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It is evident that none of the formates tested, in dosages greater than those necessary to kill all weevils, had an adverse effect upon the germination of wheat. Table IV-Fumigation Tests in a 500-Cubic Foot Vault w i t h Mixtures of Alkyl Formate and Carbon Tetrachloridea (Length of exposure, 24 hours) LARVAE KLLLED AnTineola AttaFUMIGANT MIXTURE threnus biselli- genus CClr DOSAGET E M P . vorax ella piceus Formate Lbs. per M . Volumes Volumes cu. ft. F. Per cent Per cent Per cent 10 76 8.5 70 3 (n-propyl) IIb 100 100 100 1 (isopropyl) 13 60 86 100 14 100 100 100 2 (sec-butyl) 7 92 90 86 8 100 100 100 2 (isobutyl) 8 96 90 100 9 100 100 100 2 (isoamyl) 7 100 100 100 a In all tests 20 specimens of clothes moths and 50 specimens of each of other species were used. b Italic figures indicate dosage for perfect kill.
Large-Scale Tests
Tests with these alkyl formates which can be made free from fire hazard by admixture with carbon tetrachloride were conducted on a larger scale in a commercial-type fumigation vault of 500 cubic feet capacity. The fumigant was
T’ol. 20. No. 4
poured through a trap door in the top of the vault into a shallow pan or trough suspended near the ceiling. The vault was then closed tightly for 24 hours. The insects used in the tests were the larvae of the clothes moth, Tineola biselliella, the black carpet beetle, Attagenus piceus, and the furniture beetle, Anthrenus voraz, species all highly resistant to fumigation. The larvae were placed in cotton-stoppered vials and buried in pieces of overstuffed furniture. Table IV shows the results of these tests. Additional tests indicate that the effectiveness of this group of fumigants decreases with the decrease in temperature and that to obtain perfect results the temperature should be at least 75’ F. Summary The vapors of methyl, ethyl, n-propyl, isopropyl, nbutyl, sec-butyl, isobutyl, isoamyl, and allyl formates are toxic to insects infesting stored products, such as rice weevils, clothes moths, carpet beetles, and furniture beetles. All these formates, except the methyl and ethyl formates, can be made free from fire hazard by the addition of carbon tetrachloride to the extent of 60 to 75 per cent by volume of the mixture, and some of these mixtures appear promising as economical fumigants for use in fumigating vaults.
A Simplified Manometer for Vacuum Distillations’ G. B. Heisig SCHOOL OF CHEMISTRY, UNIVERSITY OF M I N N E S O T A , h1INNEAPOLIS.
NYOKE who has run vacuum distillations using the regulation “S” type of manometer knows what a tedious job it is to clean and refill it if by chance his distillate has contaminated the mercury in the manometer. To minimize this difficulty the writer uses a somewhat different type of manometer whose construction is apparent from the accompanying sketch. It is made of Pyrex glass tubing. To fill the manometer, a layer of mercury about 7 mm. deep is poured into the reservoir. The manometer is then connected to the suction line and the vacuum is broken when the pressure reaches a minimum. This can be determined by the noise of the water pump. As the pressure increases the mercury will rise nearly to the top of the column. The manometer is then inverted and again attached to the pump. When the pressure has been reduced, the column of mercury is heated until the mercury boils. At the same time the tube should be tapped with a stick to help the air bubbles to rise. When the air has been boiled out, the heating is stopped, the manometer is placed in its usual position, and the pump is disconnected. The cleaning of the apparatus with cleaning mixture, the drying with alcohol and then ether, and the filling and boiling of the mercury require about an hour. When filled, the manometer is mounted on a wooden stand. Besides being easy to fill, the manometer has other advantages. Owing to the capillary constriction there is no danger of the mercury striking the top of the tube with sufficient force to break it. Even when a system is a t a pressure of 2 or 3 mm. the mercury rises gently to the top of the tube when the vacuum is broken. The reading of the column is facilitated by the fact that it is read directly, not by the difference of the height of mercury in two columns as in the “5”type of manometer. A millimeter scale made from a celluloid ruler or coordinate
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1
Received February 6, 1928.
MI“.
paper is attached beside the column of mercury, and is adjusted by comparing the manometer at different pressures with a standard manometer. If a standard manometer is not available, nearly as accurate results may be obtained by putting the zero of the scale on a level with the surface of
li II I
A Simplified Manometer
the mercury in the reservoir. Since the mercury from the tube spreads over the large pool as the pressure decreases, the height of the mercury in the pool increases only about 0.5 mm. even when the entire tube is emptied into it. The maximum error in reading, which would take place a t very low pressures, would be 0.5 mm. For ordinary vacuum
April, 1928
INDUSTRIAL AND ENGINEERING CHEMISTRY
distillations this difference is negligible. If any distillate enters the manometer it will enter the large chamber, and will not interfere with the reading of the column. No stopcock is necessary in connecting the manometer to a system. It can be connected directly by attaching a rubber hose to the tapered tube, which is bent a t a right angle. The absence of a stopcock makes the manometer
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very inexpensive. Including the labor of construction and the price of the glass tubing and mercury, the cost of the apparatus does not exceed $2.00. For this reason it is possible to use it in classes of general organic chemistry as well as by research workers in industrial and educational institutions. The glass blowing was done by E. F. Grienke of this university.
