insoluble in dimethyl sulphate and the unsulphonated residue should not be less than 32 per cent., all determinations being made by the prescribed methods.Preparations conforming to the Grade C, Types M.O. and S.E. specifications will be suitable for use as combined tar‐petroleum oil winter washes for general application on varieties of plants to which washes of high (e.g. 9 per cent.) oil concentration are injurious. Grade D, Type M.O. The preparation should yield not less than 75 per cent. by weight neutral oils, not more than 2 per cent. by weight tar acids, and not more than 5 per cent. by weight solid matter, when examined by the prescribed methods of analysis. Grade D, Type S.E. The preparation should contain not less than 63.5 per cent. by weight neutral oils and not more than 2 per cent. by weight tar acids, when determined by the prescribed methods of analysis.The neutral oil, isolated by the prescribed method from preparations of the Grade D, Types M.O. and S.E. specifications, should be of specific gravity not less than 0.95 at 60d̀ F., should be of boiling range such that not less than 90 per cent. by volume should distil above 290d̀ C., not less than 50 per cent. by volume should distil above 340d̀ C. and not less than 20 per cent. should distil above 375d̀ C., and not more than 70 per cent. by volume of the neutral oil should be insoluble in dimethyl sulphate and the unsulphonated residue should not be less than 42 per cent. by volume, all determinations being made by the prescribed methods.A preparation conforming to the requirements of the Grade D, Types M.O. arid S.E. specifications will yield a combined tar‐petroleum oil winter wash suitable for application for general purposes to varieties of plant tolerant to sprays of high oil content. Petroleum oil preparations. Grade E, Types M.O. and S.E. I. The preparations should contain not less than 80 per cent. by weight neutral oil, determined by the prescribed method of analysis. Grade E, Type S.E. IIa. The preparation should contain not less than 66.7 per cent. by weight neutral oil, determined by the prescribed method of analysis. Grade E, Type S.E. IIb. The preparation should contain not less than 66.7 per cent. by weight neutral oil and should contain no free ammonia or alkali salts yielding insoluble calcium salts or an ash containing free alkali, when tested by the prescribed methods of analysis.The neutral oil, isolated from preparations of the Grade E, Types M.O. and S.E. I, IIa and IIb specifications, by the prescribed method, should conform to the Grade E specification of petroleum oils given above (p. 407).Preparations conforming to the requirements of the Grade E specifications are suitable as petroleum oil sprays for dormant use and for application to foliage of varieties of plants tolerant to sprays containing semi‐refined petroleum oils. Preparations of the Grade E, Type S.E. IIb specification are suitable for combination with lead arsenate, lime sulphur or Bordeaux mixture on tolerant varieties of plants. Grade F, Types M.O. and S.E.I. The preparations should yield not less than 80 per cent. by weight neutral oil, determined by the prescribed method of analysis. Grade F, Type S.E. IIa. The preparation should contain not less than 66.7 per cent. by weight neutral oil, determined by the prescribed method of analysis. Grade F, Type S.E. IIb. The preparation should contain not less than 66.7 per cent. by weight neutral oils, should yield an ash containing no free alkali, and should contain no free ammonia, or alkali salts yielding insoluble calcium salts, as determined by the prescribed methods of analysis.The neutral oils, isolated by the prescribed method from preparations of the Grade F, Types M.O., S.E. I, and S.E. IIa and b, should conform to the specification for Grade F petroleum oils given above (p. 408).Preparations satisfying the requirements of the Grade F specifications are suitable as petroleum oil washes intended for application to the foliage of plants tolerant to half‐white petroleum oils. Preparations of the Grade F, Type S.E. IIb specification are suitable for use in combination with lead arsenate, lime sulphur or Bordeaux mixture upon foliage of varieties of plants tolerant to such combined washes. Grade G, Types M.O. and S.E.I. The preparations should contain not less than 80 per cent. by weight neutral oil, as determined by the prescribed method. Grade G, Type S.E. II a. The preparation should contain not less than 66.7 psr cent. by weight neutral oil, as determined by the prescribed method. Grade G, Type S.E. II b. The preparation should contain not less than 66.7 per cent. by weight neutral oil, and should contain no free ammonia or alkali salts yielding insoluble calcium salts or an ash containing free alkali wheri examined by the prescribed methods of analysis.The neutral oils, isolated from preparations of the Grade G specifications, should conform to the specification for Grade G petroleum oil given above (see p. 408).Preparations satisfying the requirements of the Grade G, Types M.O., S.E. I, IIa and b specifications are suitable as petroleum oil washes for application to the foliage of plants tolerant to petroleum oil sprays. Those of the Grade G, Type IIb specification are suitable for use in combination with lead arsenate, lime sulphur or Bordeaux mixture for application to the foliage of plants tolerant to such combined washes.For ease of reference and comparison the various specifications proposed are tabulated in the Schedule given above (see pp. 394–5).

Methods of analysis are suggested for the determination of the various criteria required by the specifications and evidence is given of the suitability of the suggested methods.
The application of the proposed specifications is illustrated by examples from oils and preparations which have been or are at present used in spray practice.