ANALYTICAL EDITION
July 15, 1942
533
16.
12-
a B-
4-
I
2
3 WI. % o f
4
5
6
Toluene
FIQURE5. ACIDHEATTESTDATAFOR TOLUENE-HEXA0
2
a
6
4
wt. % Ot
EYDROTOLUENE 10
12
Initial temperature, 20°,25", and 30' C.
Benzene
FIGURE4. ACIDHEATTESTDATAFOR BENZENE-CYCLOEEXANE
Initial temperature, 20°, 25',
and 30' C.
same direction. Presumably this anomalous relationship of AT to initial temperature is attributable to the relative speeds of demulsification at the different temperatures. The benzene was of reagent PURITY OF HYDROCARBONS. quality; the cyclohexane was made from it by catalytic hydrogenation under pressure a t about 135" C. The cyclohexane was shaken with nitrating acid, washed with water, and distilled. I t s freezing point of 5.9" C. indicated a purity of 99.7 per cent.
the mixture. The thermometer is placed in the thermos (bulb resting on bottom of thermos) and the temperature is read 10 minutes after stopping the stirrer-i. e., 20 minutes after the addition of the hydrocarbon. The mixture is not shaken nor stirred during the la& 10 minutes. For precise work, not only should the acid and hydrocarbon be thermostated to the same temperature, but the thermos bottle should also be at that temperature (although its heat capacity is small). The benzene content is read from the family of curves corresponding to the data in Table I, and it is to be noted that AT is essentially independent of the initial temperature (20"to 30' C.) up to 1.5 per cent of benzene. Table I1 presents acid heat data for toluene-methylcyclohexane mixtures.
TABLEI. ACID HEATTESTDATAFOR BENZENE-CYCLOHEXANE (FIGURE4) Weight Percentage of Benzene 0.00 0.56 1.08 1.56 3.29 6.38 10.15 12.01
(1)
AT from Initial Temperatures of
200 c. 0.10 1.10 2.07 2.87 5.59 10.82 17.13 20.13
25' C. 0.10 1.10 2.04 2.79 5.40 10.44 16.55 19.44
30' C. 0.10 1.09 2.00 2.70 5.22 10.07 16.00 18.75
TABLE11. ACID HEATTESTDATA FOR TOLUENE-METHYLCYCLOHEXANE (FIGURE 5) Weight Percentage of of Toluene 0.00 1.34 3.50 5.49
Literature Cited Seyer, Wright, and Bell, IND. ENQ.Cmm.,31, 759-60 (1939).
200 c. 0.32 3.96 9.71 15.00
AT from Initial Temperaturea of 25" C. 0.32 3.95 9.64 14.89
30' C. 0.32 3.95 9.58 14.80
De termination of Benzene in Cyclohexane One hundred cubic centimeters of nitrating acid (1 volume of sulfuric acid, d. 1.84, plus 2 volumes of nitric acid, d. 1.42), measured in a 100-cc. volumetric flask, are poured into a thermos bottle, the flask being allowed to drain 15 seronds. The thermometer is placed in the thermos, the bulb resting on the bottom of the latter, and the temperature is read after 2 to 3 minutes (with a ma nifying lens). Fifty cubic centimeters of hydrocarbon sample (neasured in a 50-cc. volumetric flask and a t the same temperature as the acid) are added to the acid in the thermos. An interval timer is started and the flask is allowed to drain 15 seconds. The stirrer is placed in the thermos, with the bottom of the stirring blade about 1.25 cm. (0.5 inch) from the bottom of the thermos, and when the timer reaches 30 seconds the motor is started. The stirrer is run 9.5 minutes and then removed from
CONTRIBUTION from the Koppers Multiple Fellowship on Tar Synthetics. Mellon Institute, Pittsburgh, Penna.
Cleaning Porcelain Crucibles JOHN E. D. CARWARDINE 55 Donald St., Winnipeg, Manitoba, Canada
THE
method described here can save considerable time and confusion by cleaning "burner grime" and marking inks such as ferric chloride from porcelain crucibles. It does not injure the glaze in any manner, but leaves the crucible with a perfectly clean surface. Place the crucible in a dish of fused potassium bisulfate for about 5 minutes. Remove, allow t o cool, and wash with hot water.
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