184
ANALYTICAL EDITION
head of a column operated a t moderate or low rate, cannot always be assumed to be filled with the vapors a t the boiling point. ADVANTAGES This stillhead is entirely of Pyrex glass, with none but glass connections. It is compact, symmetrical, relatively small, and strong, with no easily broken projecting parts. With all condenser lines suspended the head is balanced and stable, requiring no support other than the ground-glass insertion a t A . The head can be insulated completely without obscuring the internal drip-tube C, which shows the whole of the reflux. The thermometer is mounted vertically and is properly located. Two condensers are available for increasing the reflux, which may be varied up to total reflux. The construction of this apparatus, while beyond the abilities of most amateurs, is not difficult for a good glassblower. It is of course essential that the head be properly
Vol. 5 , No. 3
annealed immediately after making. Standard taper groundglass joints (8) could probably be used a t A , d, and H. LITERATURE CITED Bruun and Sohicktanz, Bur. Standards J. Research, 7, 851 (1931); Bur. Standards, Research P a p e r 379. Clarke and Rahrs, IND. ENG.CHEM.,15, 349 (1923); 18, 1092 (1926).
Fenske, Quiggle, and Tongberg, Ibid., 24, 409 (1932). Hill and Ferris. Ibid.. 19. 379 (1927). H o h e n , “Meihoden’ de; organisohen Chemie,” 3rd. ed., Vol. I, 11. 591, G. Thieme, Leipzig, 1925. ENG.CHEM.,Anal. Ed., 3 , 3 7 3 (1931). Kee:er and Andrews, IND. Les’ e and Geniesse, IND.ENG.C H ~ M1. 8, , 5 9 0 (1926). Lev*tt. Ibid.. News Ed.. 10. 268 (1932). Lovele‘ss, IN;. ENG.CH‘EM.; 18, 826 (1926). Marshall, Ibid., 20, 1379 (1928). Marshall and Sutherland, Ibid.. 19, 735 (1927). Peters and Baker, Ibid., 18, 69 (1926). Rmcnrvsn February 11, 1933.
A Method of Determining Solvent Properties of Volatile Thinners in Varnishes MIKKELFRANDSEN,~ The Cook Paint and Varnish Company, Kansas City, Mo.
V
ARIOUS tests have been designed to determine the for one hour in a water bath maintained a t 25” C. They solvent properties of volatile thinners used in the were then examined for a precipitate, which, forming a lump manufacture of varnishes: titration with the thinner a t the bottom of the tube, or adhering to the glass, was easily of a heavy-bodied linseed oil, a solution of kauri gum in recognized by slowly turning the tube upside down. To inbutyl alcohol, or a solution of a distillation residue of kauri crease the accuracy, a new series of determinations was made gum in turpentine, or gradual addition of the thinner to a between the last tube without a precipitate and the first tube short oil-kauri varnish of standardized composition as de- with a precipitate-for example, between the tubes conscribed by Holley ( I ) , until precipitation occurs. These taining 0.6 and 1.0 volumes of thinner, respectively. With tests, however, can hardly be expected to give accurate in- most thinners, the minimum volume causing precipitation, formation about the relative solvent powers of various designated as solvent power, could easily be determined with thinners in varnish bases that may contain no kauri gum at an accuracy of 10 per cent. all but instead various combinations of other resins of quite different solubilities (2). Moreover, it is to be expected that TABLEI. SOLVENT POWER OF PETROLEUM DISTILLATES other ingredients of the varnish base, such as tung oil and SAMPLD DISTILLATION RANQD SCLVDNT POWER c. linseed oil, will affect the solvent power of the thinner in the 1 37-217 0.7 mixture, because the solvent power of a mixture usually 2 38-222 0.6 3 94-174 0.8 differs widely from that calculated from its composition and 4 99-175 0.7 the solvent powers of its components. 149-188 5 1.0 144-206 0 .7 6 It seems preferable, therefore, in each case to measure the 146-222 7 0.8 147-229 0.8 8 solvent power of prospective thinners by the amount of 150-228 9 0.8 thinner that will cause incipient precipitation from the par183-249 10 0.9 184-254 11 1.6 ticular varnish base with which it is to be used. By this 0.5 12 method the writer was able to select the proper thinner for 0.6 13 a varnish in which precipitation formerly would take place 0.4 14 15 0 .6 on standing. Several difficulties, however, made an ordi0.6 16 0 . 6 17 nary titration useless. The precipitation of gum, caused 18 0.7 by adding too much thinner to the varnish base, took place 0.7 19 20 0.7 very slowly, and the varnish was so dark in color that the 21 0.7 22 0.9 precipitate could not be readily discerned; furthermore, the temperature of the solution had some effect upon the 23 99-107 0.6 107-121 24 0.7 point of precipitation. As a result, the procedure was modi121-135 0.7 25 135-149 0 .7 26 fied as follows: 149-163 0.8 27 Into each of five graduated test tubes were poured 5 to 0.8 Residue 28 10 ml. of varnish base, and the volume in each case was read off to 0.1 ml. To the five samples were then added 0.3, 0.6, Some results of this test applied to various petroleum dis1.0, 1.5, and 2.0 volumes, respectively, of the thinner to be tillates are given in Table I. Samples 1 to 11 are refined tested, and the samples were shaken thoroughly and left commercial petroleum fractions. Samples 12 to 22 were obtained by Engler distillation of sample 2, and samples 23 1 Present address, U. 6 . Bureau of Standards, Washington, D. C.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
to 28 by a similar distillation of sample 4. I n general, the solvent power of petroleum fractions toward the particular varnish base used in this investigation increases with decreasing volatility. This is definitely shown by samples 12 to 28, in spite of the small irregularity exhibited by sample 14. However, the volatility is not the only factor of influence, as shown by the first 11 samples. Sample 5 is a better solvent than sample 6 of nearly the same volatility, sample 11 is far better than sample 10, and samplp 3 is as
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good a solvent as sample 9 which has a considerably lower volatility. Such variations point to the test as a valuable guide in the selection of the best thinner.
