T H E JOURNAL OF INDUSTRIAL S N D ENGINEERING CHEMISTRY
July, 1922
percentages by volume to the molecular basis were obtained by the method of Wilson and Barnardn5 I n computing the percentage composition of a blend on the molecular basis from its composition by volume, the specific gravity and the average molecular weight of each of the ingredients were
593
amount than is given in Fig. 2 . Fig. 3 shows thas on the basis of molecular concentration a somewhat lower percentage of ben7,ene is required to produce a given effect on the critical compression of a benzene-paraffin blend, as the average molecular weight of the paraffin fuel becomes smaller. But, since a relatively large amount of benzene is required to produce a given effect on the detonation factor, the actual percentage of reduction in the amount necessary with decreasing molecular weight of the paraffin fuel is not large. A simple basis for determining the amount of benzene i t is neceasary to add a paraffin fuel in order to obtain a given effect is as follows: Up to a concentration of 70 per cent by molecules, the effectiveness of benzene for suppressing detonation varies directly as the square of the molecular concentration (Fig. 3).
New Qualitative Test for Uranium’ By Harold D. Buell SYRACUSE
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UNIVERSITY,
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0 IO 20 100 90 8 0
30 40 50 60 70 80 SO 7’0 60 50 40 30 20 10
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P E R C EBY ~ MOLECULES FIG. 3-RELATIONS
BETWEEN PERCENTAGES O F XYLIDJNE B Y VOLUMF BENZENE BY MOLECULES REQUIRSDTO I M P A R T TO PARAFFIN F u E L s LIKE COMBUSTION CHARACTERISTICS FROM STANDPOINT O F DETONATION (Plotted from data in Table VII)
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employed. In view of the somewhat wide distillation range of the benzene used in the tests (Table I) a molecular weight of 79 instead of 78 was taken for benzene. The values obtained in these computations are given in Table VII.6 The curves of Fig. 3 give a more definite basis for estimating the percentage of benzene that must be added to a paraffin fuel in order to change its detonation tendency a certain 6 R . E. Wilson and D. C. Barnard, 4th, “Condensation Temperatures of Gasoline- and Kerosene-Air Mixtures,” THISJOURNAL, 13 (1921), 906. For this purpose the distillation data of the fuel (Table I) were arranged in the usual type of curve in which temperature is plotted on the vertical axis against per cent distilled on the horizontal axis. From this curve the percentages of the fuel distilling in each interval of 10’ were obtained, and these values were plotted on a chart on which the scale of the vertical axis was in terms of per cent distilled and that of the horizontal axis was in terms of temperature. The average boiling point of the fuel was taken as the point a t which a perpendicular passed through the center of gravity of the area enclosed under this differential distillation curve cut the horizontal or temperature axis. The values obtained in this way are given in Column 3 of Table VI. T h e approximate molecular weight of each of the paraffin Iuels was computed so as to bear the same proportionate relation t o the molecular weights of the hydrocarbons next above and below i t in t h e paraffin series as the average boiling point of the fuel bore to the boiling points of the normal paraffin hydrocarbons occupying like positions with respect t o it. The data used in the calculations and the value obtained for the average molecular weight of each fuel are tabulated in Table VI. 6 It is recognized that these values are only close approximations; but, in view of the wide variations between different samples of commercial gasolines, the degree of their accuracy is as great as can have any significance when dealing with such materials. Because it is such a small factor, no account was taken in making these calculations of the slight increase in volume that occurs when aromatic and paraffin hydrocarbons are blended.
SYR ICUSE, N E W
Y ORK
N testing slags and ores containing or supposed to contain uranium, it was found that when uranium was present zinc, added to a nitric acid solution of the material, gave a yellow deposit on the zinc. This test has never been recorded in the literature. It is very simple in manipulation and requires no special caution in regard to acid strength and temperature. A nitric acid solution of the sample is prepared. A large excess of acid is to be avoided because the reaction may become so violent as to boil out of the test tube and an unnecessary amount of zinc will be used up. An excess of granulated zinc is added to the solution and the reaction is allowed to proceed until the acid is spent, when a yellow deposit appears on the zinc. If the reaction is too violent the acid may be diluted; if too slow, more acid may be added. The yellow color develops more rapidly as the concentration of uranium is increased, but always appears when the reaction completely stops. The same yellow deposit was obtained from an aqueous solution of pure uranyl nitrate crystals, with no free acid present. The color did not develop, however, for two days, and the aqueous solution was acid to litmus as a result of hydrolysis. I n a solution of pure uranyl nitrate crystals with enough free nitric acid to start reaction with the zinc, it was possible to detect 0.88 mg. of uranium per cc. of solution. By concentration of the solution a more vivid color was obtained. Gold, platinum, thorium, lead, tungsten, titanium, chromium, mercury, and copper do not interfere with the test. Iron and vanadium interfere only when present in large quantities. I n the latter case, the spent liquid is removed as soon as action has ceased, and the zinc and the deposit are treated with enough nitric acid to start reaction. The deposit dissolves, but reappears when the acid is again exhausted, and vanadium and iron remain in solution. The test is not applicable in the presence of sulfuric or hydrochloric acids, when a black deposit is obtained. The yellow deposit appears only in an oxidizing solution of nitric acid, for uranyl salts are i-eadily reduced to uranous salts by nascent hydrogen. This should, however, serve as a preliminary test to indicate the presence of uranium a t the beginning of an analysis, rather than as part of a systematic scheme of qualitative separation. From the literature, it appears that the deposit is UOa.2Hz0. This is the only oxide which corresponds in color to the deposit obtained. 1
Received February 10, 1922.
