found in air; the hexene w m selected t o simulate any olefinic material that could possibly compete for the collected ozone. The results show that none of the interfering substances tested caused either a positive or negative interference greater than 5.0%. Because this value is within the limits of the precision of the method, none of these substances interfere and the method is specific for ozone in the atmosphere. APPLICATION
The pyridylethylene and the neutral potassium iodide procedures were simultaneously applied to the analysis of ozone in both ambient atmospheres and irradiation chambers. I n controlled atmospheres, where substances that interfere with the potassium iodide procedure were absent, good agreement was obtained between the
methods. I n atmospheres oontrrining substances known to interfere with the potassium iodide procedure, agreement between the methods was not always good, although the pyridylethylene procedure gave fairly reproducible results. This nonagreement was attributed to the erratic results obtained with the potassium iodide procedure. Limited application in the analysis of ambient atmospheres outside the window of our laboratory showed fairly good agreement between the procedures, with the pyridylethylene procedure always giving slightly higher ozone concentrations. A more detailed investigation into the field applicability of the pyridylethylene procedure for air pollution surveys is currently being pursued. LITERATURE CITED
(1)Altshuller, A. P., Schwab, C. M., Bare, M., ANAL.CHEM.31,1987 (1959).
S., Chem. Rev. 58, 925 (1958). (3) Bravo, H. A., Lodge, J. P., ANAL, CHEM.36, 671 (1964). (4) Byem, D. H., Saltzman, B. E., Am, Ind. Hy Aseoc. J. 19, 251 (1958). ( 5 ) Long, Jr., Chem. R y . 27,437(1940). (6) Public Health Service Publication NO. 999-AP-11, pp. D-1, E-1, USDHEW, R. A. Taft Sanitary Engineering Center, Cincinnati, Ohio
(2) Baily, P.
c.,
(lQR.5 ). \ - - - - I -
(7) Saltzman, B. E., Gilbert, N.,ANAL. CHEM.31, 1914 (1959). (8) Saltzman, B. E., Wartburg, A. F., Ibid., 37, 779 (1965). (9) Sawicki, E., Hauser, T. R., Stanley, T. W., Elbert,. W.. . ANAL. CHEM.33, 93 (1961). (10)Sawicki, E., Stanley, T. W., Hauser, T. R., Chemist-Analyst 47, 31 (1958). RECEIVEDfor review May 9, 1966. Accepted June 23, 1966. Division of Water, Air, and Waste Chemistry, 152nd Meeting, ACS, New York, N. Y., September 1966. Mention of commercial products does not imply endorsement by the Public Health Service.
Fujiwara Reaction and Determination of Carbon Tetra c hI o ride, ChI o rof o rm, Tetrachloroethane, and Trichloroethylene in Air G. A. LUGG Department of Supply, Defence Standards Laboratories, Australian Defence Scientific Service, Maribyrnong, Victoria, Australia The system pyridine-sodium hydroxide-water has been examined as it applies to the development of color with chlorinated hydrocarbons using the Fujiwara reaction. Methods for the determination of carbon tetrachloride, chloroform, s-tetrachloroethane, and trichloroethylene in air are presented employing both twophase and one-phase procedures. Carbon tetrachloride can be determined if a ketone is present. Absorption studies of the compounds in pyridine have shown that at least 90% of the vapors can be collected in two bubblers. Data are given on the precision, accuracy, and specificity of the methods.
T
Fujiwara reaction (10) is the classical method for determining a large number of halogenated hydrocarbons. It is characterized by the red color developed when the halogen compound is heated with sodium hydroxide and pyridine. Two absorption bands are formed, one at 368 mp, the other initially at about 535 mp. The reaction has been used for determining the concentration in air of carbon tetrachloride (4, 7 , 9, 15, 17, 20, 21, 25), HE
1532
ANALYTICAL CHEMISTRY
chloroform (7, 12, 15, 17, 18), tetrachloroethane (16, l 7 ) , and trichloroethylene ( 3 , 5 , 1 5 , 1 7 , 2 5 ,ad), and for the determination or detection of these and other polychloro compounds in body fluids and other media. Ross (22) attributed the reaction to compounds containing the general formula RC(halogen)8. Webb, Kay, and Xichol (25) stated that, in general, compounds containing only two halogen atoms per molecule, or a maximum of two on any one carbon atom when more than two halogen atoms per molecule were present, showed much less sensitivity than the compounds having three halogen atoms attached to the same carbon atom. Contradictory statements have appeared on the reaction conditions required for carbon tetrachloride (6, 14, 16). Bromo compounds (25) and iodo compounds (22) have been detected by the reaction, but there are no reports on fluoro compounds. Generally, absorption spectra have been determined using the pyridine layer separated from the caustic layer after development of the color with a two-phase procedure, but some investigators have used solvent to dilute the mixture to avoid the two phases (1 , 11).
