JANUARY 15, 1936
through the vacuum pumps, thus preventing its accumulation. Figure 4 correlates the per cent of low-boiling oil with the difference between the open- and closed-cup flashes for mixtures of varying open-cup flashes. Lines were drawn representing various percentages of light material. For a given concentration of light oil the difference between the openand closed-cup flashes is much greater in the case of high open-cup flashes than for low ones, and for this reason the method is not satisfactory when the open-cup 0ash is below 232' C. (450" F.). Charge stocks which do not fall in the shaded area on Figure 4 are not acceptable for the nitrobenzene plant. Because of the * 5" F. errors that cannot be avoided in the flash determinations, check values should be determined in order to obtain the best accuracy. Table VI1 is typical of the accuracy that can be obtained. The light oil used for the data in this table had a 50 per cent boiling point of 229' C. and an average molecular weight of 196. 'TABLEVII. ACCURACY OF FLASH DIFFERENCE METHOD Open-Cup E%% Minus of Li h t Open-Cup Closed-Cup Closed-Cup
Oil Acfded 0.005 0.02 0.045 0.045 0.10 0.20 0.23 0.25 0.50 0.90
Flaah O F. 555 560 550 560 550 550 545 560 540 555
5
ANALYTICAL EDITION
Flash F. 555 535 510 500 485 435 440 440 390 370
Flash 0 25 40 60
fi 5 _.
115 105 120 150 185
of Light Oil Found Deviation
0 0.02 0.04 0.07 0.08 0.25 0.20 0.24 0.50 0.80
-0.005 0.00 -0,005 +0.025 -0.02 +0.05 -0.03 -0.01 0.00 -0.10
DOUBLE DISTILLATION. For stocks having an open-cup flash of 232" C. (450' F.) or lower, the preferred procedure is the double-vacuum distillation which gives a direct measure of the light oil present. This method is more accurate but more time-consuming than the flash difference method. The apparatus used for this method is very similar t o that illustrated in Figure 3 for determining nitrobenzene in oil. The &st distillation is carried out in the large-scale apparatus differing from Figure 3 only in that a 3-liter flask is used instead of a 2-liter flask, and the distillate is collected in a 100-cc. graduate instead of the 1-liter flask shown. The second distillation is carried out in a small apparatus using a 100-cc. Claisen flask, a small water-cooled condenser about 20 om. long and inclined at an angle of 45", and a small adapter similar to that shown in
Figure 3, and the distillate is collected in a 10-cc. graduate calibrated in 0.1-cc. intervals. 0" to 300" C. thermometers are-used in both distillations. When the apparatus has been assembled, a charge of about 1300 grams of the stock to be examined is placed in the balloon flask, connections and stoppers are painted with collodion or celluloid solution, and the system is evacuated to 10 mm. or less. Carbon dioxide gas is admitted through the capillary tube at such a rate that if the source of vacuum is shut off the pressure in the system will fall at the rate of about 60 mm. per minute. This corresponds to a free gas rate of about 150 cc. per minute. Under these conditions 50 cc. of the oil are distilled into the graduate, keeping the condenser temperature near that of the room. The liquid temperature in the still should never be allowed to rise above 300 C. (572" F.) in order to prevent cracking of the oil, and it is advisable to keep the temperature as far below this oint as is practical by reducing the pressure below 10 mm. The $istillation is continued until 50 cc. have been taken overhead, but in no case is a temperature of 300" C. exceeded. The distillate is then redistilled in the small set-up. In the second distillation the pressure is maintained at 10 mm. and the material distilled slowly until the vapor temperature reaches 152" C. (305" F.). The condenser is allowed to drain for 5 minutes and the volume of distillate read in the graduate to the nearest 0.1 cc. This volume represents the quantity of lowboiling oil in the weighed charge and may be converted directly t o a weight percentage basis by assuming a specific gravity of 0.8 for the distillate. If the weight-per cent of low-boiling oil is more than 0.05 per cent, the stock is not acceptable for nitrobenzene extraction. The absolute error of this method is *0.02 per cent.
Acknowledgment The authors wish to express their appreciation to J. H. Boyd, Jr., and W. A. Myers for their helpful suggestions in the preparation of this paper, to their laboratory associates for assistance in the experimental work, and to The Atlantic Refining Company for permission to publish these results.
Literature Cited (1) Anding, Zieber, and Malisoff, IND.ENG.CHEV., Anal. Ed., 6, 41 (1934). (2) Evolve, E., J. IND.ENG.CHEM.,9, 953 (1917). (3) Ferris, Birkhimer, and Henderson, Ibid., 23, 753 (1931). (4) Ferris and Houghton, Proc. Am. Petvoteurn Inst., Sec. 3,82 (December, 1932). (5) Ferns, Myers, and Peterkin, Ibid., 63 (October, 1933). (6) Intern. Critical Tables, Vol. 4, p. 153 (1928). RECEIVED October 10, 1935.
Determination of Radium in Carnotite and Pitchblende L. D. ROBERTS, University of Southern California, Los Angeles, Calif.
R
ADIUM is determined electroscopically by means of radon which is introduced into an electroscope chamber. Using a Lind electroscope the radium content of carnotite or pitchblende can be estimated accurately. In the first method proposed the ore is fused with a mixture of sodium and potassium carbonates in a platinum boat (S), the fusion dissolved in nitric acid, and the radon collected in an electroscope chamber. The objection that the fusion sometimes does not dissolve, but remains hard and glassy in the boat, is met by chilling the fusion suddenly by partly submerging the boat immediately in cold water on removal from the flame or furnace. The fusion draws away from the boat and leaves the boat while in the boiling nitric acid. In every case all the radon is removed, and the results are not low. This method gives excellent results. Barker proposed the bisulfate fusion method (1). Later
he suggested the phosphoric acid method (2), stating that i n the bisulfate method heating the fusion to drive out the radon breaks the test tubes by expanding the fusion. When the fusion is rolled on the side of the tube as the fusion cools,. the Pyrex tubes are never broken. All these methods give good results, and may be applied to any product from carnotite or pitchblende containing radium. Scott (4) gives methods for the analysis of radioactive solutions.
Literature Cited (1) Barker, H. H., J. IND. ENQ.CHDM.,10, 525-7 (1918). (2) Baumgarten, C. E., and Barker, H. H., Ibid., 15,597-9 (1923). (3) Lind, 5. C., Bur. Mines Bull. 212 (1923). (4) Scott, W. W., "Standard Methods of Chemical Analysis," N e w York, D. Van Nostrand Co., 1929.
RECEIVED November 19, 1935.
