ANALYTICAL EDITION
June 15, 1943
Summary and Conclusion
Of t h e 13 acids compared as to their stabilizing effect on ascorbic acid solutions under conditions favorable to oxidation, only metaphosphoric and oxalic acids appeared suitable, these two acids being far superior t o any of the others and about equally satisfactory. It is concluded that oxalic acid may be safely substituted for metaphosphoric acid in the determination of ascorbic acid, thus providing a more stable, more easily obtainable, and less expensive extractant. Literature Cited (1) Bessey, O., J . B i d . Chem., 126, 771 (1938). (2) Bessey, O.,and King, C. G., Ibid., 103, 687 (1933), (3) Birch, T. W., Harris, L. J., and Ray, S. N., Biochem. J., 27, 303 (1933). (4) Ebihara, T., J . Biochem. ( J a p a r ~ )29, , 199 (1939).
391
Engelhardt, W. A., and Bukin, B. N., Bwkhimia, 2, 274 (1937). Fujita, A., and Iwatake, D., Biochem. Z., 300, 136 (1938-9). Krishnamurthy, P. V., J . I n d i a n Chem. Soc., 18, 201 (1941). (8) Krishnamurthy, P. V., and Giri, K. V., Ibid., 18, 191
(5) (6) (7)
(1941). (9)
Loeffler, H. J., and Ponting, J. D., IND.ENG.CHEM.,ANAL.
(10)
Lyman, C. M.,’Schktae, 13.D., and King, C. G., J . Bid. Chem.,
(11) (12) (13) (14)
Mack, G. L., and Tressler, D. K., Ibid., 118, 735 (1937). Musulin, R. R.,and King, C. G.. Ibid., 116,409 (1936). Okrent, A., and Wachhorder, K., Biochem. Z., 306, 6 (1940). Watanabe, K., J. SOC.Trop. Agr. Taihoku I m p . Univ., 8 , 381
En.. 14. 846 (1942). 118, 757 (1937).
(1937). (15) Ibid., 9,’ 162 (1937). (16) Willberg, B., 2. Untersuch. Lebensm., 76, 128 (1938). BUREAUof Agricultural and Industrial Chemistry, U. S. Department of Agriculture, Outside Publication Series No. 3908.
Apparatus for Purification of Hydrocarbons bv Recrvstallization ., J
JOHN LAKE KEAY SI, University of British Columbia, Vancouver, Canada
D
URIKG the course of an investigation into the properties
of normal paraffin straight-chain hydrocarbons, it was necessary to synthesize various homologs and to obtain them in the highest possible state of purity. Purification was accomplished principally by repeated recrystallization from glacial acetic acid, since the higher paraffin homologs are slightly soluble in this acid at boiling temperatures and quite insoluble in the acid at room temperatures. A description of the apparatus used may be of particular interest to those wishing to prepare pure hydrocarbons. I n practice, the impure hydrocarbon was dissolved by heating to the boiling point 1 to 3 grams of the hydrocarbon per liter of acid. Upon cooling, the hydrocarbon crystallized out in a mass of small, white needles. This procedure was repeated until the sample gave a constant melting point. I n some cases i t v a s found necessary t o repeat the crystallizations as many as tm-enty times, A the final melting point being approached asymptotically. I n order to facilitate the operation, which is rather cumbersome and tedious when carried out by the usual method, and to reduce the possibility of contamination from outside sources, the apparatus shown in Figure 1 was devised.
In this way it was possible to purify by recrystallization up to 15 grams of the hydrocarbon a t one time. When the acid was allowed to cool to room temperature, the hydrocarbon crystallized out and collected as a diffuse, white, cloudlike layer on top of the acid. Section F consisted of 10 em. of 2.5-em. bore Pyrex, joined to 2-mm. bore tubing. This tubing was connected through stopcock D to flask 1. The expanded section, F , was fdled with acidwashed glass wool and so packed as to provide a filter for the hydrocarbon crystals and whatever solid or insoluble impurity might be included with the sample being purified. With stopcocks C and A closed, suction was applied through B , transmitted through stopcock D, through E and F t o the bottom of flask 2. When all the mother liquor had been drawn into flask 1 from
Two 5-liter flasks were connected across a condenser, as shown. The hydrocarbon to be purified was dissolved in pure glacial acetic acid and poured into flask 2 through the condenser, vacuum being applied to the system through A and C. When this method was not practical, as in the case of hydrocarbons with high melting points, flask 2 was filled with the acid and the solid hydrocarbon was dropped down through the condenser. Flask 2 was then heated and the mixture allowed to reflux for several hours. 1
Present address, Powell River, B. C.