Rogers and Kay (21) were the first to use a one-phase procedure of pyridinewater-sodium hydroxide, and this method was subsequently used by other workers (4, 6, 13, 17, 23). The Fujiwara reaction has had numerous modifications: These have involved the solvents, the concentration and relative amount of sodium hydroxide, the time and temperature of heating, the time of standing before absorbance is measured, and the wavelength at which it is measured. Most of the accounts refer to the necessity of adhering strictly to the stated amounts of the reagents and the conditions of heating, but it is not possible to define clearly the optimum conditions for the reaction from the published work on the subject. For this reason an investigation of the method was undertaken, particularly as it applied to the determination of chloroform, carbon tetrachloride, trichloroethylene, and tetrachloroethane in the air. EXPERIMENTAL
Throughout the experimental work, 1-em. cells were used and the volume of pyridine was standardized a t 5 ml., as this is a convenient quantity for use with these cells. All work carried out
taking 0.0, 1.0, 2.0, 3.0, and 4.0 ml. of the standard solution, making up to 4.0 ml. with pyridine, and treating the solution as in the respective method. RESULTS AND DISCUSSION
% NaOH In Pyridine Figure 1. Absorbance as a function of sodium hydroxide in pyridine containing 20% water
with tetrachloroethane refers to the symmetrical isomer. Apparatus. The recorded spectra were obtained on a SP700 spectrophotometer; all other measurements were made on a SP500 spectrophotometer. Both instruments are manufactured by Unicam, Cambridge, England. ,411 absorbance measurements were made using water as the reference liquid. Reagents. India gum solution, British Drug Houses pulverized India gum, 1% soiution, in water. Pyridine, analytical reagent. Sodium hydroxide solution, molar strengths of analytical reagent grade as specified. Methyl ethyl ketone, purified by standing over potassium permanganate and distilled. One-phase sodium hydroxide reagent. Dissolve 1.15 grams of sodium hydroxide in 1 liter of water. Pyridine-methyl ethyl ketone solution. Dissolve 10.0 ml. of methyl ethyl ketone in pyridine and make up to a volume of 100 ml. Sodium hydroxide-methyl ethyl ketone solution. Dissolve 1.15 grams of sodium hydroxide in water, add 100 ml. of methyl ethyl ketone, and make up to 1 liter with water. Recommended Analytical Procedures. Charge bubblers of the midget impinger type with 5 ml. of pyridine, connect in series, and take an air sample of the volume shown in Table I. Use calibrated critical orifices to control air flow. After sampling, draw the solvent a few times up the inlet tube, withdraw the sampling head, and make the volume up to 5 ml. with pyridine. TWO-PHASE METHOD. For chloroform, trichloroethylene, and tetrachloroethane, add sodium hydroside to the sampling tube (both the volume and concentration are listed in Table I). For carbon tetrachloride add 4.0 ml. of the sampling solution, 5 ml. of 10.7511f sodium hydroxide, and 1.0 ml. of pyridine-methyl ethyl ketone solution to a 6 x 1 inch test tube. Stopper the tubes, shake vigorously, loosen the stoppers, and heat the solutions in a boiling water bath for the period shown u
in Table I, place in a cold water bath for 5 minutes, and separate the layers. For tetrachloroethane and trichloroethylene, add 0.5 ml. of India gum solution to the pyridine layer and shake. Measure the absorbance at the wavelength shown in Table I. ONE-PHASEMETHOD. Pipet 4.0 ml. of sampling solution into a 6 X 1 inch test tube and add 1.0 ml. of the onephase sodium hydroxide reagent. For carbon tetrachloride use 4.0 ml. of sampling solution and 1.0 ml. of sodium hydroxide-methyl ethyl ketone solution. Mix and heat in a boiling water bath for the period shown in Table I. Cool for 5 minutes in a cold water bath, add 0.5 ml. of India gum solution, shake, and measure the absorbance. CALIBRATION.Prepare a standard solution of the maximum amount stated in the concentration range in Table I in the volume of pyridine stipulated. These solutions are stable for a t least one month. For the two-phase methods for chloroform, trichloroethylene, and tetrachloroethane, obtain a standard curve by taking 0.0, 1.0, 2.0, 3.0, 4.0, and 5.0 ml. of the standard solution, making up to 5.0 ml. with pyridine, and treating the solution as in the twophase method. For all one-phase methods and for the two-phase method for carbon tetrachloride, obtain a standard curve by
Table 1.
