LIBKAKT STATE PLANT BOARD E-511 September I9U0 United States Department of Agriculture Bureau of Entomology and Plant Quarantine STANDARD METHOD FOR THE DISTILLATION OF GERANIOL 3y Louis Koblitsky and R. D. Chisholm, Division of Insecticide Investigations Introduction Commercial geraniol is the major constituent of the "bait used in traps for the Japanese "beetle (Popillia japonica Newman) . The specif ica- t ion si/ under which it is purchased include the statement, "not more than 5 percent boiling under 225° C. or more than 18 percent boiling over 2^5° (760 mm. pressure)." Manufacturers of geraniol employ a diversity of methods and apparatus for the determination of the boiling range, and all of these differ from those used in the laboratory of this Division at Moorestown, N. J. As the results obtained are influenced markodly by the form of apparatus, rapidity of distillation, and barometric pressure, as well as other factors,- it is desirable that a standard method be adopted. This paper is a study of some of these factors and describes the apparatus and methods now in use at this laboratory for the determination of the distillation range of geraniol to be used for Japanese beetle bait. Various authorities^' > U » z/ agree that an ordinary distilling flask is satisfactory for the determination of the boiling range. Gildemeister and Hoffman-' and the Pharmacopoeia^/ state that the entire mercury column of the thermometer may be surrounded by the vapors of the distilling oil, but the former suggest that the thermomoter bo adjusted so that the top of \' Metzger, F. W. , and Maines, W. W. Relation between the physical properties and chemical components of various grades of geraniol and their attractiveness to the Japanese beetle. U. S. Dept. Agr. Tech. Bui. 501, lU pp., illus. 1935. 2/ Gildemeister, E. , and Hoffman, F. The volatile oils. Second edition by E. Gildemeister, Vol. 1, 677 pp. 1919. London. y Parry, E. J. The chemistry of essential oils and artificial per- fumes. Ed. 3, Vol. 2, 3>+h pp. 1919. London. —' United States Pharmacopoeial Convention. Pharmacopoeia of the United States of America. Eleventh Revision. 1936. STA.TE «&*»■• the column of mercury is slightly above the outlet tube, while directs that the thermometer he adjusted so that the top of th . ,«,j. with the center of the opening of the outlet tube. Tho Pharmacopoeia also specifies that a condenser with a water jacket ko to 60 cm. in length he used and that the distillation he conducted so that k to 5 ml. are distilled per minute. The standard suggested in this circular. takes into account (l) the length of the condenser, (2) the type of distillation flask, (3) the type of thermometer and the location of the "bulb during distillation, (U) the rate of distillation, and (5) the effect of barometric pressure. An attempt was also made to use standard apparatus readily obtainable in the open market. In comparing the results obtained on distillation of a commercial geraniol in the apparatus selected with those obtained in other distilling apparatus, it was found that J. (l) The greater the length of the condenser, the higher is the observed boiling point. (2) The type of distilling flask (Engler or Ladenburg) was of little importance. (3) The closer the ther- mometer is to the level of the liquid, the higher is the observed boiling point. The Anschutz type thermometer, since it is completely within the nock of the distillation flask, eliminates the need for the application of a stem correction, (k) The observed boiling point varies directly with the rate of distillation. On this basis, the definite rate of distillation of not less than 3 or more than U ml. per minute is specified in the pro- cedure* (5) A change in the barometric pressure of 20 mm. causes a change in the boiling point of 1° C. The effect of barometric pressure was deter- mined from a series of distillations made at different pressures, several methods being used. Apparatus Flask. — Engler distilling, 100 ml. capacity, with the vapor tube 9 cm. above the surface of the liquid when tho flask contains 100 ml., and with a neck 18.5 cm. in length. This flask conforms with tho 1935 A. S. T. M. permanent standards, serial designation D 86 - 35, with the single exception that the neck of the flask is IS. 5 cm. in length instead of 15 cm. Condenser. — Tho condenser consists of a s/lS inch 0 D seamless brass tube 22 inches long, located at ah angle of 75° from vortical in a cooling bath of ice and water 15 inches long. This condenser conforms with the 1935 A.' S. T. M. permanent