INDUSTRIAL A,VD ENGINEERING CHEMISTRY
August, 1928
showed an average mortality of 79.5 per cent for kerosene alone and 92.4 per cent for kerosene containing 0.01 per cent of free nicotine. Other experiments with more viscous oils gave similar toxicities until the viscosity reached 100 to 110 seconds Saybolt, when the toxicity began to drop. This shows nicotine to be a more important factor in toxicity than oil and that the oil may be varied within wide limits as desired, or, in other words, the oil acted as a carrier for the active chemical, nicotine. T a b l e I-Distribution OIL USED
of N i c o t i n e in Oil and W a t e r M i x t u r e s a VISCOSITY AT TOTAL NICOTINE I N 100' F. (38' C . ) b Oil layer Water layer Seconds Per cent Per cent
Commercial ... 56 44 345 54 46 Kerosene Lubricating oil, very light 50 t o 60 48 52 75 t o 80 44 56 Lubricating oil, light 100 t o 110 42 58 Lubricating oil, light a Equal volumes of oil, containing 1 per cent of nicotine, and water were shaken together a t room temperature for 5 minutes, a n d t h e amount of nicotine determined in each layer. b T'iscosity of kerosene determined b y Saybolt thermoviscometer; t h a t of lubricating oils determined b y Saybolt Universal viscometer.
Applications of Principle The establishment of this principle of the use of oil for its physical properties, as being equal to or superior to its insecticidal value, makes possible the use of the more volatile and cheaper oil fractions than when dependence is placed alone on the oil for toxicity. Volatile oils are safer to use on foilage, other factors being uniform, than those which persist in the leaf for long periods of time. The general trend in California field practice is toward the use of light fractions having a viscosity of 70 to 80 seconds rather than 100 seconds or more. Much remains to be worked out in choosing the exact type of oil and the most sat'isfactory combining chemicals, but the progress made indicates a wide range of usefulness in the combinations of oil and active insecticides, fungicides, and herbicides. The most common application of the principle of oil as a carrier and also solvent for some other active insecticide
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is that of pyrethrum extract, the basis for many commercial fly sprays. Para-dichlorobenzene is another standard insecticide readily soluble in oil which is useful for some purposes. There are also reports of increased efficiency from lime-sulfur sprays when combined with compatible emulsions. Such reports can well be credited when the increased penetration of such a combination is known. Effect on Plant The use of oil on foliage, either alone or in combination, must always be studied with reference to compatibility with the plant. Acute injury is seldom seen with the type of oils now commonly used, but there is still grave danger of interference with normal functions, including the inhibition of starch formation, from the presence of oil in the cell structure, and disturbances of the transpiration rate. Dormant spraying of the tree is now sufficiently understood so that the blooming date may be either retarded or stimulated, as desired, with a fair degree of certainty. Prune trees in central California sprayed the latter part of Sovember nearly always show a retardation of blooming dates amounting to 5 to 7 days. Oils applied in December, during the period of the nearest approach to dormancy, cause but little change in blooming time, but spraying during January gives an early bloom while later applications retard the bloom. It is now a debated question whether it is not possible to secure a continued uniform increase in the set of fruit year after year without too great B drain on the vitality oi' the trees. Still mother beneficial physiological reaction of oil sprays has been noted in southern Califorilia-viz., the reduction of injury on lemons and oranges from desiccating winds. Some of the values now attributed to oil applications may be discredited later, but a t least this field should not be overlooked. It is hoped also that the plant physiologist and horticulturist will assist the entomologist and chemist in determining the true value of mineral oil in our diversified problems of horticulture.
McBain-Bakr Balance for Sorption of Vapors Film Materials"'
Fibrous and
P. T. Newsome EASTMAN KODAK COMPANY, ROCHESTER, pi. Y.
HE McBain-Bakr3 quartz fiber spring balance has been found very useful for measuring the sorption of vapors by fibrous and film materials such as cellulose and cellulose esters. T h e a p p a r a t u s shown in the figure is placed inside a carefully controlled air thermostat. Samples of the material are suspended from the calibrated spring a n d e v a c u a t e d through D by means of an oil pump to constant weight a t a pressure of