Substance Carbon tetrachloride Chloroform
Effect of Sodium Hydroxide and Water in Pyridine Phase. Although the Fujiwara reaction can be carried out in a two-phase system consisting of a layer of aqueous sodium hydroxide in contact with a layer of pyridine, in this method the concentration of both water and sodium hydroxide in t h e pyridine phase varies simultaneously with volumes and concentrations of aqueous sodium hydroxide solutions used, and it is not possible to distinguish their independent effects on the development of color. The effect of sodium hydroxide was studied by carrying out the reaction by a one-phase method with 5 ml. of pyridine containing 0.05 mg. of chloroform, 20% water, and concentrations up to o,02570 of sodium hydroxide; the last solution was slightly cloudy because of undissolved sodium hydroxide. The results are shown in Figure 1; optimum absorbance is given with 0.023% sodium hydroxide and this is the maximum amount of sodium hydroxide which can be present in solution when 20% water is present in the pyridine. The influence of water was shown by carrying out the reaction with 5 ml. of pyridine containing 0.05 mg. of chloroform, 0.023% sodium hydroxide, and 20, 25, 30, 35, and 40y0 water. The results are shown in Figure 2 ; the highest absorbance was obtained with 20y0 water and this is the minimum amount possible when 0.023% sodium hydroxide is present. The results show that the color intensity is reduced by water and intensified by sodium hydroxide; these conditions are best met in equilibrated solutions of sodium hydroxide solution and pyridine which contain the maximum ratio of sodium hydroxide to water possible in the pyridine layer.
Analytical Data
Sodium HeatBlank ~i~ hydroxide Ing Concn. abM.A.C., p.p.m. Proce- Sam le, M , Vol.,period, E X, range, sorbpg.* ance ( 8 ) durea mf concn. ml. min. Amax 195 535 4 9 5-100 0 . 0 2 10 I 2000 50
Tetrachloroethane
5
Trichloroethylene
100
I1 I I1 I 11 I 11
2000 200 300 5000 3000 500 300
l0:75 10:75
'5
..
5
6:25
io
6:25
io
5 2 5 5 2 5 2
535 4 5 5-100 535 12.5 2-50 535 8 . 9 2-50 535 2 . 5 10-200 470 5 . 1 5-100 535 2 . 3 20-150 470 4 . 2 5-150
0 02 0.02 0.02 0.02 0.04 0.02 0.04
I, One- hase. 11, Two-phase. * In 4 mf of p ridine, except two- hase procedure for chloroform, tetrachloroethane, and trichloroethycne in 5 ml. of pyriine. a
VOL 38, NO. 1 1, OCTOBER 1966
1533
20
0
25 %H,O in Pyrldinc
30
35
40
Figure 2. Absorbance as a function of water in pyridine containing 0.023% sodium hydroxide Development of Color. Pyridine containing the same concentration of water and sodium hydroxide as the equilibrated pyridine layer of the two-phase method can be prepared for a one-phase method either by separating from the aqueous phase or by dissolving the requisite amount of water and sodium hydroxide. Figures 3 and 4 show, with the onephase and two-phase methods, respectively, the absorbance obtained with 0.05 mg. of chloroform as a function of the volume and concentration of the sodium hydroxide phase. For the onephase method, 1 ml. of pyridine containing the chloroform was added to 5 ml. of the separated pyridine phase prior to carrying out the reaction. For both methods the solutions were heated for 2 minutes at 100' C. and the absorbance was measured a t 535 mp. When the concentration of sodium hydroxide is less than 6 . 2 5 X for the onephase and 10.75X for the two-phase method, the absorbance increases until it reaches the maximum and then decreases, because of increasing water concentration in the pyridine phase. With sodium hydroxide solutions of 6.25M for the one-phase and 10.75M for the two-phase method, the absorbance rises until it reaches the maximum and then remains constant because the water and sodium hydroxide concentration in the pyridine phase Temains unchanged. With concentrations in excess of 6.25X for the one-phase and 10.75.1.1 for the two-phase, the absorbance increases but never attains the maximum reading, as insufficient water, and hence sodium hydroxide, is present in the pyridine phase. All pyridine solutions which give an absorbance of 1.05 with the one-phase method as shown in Figure 3 contain 0.023% sodium hydroxide and 20% water. All volumes of sodium hydroxide solution which give an absorbance of 0.88 with the two-phase method as shown in Figure 4 contain 0.0017% sodium hydroxide and 7.0% 1534
