September 15,1934
INDUSTRIAL AND ENGINEERING CHEMISTRY
zation was made to phenol hthalein with nitric acid, concentrated at first and 0.25 N near t t e end. Althou h no effort was made to hurry the work, neutralization was usua!ly made within about 10 minutes after absorption. Heat liberated during neutralization was removed by cooling with tap water, to avoid decreasing the sensitivity of the chromate indicator. Then 1 cc. of M sodium bicarbonate was added, t o insure a pH of about 9, and 1 cc. of 10 per cent potassium chromate. Comparison of the titrated solution was made by reflected (not transmitted) yellowish light against a gray background with a freshly prepared reference solution containing similar amounts of reagents and a slight excess of sodium chloride. Some flasks of Pyrex glass made the yellow solution appear darker than others, an effect that appeared to be independent of wall-thickness; hence, the flasks used were matched to eliminate this effect. Titrations were continued until the reddish end point persisted for at least 5 minutes. This sometimes took 15 minutes or more, for although an apparently permanent end point was reached with the first 2 or 3 drops of 0.00818N silver nitrate, a much larger volume could be added after several minutes. The data are given in Table I.
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hydroxide absorbs phosgene very effectively and is more stable and absorbs less chlorinated hydrocarbons. The method of purification of fire-gases with zinc and mercuric sulfide (1) is preferable to the original method of purifying with silver nitrate and antimony trisulfide ( 2 ) . The principal objection to the older method-that nitric acid, formed in the removal of hydrogen chloride by silver nitrate, reacts with antimony trisulfide to give hydrogen sulfide-is obviously inoperative if the gas is passed first over antimony trisulfide and then over silver nitrate, for any hydrogen sulfide formed by reaction of the former with hydrogen chloride is removed by the latter. LITERATURE CITED
(1) Anonymous, Jahresber. &em.-techn. Reichsanstalt, 5, 11-20 (1926). (2) Fieldner, Kata, Kinney, and Longfellow, J. Franklin Inst., 190, 543 (1920). (3) Fieldner, Oberfell, Teague, and Lawrence, J. IND.ENQ. Can 11, 523, 527 (1919). TABLEI. ABSORPTIONAND SAPONIFICATION OF CHLOROFORM (4) Kolthoff and Furman, “Volumetric Analysis,” Vol. 2, pp. 211-24, APPARENT APPARENT John Wiley & Sons, N. Y., 1929. CELoR oFoR M PHOBG~NE CHLOROFORM PH00081NE (5) Kunke, J . Assoc. Oficial Agr. Chsm., 12, 264-76 (1929); C. A., P.p . m. P.p . m. P.p . m. P.g. m. 23, 4772 (1929). 0 3990 43 1000 (6) Olsen, Ferguson, Sabetta, and Scheflan, IND.ENQ.CHEM.,Anal. 3 6410 59 1410 2 6750 92 1430 Ed., 3, 189-91 (1931). 1496 1950 2510 2530
3 16 44 43
5170 10920 14S00 14600
113 153 196 190
Since, in the fire experiments (2, Table 11),the concentration of fire-extinguisher liquids varied from 2000 to 5130 p. p. m. (calculated as carbon tetrachloride) and since only about 10 per cent of this was introduced as chloroform, no error due to absorption and saponification of this compound was present. Such error, even with the more sensitive titration technic, does not begin to appear until the chloroform concentration is a t least twice the maximum introduced in the fire experiments. In the tube experiments (2, Table IV) the initial concentration of chloroform was of the order of 1400 p. p. m. But, even if it all escaped decomposition or oxidation-which could scarcely have been true, as the total concentration of chlorinated hydrocarbons decreased by about 38 per centa detectable error was unlikely, as the air samples and the absorption periods were only one-fifth or one-tenth as large as those used in obtaining the data of Table L Moreover, any possible error must have been negligible in comparison with the phosgene reported, 3700 to 3800 p. p. m. Other experiments showed that Pyrene, a typical fireextinguisher liquid (2, KO. l), was several times more resistant to saponification than chloroform, indicating that the values of 15 to 60 p. p. m. for phosgene found in fire-gases by the Bureau of Mines were not subject to any appreciable error because of chlorinated hydrocarbons introduced as fire-extinguisher liquids. The alleged high soda values obtained by other workers (6) were probably due to insufficient removal of hydrogen chloride or precipitation of silver carbonate in the Mohr titration (4). The former appears to account for the only numerical data published in support of the alleged error, which were obtained with the unpurified gas from a toluene solution of phosgene and not with purified fire-gases; the latter, for the high values obtained in experiments on the thermal decomposition of mixtures containing carbon tetrachloride, for which no numerical data were published. Such error would be the more prominent the larger the air samples taken for analysis. The soda method can be improved by acidifying with nitric acid and boiling out the carbon dioxide before neutralizing and titrating, and can also be rendered less objectionable by eliminating the use of alcohol. Aqueous N sodium
R ~ C E I V EApril D 21, 1934. Published by permission of the Director, U. 8. Bureau of Mines. (Not subject to copyright.)
A Distillation Apparatus for Phenols in Water ELDONA. MEANESAND EDWARD L. NEWMAN Wichita Testing Laboratories, Wichita, * Kans.
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HE apparatus illustrated was designed for the steam distillation of phenols from water solutions, and is simpler and more compact than the usual type. Instead of the box with a series of tubes and connections as described by Shaw (I), the outfit is condensed into a single unit. This consists of a glass tube, A , divided into two compartments B and C. In part B is placed distilled water and in art C is placed the sample to be distilled. ThrougR an inner tube fitting down into the lower compartment a slow stream of washed air is passed. The air becomes saturated with moisture and passing up is deflected down through the sample, releasing its moisture and maintaining a fairly c o n s t a n t volume. The tube is surrounded by a glass jacket. Steam, generated in flask D,passes up around the tube and escapes at the top, maintaining the temperature for distillation of the sample. The phenols present are thus distilled over and are condensed and collected in a graduated cylinder. Connections with which the vapors come in contact are made by means of ground-glass stoppers. No rubber tubes or stoppers are used, thus eliminating any possible contamination.
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Any suitabIe indicator may be used to ascertain the amount of phenol in the distillate. LITERATURE CITED (1) Shaw, J. A,, IND.EKG.CHEM.,Anal. Ed., 1, 118 (1929). RBCEIYED July 11, 1934.