standards, serial designation D 86 - 35* Electric heater. — The oloctric heater is of such capacity (550 watts is sufficient) as to pormit the first drop to fall from the condenser in not less than 8 or more than 10 minutes. It is fitted with a continuously adjustable rheostat and a refractory top U-3A inches square with a 1-1/2 inch round hole. Shield. — The shield is made of 22-gauge metal, asbestos lined. It fits snugly over and extends 11 inches above and 3 A inch below the top of the heater. It is U-3/U inches square at the top end and 5-1/2 inches square at the bottom end. It is fitted with an asbestos-lined, tight-fitting cover - 3 - and a window, 7 inches long and 3 inches wide, of heat-resisti located 1 inch from the top and centered in the face. A slot tube, 6 inches long and 1/2. inch wide, extends upward from the bottom on a side adjacont to the window. Thermometer. — The thermometer is of the Anschutz type with a National Bureau of Standards report. It has a range of from 200° to 270° C, sub- divided in l/2° intervals. It is approximately 130 mm. long and 6 mm. in diameter. Receiving cylinder. — The receiving cylinder is a so-called normal or precision cylinder of 50 ml. capacity, having an internal diameter of 2 cm., and is graduated at intervals of 0.5 ml. The assembled apparatus is shown in figures 1 and 2. Procedure (1) The condenser hath is filled with cracked ice, and enough water is added to cover the condenser tube. The temperature is maintained between 0° and 5° C. (2) The condenser tube is swabbed to remove any liquid remaining from the previous tost. A piece of soft cloth attached to a cord or copper wire is used for this purpose. (3) Fifty ml. of the geraniol is transferred to the Engler flask by means of a pipette calibrated to deliver 50 ml. of geraniol at 25° C. The flask contains sevoral small pieces of pumice or a few glass beads. (U) The charged flask is placed in the l-l/2 inch opening in the refractory top of the electric heater, and the vapor outlet tube is inserted in the condenser tube. A tight connection is made by means of a cork through which the vapor tube passes. The position of the flask is so adjusted that the vapor tube extends into the condenser tube not less than 1 inch or more than 2 inches. A soft plug of absorbent cotton is inserted about l/2 inch into the neck of the distilling flask, (5) The covered shield is placed so that it will be supported by the top of the heater. (6) The receiving cylinder is placed at the outlet of the condenser tube in such a position that the condenser tube extends into the receiving cylinder at least 1 inch but not below the 50 ml. mark. (7) When everything is in readiness, heat is applied at a uniform rate and so rogulated that the first drop of condensate falls from the con- denser in not less than 8 minutes or more than 10 minutes. As soon as the geraniol vapor's start to rise in the neck of the distilling flask the cotton plug is withdrawn and the condensed water removed from the inside of the neck of the flask with filter paper. The thermometer provided with a cork is then fitted tightly into the flask so that it is in the middle of the nock stateVl^nt boabd and so that the lower end of the capillary tube is on a level • of the "bottom of the vapor outlet tuhe at its junction with th flask, and the cover of the shield is replaced. After the first drop falls from the end of the condenser the receiv- ing cylinder is moved so that the end of the^ condenser tube touches the side of the cylinder. The heat is then so regulated that the distillation pro- ceeds at a uniform rate of not less than 3 or more than U ml. per- minute. The temperatures are observed when the volume- of the distillate is 2.5 ral» (5 percent) and kl ml, (82 percent). The distillation is stopped at this point to avoid the formation of a charred residue in the flask. The observed temperatures are corrected to 7^0 mm. at 25° C "by sub- tracting 1° from the observed temperature for each 20 mm. above 760 mm. and adding 1° for each 20 mm. below 7&0 mm. Accuracy of Results With proper care and attention to detail, duplicate results obtained for the temperature at which 2.5 ml. (5 percent) is distilled should not differ from each other by more than 0.5°, while those for the temperature at which kl ml, (82 percent) is distilled should not differ from each other by more than 1°. T -SO Figure 1. — Standard distillation apparatus without shield, r\ Figure 2. — Standard distillation apparatus, with shield in position, UNIVERSITY OF FLORIDA IIMIIIMIIIIIII 3 1262 09224 7476