0
ANALYTICAL CHEMISTRY
water in the pyridine phase. Concentrations of either sodium hydroxide or water differing from these amounts lower the absorbance. Reference to Figure 4 shows that 5 ml. of 10.75M sodium hydroxide will give maximum color intensity; it is also a convenient quantity to use. The reason for the lower requirement of sodium hydroxide concentration in the two-phase procedure is that more can be supplied from the aqueous layer as required during the course of the reaction. Therefore, although the onephase method is convenient and rapid, color formation will be depressed when excess chlorinated hydrocarbon is present, because of insufficient sodium hydroxide. It is thus possible for the same absorbance reading to be obtained from a high and low concentration of the compound. The single-phase method should be used only when the concentration to be determined is known approximately. Solvent Effect. The optimum concentrations of water and sodium hydroxide in the pyridine phase were determined using pyridine as a solvent for chloroform. The effect of other solvents was obtained by adding 1 ml. of the solvent containing 0.05
mg. of chloroform to 5 ml. of pyridine and carrying out the reaction using the two-phase method, heating for 2 minutes. The results showed that for most solvents the optimum concentration of sodium hydroxide solution is lowered to about 6.25M; this is possibly due to solvents decreasing the solubility of water and sodium hydroxide in pyridine. The results also indicated that polar solvents are not suitable for developing the color; nonpolar solvents are usually satisfactory but are not superior to pyridine itself. Ketones reduce the color and aldehydes inhibit it altogether. Effect of Time and Temperature of Heating. Heating a t 100' C. gave the most rapid development of color. The intensities of the various bands obtained with 0.05 mg. of chloroform are dependent on the time of heating. The 535-mp band is at a maximum intensity with 2 minutes' heating for the one-phase and with 5 minutes' heating for the two-phase methods. The absorbance at 368 mp increases with the time of heating. Color Stability. After development of the color the resulting pyridine solutions obtained with the one-phase method are cloudy. This cloudiness can be removed by adding more pyridine or solvents such as alcohol or water. The most satisfactory procedure has been found to be adding a solution of gum. The colors are stable for at least 15 minutes before and after the addition of gum. If 10.75.11 sodium hydroxide is used for the two-phase method, the solutions are clear and do not require gum. Both before and after separation of the phases, the color was stable for at least 15 minutes. Optimum Conditions for Carbon Tetrachloride. Carbon tetrachloride does not produce a color in the reaction with sodium hydroxide and pyridine alone, but it does if a ketone is present. With acetone and methyl ethyl ketone a band additional to those at 625M
5M 75M W
4
0 ml NaOH
Figure 3. Absorbance as a function of volume and concentration of sodium hydroxide solution 0.05 mg. of chloroform with one-phase method
tQ
