I N D U S T R I A L A N D ENGINEERING CHEMISTRY
March, 1924
ing points indicate that the compounds are isoheptane (2methylhexane) and normal heptane. The most accurate values of the constants of these compounds as isolated from petroleum by Young14were isoheptane, b. p. 89.9" to 90.4" C., specific gravity 0.7067 (0°/4" C.) or 0.6936 (15.5"/15.5O C.), (this value of the specific gravity was considered slightly high by Young); normal heptane, b. p. 98.25" to 98.45" C., specific gravity 0.70186 (0"/4" C.) or 0.6888 (15.5"/15.5" C.). Thorpe'sls pure isoheptane, synthetically prepared, had b. p. 90.3" C., specific gravity 0.69692 (0"/4O C.) or 0.6838 (15.5"/15.5' C.); and his pure normal heptane from Pinus sabiniana had b. p. 98.43' C., specific gravity 0.70048 (0"/4" C.) or 0 6867 (15.5'/15.5" C.).
5 P E C I FIC GRAVITY
FIG.&-PRELIMINARY
FRACTIONATIONS
Young was unable to separate the two heptanes in a very pure state by fractional distillation alone and found it necessary to resort to fractional distillation of the bromo derivatives under reduced pressure, followed by reduction. He concludrd, however, that there was little evidence of the presence of other isomeric heptanes in petroleum, and it seems reasonable to suppose that this would also hold for natural gas gasoline. Since the volumes of the frac&ns became too small for%%-ccessful handling, the heptane fractionations were not continued further. I n view of the difficulty of separating the heptanes it was considered that the separation and purities obtained were as satisfactory as could be expected under the conditions. &UANTITATIVE COMPOSITION-An estimate of the quantitative composition of this sample of gasoline may be made from the fractionation data. The measurement of the volumes of the fractions immediately after collection and again before the next fractionation gave figures on the volume losses w'hich could be classified into two kinds-evaporation losses during handling and while standing in the bottles between fractionations, and distillation losses due to the presence of liquid boiling a t or near ice temperature. This careful record of losses showed that an excessive distillation loss occurred in the preliminary and pentane fractionations, amounting in the former to 1.8 and in the latter to 3.1 times the handling and shrinkage loss, and this could be ascribed only to the escape of propane and butanes. Calculations from these lohses showed that the total propane and butane content constituted approximately 20 per cent by volume of the original sample. Assuming gasoline to be an "ideal solution," theoretical calculations based on the law of mixtures for such 14
'6
J . Chem. Soc (Loadon), 73, 906,920 (1898). [bid.,37, 73, 7G (1880).
267
a solution showed also that the maximum butane content a t 20 " C. of a gasoline with an assumed composition with respect to the hydrocarbons pentane to octane (45, 35, 15, and 5 per cent by weight, respectively) could be as high as 26.6 per cent by volume. The amount of the two pentanes was estimated from the pentane curves and the fact that the propane, butanes, a n d pentanes together constituted approximately 50 per cent by volume of the mixture. The octane and absorption oil (residues) were estimated from the preliminary curves and the fractionation data, respectively. The figures for the hexanes and heptanes were determined by difference, the relative amounts of the two being obtained from the curve for Preliminary Fractionation V. The relative proportions of the isomers in the cases of pentane, hexane, and heptane were determined from the corresponding curves. These estimates gave the following results as to the probable composition of this sample of gasoline in terms of percentage by volume: propane and butanes 20 per cent, isopentane 13 per cent, n-pentane 17 per cent, isohexane 9 per cent, n-hexane 15 per cent, isoheptane 8 per cent, n-heptane 12 per cent, octane 4 per cent, and absorption oil 2 per cent. SPECIFICGRAVITY-BOILINGPOINTRELATIONS-?vhen plotted against the corresponding boiling points in the preliminary fractionations, as shown in Fig. 5, the specific gravities give an indication of the probable presence in small amounts of the hydrocarbons, benzene and toluene. The sudden increase in the specific gravities of the fractions in the ranges 75" to 95" C. and 100" to 120" C. points to the presence of these aromatic hydrocarbons, which have higher specific gravities than the paraffins of corresponding boiling points. It is quite possible that traces of these aromatic derivatives remained in the final fractions of the hexanes and heptanes, which would account for the high specific gravities obtained for these hydrocarbons. Further investigation on this point is being carried out. ACXNOWL~GMENT
The authors desire to express their appreciation of the valuable assistance rendered by C. P. Garvey in carrying out a number of the fractionations in this work. Cyanogen Chloride-Hydrocyanic Acid Gas Fumigation The Public Health Service has for some years been seeking
a substitute for hydrocyanic acid gas for fumigating purposes,
and about a year ago called upon the Chemical Warfare Service for assistance. Chloracetophenone was first tried, and was found to give ample warning, but was so persistent as to cause annoyance, and, when used on ships, delay in returning them to duty. The use of cyanogen chloride, also a tear gas, with the hydrocyanic acid gas was then suggested. Cyanogen chloride, although it is a poisonous gas, produces lachrymation when the amount of gas is one-eighth of that which is dangerous to human beings. It is nonpersistent, but the lachrymatory effect continues sufficiently long after the concentration has ceased to be dangerous, so that fumigation with a mixture of these two gases can be accomplished with little danger to the personnel. A process for producing the mixture of hydrocyanic acid gas and cyanogen chloride on shipboard has been perfected, and this method of fumigation has been adopted by the Public Health Service. There have been many casualties in the past where hydrocyanic acid gas was used alone for fumigation. In one case in Sail Francisco where the trained men of the Public Health Service were fumigating a ship, a large number of them were overcome by the hydrocyanic acid gas and five died. Such accidents are practically impossible by the new method, which is also applicable t o buildings such as barracks, storehouses, kitchens, etc., where rats, mice, cockroaches, flies, or any other kind of vermin,*rodents, or insects are a nuisance or a menace. Amendment No. 6 to the U. S. Quarantine Regulations, Public Health Service, gives a description of the method for generating the gas and for its use in fumigation. A copy of this zmendment may be obtained upon application to the Public Health Service, Washington, D. C .
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