LITERATURE CITED (1) Holley, (3; D., “Analysis of Paint Vehicles, Japans and Varniahes, p. 2, Wiley, 1920. 17, 558-67 (1925). (2) Keyes, D. B., IND. ENQ.CIIIUM., RECBIYED December 18, 1932.
A Microtest for Triaryl Carbinols AVERYA. MORTONAND LAWSON V. PEAKES,JR.,Massachusetts Institute of Technology, Cambridge, Mass.
A
COMMON indication of the presence of triaryl carbinols is the appearance of a color upon solution in sulfuric acid (3, 4). This reaction falls short of being specific since there are a number of other substances such as benzophenone (6),dibenzalacetone (6), fuchsone ( 5 ) ,and triphenylmethyl peroxide (B), which likewise give a color in sulfuric acid. I n the synthesis of certain triaryl carbinols the authors were faced with the problem of detecting traces of the desired product in the presence of a considerable amount of ketone or ester. They therefore developed an accurate test which depends on the conversion of the carbinol into the chloride and then into the free radical. The reaction was carried out in a capillary tube on a microscale in which the color of the free radical was observed readily. Moreover, as the air diffused slowly into the tube the color was discharged gradually and the insoluble peroxide was precipitated. This provided a very sensitive check on the observation of color. The method was found applicable to a number of triaryl carbinols.
PROCEDURE REAGENTS,Precipitated silver was made by the addition of zinc dust to a solution of silver nitrate. The precipitate was washed with 1 per cent sulfuric acid, with water until neutral, and then with alcohol, ether, and anhydrous ether. Since the powder still contained adsorbed water, it was covered with benzene and the latter distilled until after the distillate was no longer cloudy. It was then washed with anhydrous ether and stored in a desiccator over phosphorus pentoxide. A commercial grade, Mallinckrodt’s silver metal precipitated, was tried later in the work and found to be entirely satisfactory. Eastman acetyl chloride was used in the tests. MICROTEST. Capillary tubes, similar to melting point tubes except that they were about 1 to 2 mm. in diameter, were first made. One of these tubes was used as a reagent vessel according to the general method described by Fuchs (1). Approximately 1 mg. of the tertiary aryl carbinol was put into one of these tubes and covered with acetyl chloride. The material was stirred with a micro stirring rod made by drawing out an ordinary glass rod to a size small enough for the micro reagent vessel. After a short time the acetyl chloride was evaporated by inserting a micro tube and blowing a current of dry air over the mixture. The crystals so obtained were washed with a small amount of dry petroleum ether, using approximately the same volume as was used of acetyl chloride. The petroleum ether was admitted through a micropipet made by drawing out the tip of a dropping funnel. After stirring the crystals in the wash-
ing liquid, the tube was put into a small centrifuge to throw the chloride to the bottom. The washing liquid was then removed by means of the micropipet and a small quantity of silver powder added. Enough dry benzene to fill the tube approximately one-sixth to one-quarter full was admitted and the mixture stirred with the micro stirring rod or a fine silver-plated wire. Upon centrifuging, the silver powder was thrown to the bottom of the tube. The liquid layer remained colored from the presence of the free radical. The color could be seen better by holding the tube against a sheet of white paper or toward diffused daylight. Even when the color was only a faint yellow it was observed easily. As oxygen diffused slowly into the narrow tube the liquid became decolorized, owing to the formation of the peroxide. This effect traveled slowly downward through the tube and formed a very striking confirmation of the presence of the free radical from the carbinol. SEMI-MICROTEBT. The reaction was also carried out with 10 mg. of material in a 4-mm. outside-diameter tube. This semi-micro test was more convenient in many respects because it did not involve the use of such fragile reagent vessels, pipets, and stirring rods. Considerable latitude was found to be possible in the quantities of acetyl chloride, silver, and solvents used. The test was applied successfully to mixtures of triphenylcarbino1 with ketones and esters, and to 1 mg. of pure triphenylcarbinol. Smaller amounts were not tried. Other carbinols and halides which gave positive results were dixenylphenylcarbinol, trixenylcarbinol, cr-naphthylphenylxenylcarbinol, a-naphthylphenyltolylcarbinol, and a-bromop-benzhydryltetraphenylmethane. Negative tests were obtained with triphenylmethyl peroxide, benzophenone, and triphenylmethane. An extremely faint test was given by triphenylmethylethyl ether. Zinq dust was used in place of silver for some tests, but the latter was more active. Mercury gave erratic results, probably because of poor contact. LITERATURE CITED (1) Fuchs, Monatsh., 43, 129 (1922). (2) Gomberg, Ber., 33, 3157 (1900). (3) Kauffmann, Ibid., 52, 1422 (1919). (4) Kauffmann and Kieser, Ibid., 46, 3788 (1913). (5) Meyer, Ibid., 41, 2568 (1908). (6) Pfeiffer, “Organische Molekulverbingdungen,” 2nd ed., pp. 29,
94, Stuttgart, 1927. RECEIVEDDecember 12, 1932. Contribution No. 57 from the Research Laboratory of Organic Chemistry, Massachusetts Institute of Technology.