368 and 535 mp appears at about 320 mp. In the presence of ketones this band also appears when chloroform is used to obtain the color but not when trichloroethylene or tetrachloroethane is used. Other ketones can be used to develop the reaction with carbon tetrachloride in the following order of decreasing activity: methyl ethyl ketone, acetone, cyclohexanone, acetophenone , o-methyl benzophenone, and benzophenone. With methyl ethyl ketone maximum color intensity is produced when 0.1 ml. of the ketone is added to 5 ml. of pyridine, and smaller quantities produce lower absorbance. With carbon tetrachloride, absorbance plotted as a function of the volume and concentration of sodium hydroxide showed patterns similar to Figures 3 and 4. I n these cases 0.1 ml. of methyl ethyl ketone was added to the 5 ml. of pyridine and optimum results were obtained with 6.25M sodium hydroxide with the one-phase method and 10.75M with the two-phase method. Highest absorbance readings resulted from 5 minutes’ heating with both methods. Optimum Conditions with Tetrachloroethane and Trichloroethylene. When these two compounds, dissolved in pyridine, are heated with sodium hydroxide, two bands similar to those from chloroform appear a t 535 and 368 mp. As the time of heating is increased, the 535-mp band changes and a more stable band appears a t 470 mp. I n the one-phase method, maximum absorbance is given with pyridine equilibrated with 6.25M hydroxide, the 470mp band is still not prominent u p to 5 minutes’ heating, and maximum absorbance a t 535 mp is obtained with 5 minutes, heating. However, with the two-phase method, the band shifts more quickly and although the higher absorbance readings are obtained at 1-minute heating a t 535 mp using 10.75M sodium hydroxide, the absorbance obtained at 470 mp with 2 minutes’ heating using 6.25M sodium hydroxide is more stable; the latter was selected for use with the two-phase method and in this case it was necessary to add gum to clarify the solutions. Sampling Efficiency. The vapor of the compounds was set u p in concentrations of the order of the maximum allowable concentration (2) using a diffusion cell similar to a type previously described (19). Sampling was carried out at 100 ml. per minute through three bubblers in series until a volume of air shown in Table I was taken. The samples were analyzed using the two-phase method; where necessary, the solutions were diluted with pyridine before analysis. The results shown in Table I1 indicate that at least 90% of the vapor is absorbed in two bubblers.
-
r5 w
5QM.
P
I
ll
24
5’
’
IO
I5
25
20
rnl. of NaOH
Figure 4. Absorbance as a function of volume and concentration of sodium hydroxide solution 0.05 mg. of chloroform with two-phose method
Precision and Accuracy. The plot of absorbance against concentration was linear over the quoted range for all the compounds and both analytical methods. T h e precision of each of the methods was tested by quintuplicate analysis with known solutions a t each of five concentrations. All results were referred to the same calibration curve for each compound. The standard deviation, relative standard deviation, and relative error for each set of analyses are reported in Table 111. The reproducibility appears to be of the same order throughout, while the one-phase procedure seems more accurate for the carbon tetrachloride and chloroform and the two-phase
Toble
II.
procedure more accurate for tetrachloroethane and trichloroethylene. At the end of the reaction, the 368-mp band is of greater intensity than the 535mp band and it would be advantageous to use it for determining compounds which give low absorbance in the visible region. This could be done by measurement in the ultraviolet or by conversion to a colored derivative with dimedon, indole, or l-phenyl-3-methyl-5-pyrazalone. For the compounds investigated here, the absorbance in the visible region is adequately sensitive. Specificity. Table IV lists compounds which will give the reaction using the two-phase procedure for chloroform. Chloroform, along with
Sampling Recovery and Efficiency
Absorption, Substance Chloroform
Carbon tetrachloride
Tetrachloroethane
Trichloroethylene
Nominal concn. mg./cu. m.
1st bubbler/ nominal
205 247 324 489 602 36 65 79 110 140 26 21 40 75 86 220 270 443 528 794
68.0 65.5 67.1 72.0 68.4 72.6 61.7 74.8 75.9 74.7 83.1 85.3 86.0 83.9 85.0 83.0 78.2 81.8 80.0 81.6
1st and 2nd
bubblers/ nominal 94.3 91.2 92.5 94.0 92.7 92.6 90.8 93.8 92.9 93.7 97.5 97.6 97.1 98.0 97.5 96.7 97.3 97.0 97.0 96.8
VOL 38, NO. 1 1 , OCTOBER 1966
1535
Table 111.