FIGURE 1. DIAGRAM OF APPARATUS
INDUSTRIAL AND ENGINEERING CHEMISTRY
392
flask 2, stopcocks B and D were closed, C was opened, and heat was applied to flask 1. Acid was distilled into h s k 2 until 2.5 or 5 cm. (1 or 2 inches) of impure acid residue remained m the ~~
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samples
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milliliters of acid and crystals were drawn 08: The
tube se&l ~~~~~
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its of soluble impurities. At regular interval; hydrocarbon were withdrawn from flask 2. This was
~~~~
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dicated by constant melting point, stopcocks C "aid 6 mere closed. pressure was applied through B and the impure acid was ~~~~
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flask2 into flask 1, and,
before, blom*out "through A. Flask
Vol. 15, No. 6
2 was then refilled with fresh acetic acid, heated to boiling, and the entire contents of the flask were drawn over into flask 1. From there they were drawn or blown direotly into a receiving flask. Alternatively, the Durified hydrocarbon could have been drawn directly fro&'flask-2. All passages were cleared of hydrocarbon by drawing hot acid washings down through G, up through F, E,and D,and out at A . In order to decrease the Dossibilitv of contamination from the stopcock grease, several lit& of h i t acetic acid were drawn through all stopcocks before the hydrocarbon was introduced into the system.
The apparatus was used.only for the purification of hydrocarbons, b u t it is possible that the same apparatus, or a modification in which the glass wool, F, is replaced by a selectedglass filter, could be utilized for avariety of laboratory crystallizations. It is particularly convenient where the amount of solvent is large and a number of recrystallizations are necessary.
Filtration Cylinder R. J. DEGRAY AND E. P. RITTERSIIAUSEN Soeony-Vacuum Oil Company, Inc., New York, N. Y. PI' QUANTITATIVE analysis there are times when the be filtered and washed and the filtrate brought to a required volume. At other times, the precipitate collected on the filter may require resolution, and the solution must be made up to a known volume. This is especially true in colorimetric work ( I , 2, 3). The use of au ordinary suction flask for either of these operations requires rinsing from the suction flask into a volumetric flask, with the possibility thnt thorough rinsing will give a volume larger than desired. A review of the literature showed that this problem has been evident to many. The apparatus most nearly approaching the authors' needs was one described by Yagoda (41, but this was designed for microanalysis, and no commercial source of the apparatus was indicated.
A piece of apparatus most suitahle to the authors' needs was made, and this standard volume filtration cylinder may RON be obtained from Emil Greiner, 161 Sixth Ave., New York, N. Y . The cylinder was designed to accommodate a 100-ml. volumetric flask, or a 120-ml. (Counce) sample bottle. Figure 1 shows the apparatus in this 100-ml. form. This size could be made to meet almost any need, or a 200-ml. volumetric flask could be shaped to fit the present cylinder. The letters in Figure 1 refer to the following parts: 1. A No. 3 Gooch crucihls. 2. An ordinary Gaooh crucible adapter for a suction flask. The tip of the glass tube must be dmwn out to give a fine stream. This prevents the stream from blocking the air being displaced from the volumetric flask, causing bubbling and loss of sample. 3. A special heavy rubber stopper, with a hole in the center to the (2). The Of the rests On
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applied. This construction prevents the cylinder from being split by the wedge effect of a tapered stopper. 4. Heavv elsss cylinder. 22.5 cm. (9 inches) tall and 7.5 em. (3 inches) in &side diamet&. 5. A three-way stopcock permitting suction to be applied or air introduced into the cylinder without disconnecting the suction line. In using the mpaxatus, the rubber stauuer and adaDter are removed fi%m th< cylinder. The IOO-lhI. volumetr'lc flask is placed in the cylinder, the rubber stopper replaced, and the adapter put into position, so that its stem is in the neck of the flask. A menaced Gooch crucible is olaced on the adaoter. the stopcock is t&ed to connect the suction line to the cylinber, then the filtration is made, and the precipitate is washed. When the volume of the filtrate and washings is nearly 100 ml., the suction
FIGQF~E 1
isturned off, the flask removed, and the vplume made em$ly I00 ,, , . mi. f o r WOIK wnere me volume 1s nor imporranr, a xu-mi. (4ounce) sample bottle may be used to receive the filtrate. D~
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(1) DeCray, R. J., of Lead", unpublished paper. (2) Rittershausen, E. P., and DeGray, R. J., mination of Iron". unpublished paper.
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"Colorimetric Deter-
(3) Rittershausen, E . P.,and DeGmy. R. J.. "Colorimetrir Determination of SIilfates". unpublished paper. (4) Yagoda, H., Chermist Analyst, 3, 20 (July, 1935). Pnl;snmm before the Division of Petroleum Chemistry at the IOlst Meeting of the A ~ R I C ACN :HEMICAI. SOCIETI. St. Louis, Mo.