Solubility of Paraffin W a x in Pure Hydrocarbons' Paul Weber and H. L. Dunlap SCHOOL
OF
MINESA N D METALLURGY, ROLLA,M O .
ERY few data are available in the literature on the solubility of solid paraffins in the liquid hydrocarbons of lower molecular weight. Sakhanov and Vasil'ev2 determined the solubility of solid paraffins and the solidifying temperatures of materials containing them. The solvents used were liquid paraffins, benzene, machine oil, and acetic acid. They found that the solubilities increased rather rapidly with rise of temperature. For any particular solvent the solubility is greater the lower the melting point of the paraffin, and for any paraffin the solubility decreases wit'h the increasing density of the solvent. Sakhanov3 determined the solubilit'y of paraffin in various gasolines, kerosene, solar oil, paraffin oil, fuel oil, benzene, alcohol, and acetic acid. Sullivan, McGill, and French4 determined the solubility of closely fractionated paraffin wax of various petroleum fract'ions. The following conclusions were drawn from this work:
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1-The solubility of paraffin waxes increases as the melting point of the wax decreases. 2-The solubility of paraffin waxes in petroleum oil decreases with increasing viscosity of solvent. 3-Differences in solubility due to differences in the melting point of the wax, or to variations in the viscosity of the solvent, decrease with decreasing temperature.
The present authors determined the solubility of a fairly pure paraffin in the pure lower molecular-weight hydrocarbons in order to find out if any relationship existed between the decreasing solubility and the increased molecular weight of the solvent hydrocarbon. Preparation and Purification of Solid and Liquid Alkanes
SOLID PARAFFIX-The solid hydrocarbon was obtained from a sample of refined paraffin by careful recrystallization three times from benzene, the sample used being about 25 per cent of the original amount. That part which first crystallized from the benzene was taken for the next recrystallization each time. The last traces of benzene were removed by distillation under reduced pressure with a fine stream of air bubbling through the molten paraffin. This product undoubtedly contains several constituents, but as no purer products could be obtained, it was used for the comparative figures. The melting point of the paraffin was 56" C., and the density 0.775 a t 20"/4" C. LIQUIDHYDROCARBOKS-The liquid hydrocarbons were n-pent,ane, n-hexane, n-heptane, n-octane, and isodecane. The pentane was secured by a careful fractionation of natural gasoline. The heptane was obtained from the Eastman 1
2
*
4
Received November 4, 1927. X e f f y a n o e Khozyaisfuo, 6, 820 (1924). Petroleum, Z.,21, 735 (1926). Ind. Eng. Cliem., 19, 1042 (1927).
Kodak Company and refractioned. The others were prepared from alcohols using methods for synthesis suggested by the Eastman Kodak Company-namely, the Wiirtz reaction. These hydrocarbons, after treatment with cold sulfuric acid, washing with sodium carbonate solution, drying over metallic sodium and the final distillation, gave the constants indicated in Table I as compared with those given in the International Critical Tables. Table I-Constants of Liquid Hydrocarbons BOILING POINT SPECIFIC GRAVITY Found I. C. T. (2Oo/4O C.) 0 c. OC. Found I.C.T. 36.1-36.3 36.2 0.631 +Pentane 0.631 68.9-69.2 n-Hexane 69.0 0.661 0.660 98.2-98.4 98.4 0.684 0.684 n-Heptane 124.5-124.6 124.6 n-Octane 0.706" 0.707" Isodecane 159.8-160.1 160.0 0.721 0.722 Temperature 15'/4' C. HYDROCARBON
a
Solubility Determinations
APPARATUS-Ade Khotinsky thermostat with which temperature could be regulated to one-tenth of a degree was used for the bath. By using a strong salt solution and placing the thermostat in a cold room, the lower temperatures were easily maintained. Receptacles for the solutions consisted of ground-glass-stoppered wash bottles to which condensers had been sealede6 These flasks, with their condensers, were attached to a frame, which was rotated almost a quarter turn in the bath by an arm attached to a motor-driven wheel. PROCEDURE-ApprOXimately 200 cc. of solvent were placed in the flask and then solid paraffin was added until a slight excess remained undissolved at the temperature at which the solubility was to be determined. At least 5 hours were allowed for equilibrium to be reached before the first sample was taken. The flasks were then raised out of the bath, warmed to dissolve some of the excess paraffin, replaced in the thermostat, and the second sample taken after a minimum of 5 hours. All determinations were discarded that did not check within 0.1 per cent. The samples were placed in 50-cc. glass-stoppered weighing bottles to eliminate loss of solvent by evaporation before weighing. The solvents were then evaporated in a closed vessel (reduced pressure for isodecane) until the paraffin residue gave a constant weight. This method was used for each of the solvents with known weights of paraffin, and the exact procedures in which the paraffin could be recovered were used for the unknown samples. The melting points of the paraffin residues checked the original melting points within 1" C. EXPERIMENTAL DATA-The solubility of the solid paraffi in the liquid hydrocarbons is calculated and recorded as 5
Weber and Dunlap, Ind. Eng. Chem., 19, 481 (1927).
