I S D L - S T R I A L -4-1-D ESGIA1-EERISGCHEMISTRY
July, 1925
75 1
Determination of Minute Amounts of Phenols in Polluted Natural Waters’ By Loren R. Vorce C l r Y IJF
c L E \ B 1 . 4 1 0 D E P ’ 4 R T M E I S T O F PUBLIC W E L F A R E ,
ARLY in 1924 the writer was asked to analyze the water of the Cuyahoga River, in order to determine the amount, if any, of phenols present. Sone of the known methods were sufficiently delicate for this purpose, and after extensive experiment the following method was evolved. It requires no special apparatus, no particularly skilled technic, and is capable of easy execution Tvith the equipment of the average chemical laboratory.
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Method
PREPARATION OF Ss?mLE-Measure accurately 2 or 3 liters of the sample into a flask, add 2 to 4 grams of solid caustic soda, and shake frequently until dissolved and the precipitated bases and coagulated albuminous matter have separated. Filter into a similar flask, wash flask, and filter once with water. To the filtrate in the second flask add 25 cc. of peroxide of hydrogen (H202), being particular to use a kind stabilized with a compound that does not contain a benzene nucleus. Shake thoroughly and allovv to stand overnight, uncorked, to allow as much as possible of the excess peroxide to escape. Fit the flask ivith a rubber stopper carrying a constant-level delivery tube. Place :It least 20 grams of solid sodium hydroxide in a 15-em. nickel or porcelain evaporating dish,2 and if 1 liter of the sample was taken support on a stand over a Bunsen burner. If 2 or more liters of the sample were taken, place the dish on a constantlevel water bath and run overnight. Support the inverted flask over the dish so that the level of water in thcl dish will maintain a nearly constant yolume of not more than 200 cc. Adjust the burner (case of 1-liter sample) so that the contents of the dish are just below the boiling point. TVheri the flask is empty, rinse it and the delivery tube once or twice with water and continue evaporation until the contents of dish do not exceed 200 cc. Transfer the concentrated solution to a long-necked, 750cc. Kjeldahl flask, and chill in ice or cold tap water. Add to the flask, all a t once, 45 grams of crystallized citric acid and, when dissolved, test with litmus paper to insure acidity. Fit the neck of the flask with a rubber,stopper carrying a return-flow bulb trap with vapor outlet tube bent downward to fit the top of the vertical condenser, and a glass stopcock separatory funnel of 50 to 75 cc. capacity. Any form of condenser that will deliver the distillate thoroughly cold will suffice. If the projecting bottom end of the condenser tube is not long enough to reach the bottom of an ordinary 500-cc. volumetricflask, extend it with a rubber sleeve and glass tube. Connect the distilling flask to the condenser and place below, on sufficient blocking, a 500-cc. volumetric flask as receiver, first adding a few cubic centimeters of water to seal the end of the condenser tube. Heat the distillation flask by a direct flame and distil until about 125 cc. have passed over, when the contents of the distilling flask will be almost entirely sodium citrate dissolved in its crystal water. Lower the receiver until the tip of the condenser tube is again just sealed by the distillate, and without removing the burner introduce through a stopcock funnel 100 cc. of distilled water. Continue distillation and repeat this procedure each 1
2
Received January 31, 1925 K E Edball, J r , i n p r i l a t e
H E A L T H , CLEVELAWD,
OHIO
time 100 cc. have distilled over until the receiving flask is nearly filled to mark. After allowing the distillate to reach room temperature, make up to 500 cc. with distilled water and mix thoroughly. This solution now contains all but traces of the phenol in the sample originally measured into the reseryoir flask of the concentrating apparatus. PREPARATIOXS OF PHESOL RmGEm-The phenol is determined colorimet’rically by the Folin and Denis3 phenol reagent, prepared as follows: To 750 cc. of distilled water add 100 grams of sodium tungstate, 18 grams of molybdenum trioxide, and 50 cc. of 85 per cent phosphoric acid (&Pod), and boil under the reflux condenser for 2 hours. Cool and dilut’e to 1 liter.4 The standard phenol solution contains 1 mg. phenol to 1 cc. solution and is preserved in a black, paper-covered, glass-stoppered bottle with the stopper kept sealed by wax and the bottle kept away from light as much as possible. Thus preserved the solution will keep a t least 6 months without change of strength. COLORCOMPARISOX-FO~ the color coniparison standards, some of this strong standard is diluted to a 10 p. p. m. solution for use in making up t’he color standard tubes; this 10 p. p. m. solution should be freshly prepared each time as it does not keep well. The writer uses 50-cc. Kessler tubes for the comparison, and in making the color standards, in 50-cc. tubes, 1 cc. of the Fohn and Denis phenol reagent should be added for each 1 p. p. in. of phenol in the standard, and followed by 5 cc. of saturated sodium carbonate solution. At least an hour is required for full development of color in tubes of less than 4 p. p. m. of phenol, and wit’hniore than 4 p. p. m. of phenol the sample must be diluted for comparison. Tubes are best viewed from the side against a white background, by reflected light. Khen the color standards have fully developed, t’he sample tube, prepared a t same time as standards, is compared with them and the indicated content noted. If this indicated cont’ent of phenol in parts per million varies from the number of cubic centimeters of phenol reagent used in preparing the sample tube, make up two more tubes of the sample distillate, using in one as many cubic centimeters of phenol reagent as the parts per million of phenol indicated by the trial tube, and in the other, 0.5 cc. more than the indication. These two tubes will almost always give so nearly the same color that they cannot be distinguished from each other. If either should be visibly darker, compare the darker one with the color standards and take the reading as the phenol content of the distillate. Calculation to original sample is obvious. Results
By this method and using equipment as described above, the following results were obtained upon Cuyahoga River water, to which E. B. Buchanan, of the Bacteriological Laboratory of this division, had added known amounts of phenol, submitting samples to writer, “unknown,” for analysis. SAXPLE Phenol actually added Added phenol found 3
communication
DIVISIOX OF
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3.00 8.26
J . Bioi. Chern., 12, 239 (19121. Scott, THISJ O U R X A L . 13, 422 (1921,
PARTSP H R MILLION--B C D 0.5 1.10 0.50 0.5 1.00 1 00
E 0.23
0.20