Compound
Procedurea
I1
I
Chloroform
I1
Tetrachloroethane
I
Precision and Accuracy
Concn.,
10.0 16.0 30.0 44.0 6.0 15.0 28.0 34.0 42.0 30.0 75.0 140 170 210
Std. dev. 2.01 1.76 1.70 2.63 2.87 1.48 2.35 1.95 2.65 2.95 0.32 1.67 0.44 1.87 1.93 0.32 0.95 0.87 0.36 0.82 2.46 3.70 2.55 3.31 5.40
30.0 75.0 140 170 210 30.0 56.0 68.0 84.0 170
2.78 1.99 2.75 2.85 1.73 3.90 10.07 8.4 7.0 1.14 1.47 1.56 0.82 7.18
pg.b
24.0 60.6 112 136 168 6.0
Rel. std. dev. 8.5 3.0 1.5 1.9 1.7 6.1 4.0 1.8 2.0 1.8 5.3 4.1 2.8 1.6
4.3 5.3 6.1 3.1 1.0 1.9 7.7 4.4 1.9 2.0 2.5 10.1 9.3 3.5 3.7 3.1 5.9 5.0 7.2 4.8 3.3 3.9 2.7 2.3 1.0 4.3
1.18
Trichloroethylene
I
I1
Rel. error, yo 0.2 0.6 0.9 0.3 0.1 4.8 2.8 1.2 1.5 1.3 0.1
Table IV. Sensitivity of Compounds Which React to Give Fujiwara Reaction
1.8
0.1 0.5
0.1
4.6 5.1 2.7 2.8 1.2 3.3 3.4 1.5 1.3 2.0 0.4 0.01 0.1 3.2 2.6 4.1 3.6 5.4 1.3 1.7 0.4
0.4 0.3 0.3 3.5
I, one-phase; 11, two-phase. In 4 ml. of pyridine, except two-phase procedure for chloroform, tetrachloroethane, and trichloroethylene 5 ml. of pyridine. 11
b
@
Compound € Trichloroacetic acid Chloroform Chloral hydrate Tribromoethylene Bromoform Tetrachloroethane Carbon tetrachloride Trichloroethylene Carbon tetrabromide Benzotrichloride 1,1,l-Trichloroethane Benzal chloride Dichloroacetic acid Tetrachloroethylene Pentachloroethane Iodoform Hexachloroethane Methyl ethyl ketone added.
x 10-8 11.4 8.9 8.7 7.2 5.7 5.2 4.5“ 4.2 3.2 0.8 0.5 0.4 0.3 0.2 0.15 0.1 0.05
(4) Belyakov, A. A., Zavodsk. Lab. 23, 161 (1957); C. A. 51, 17606c (1957). (5) Brain. F. H.. Analvst 74.555 (19491. (6j Burke, T. E., Souihern; H. K.,I k . , 83,316 (1958). (7) Daroga, R. P., Pollard, A. G., J. SOC. Chem. Znd. 60,218 (1941). (8) Dyson, G. &“Manual I., of Organic Chemistry for Advanced Students,” Longmans-Green, London, 1950. (9) Fabre, R., Truhaut, R., Laham, S., Ann. Pharm. Franc. 9, 251 (1951); C.A. 45,9100f (1951). (10) Fujiwara, K., Sztzjer. Abhandl. Naturjorsch. Ges. Rostock 6, 33 (1914). (11) Gettler, A. O., Blume, H., Arch. Pathol. 11, 554 (1931). (12) Grabowicz, W., Chem. Anal. (Warsaw) 5, 1027 (1960). (13) Griffon, H., Mossanen, N., LegaultDemare, J., Ann. Pharm. Franc. 7, 578 (1949); C.A. 44, 306521 (1857). (14) Hildebrecht, C. D., ANAL. CHEM. 29, 1037 (1957). (15) Hunold, G. A., Schuhlein, B., 2. Anal. Chem. 179, 81 (1961); Chem. 179, 81 (1061); C.A. 55, 9162; (1961). (16) Jenovskv. “ , L.. Chem. Lzstv 1 48.. 1419 (1954). (17) Krynska, A,, Prace. Cent?. Inst. Ochrony. Pracy. 10, 186 (1960); C.A. 58, 4963f (1963). (18) Kubalski, J., Acta Polon. Pharm. 10,269 (19.53); C . A . 48, 10492f (1954). (19) hIcKelvey, J. M., Hoelscher, H. E., ANAL.CHEM.29, 123 (1957). (20) Itamsey, L. L., J . Assoc. O$lc. Agr. Cheinists 40, 175 (1957). (21) Rogers, G. R., Kay, K. K., J . Znd. H y g , Tozicol. 29, 229 (1947). (22) Ross, J. H., J . Biol. Chem. 58, 641 (1923). (23) Stack, V. T., Jr., Forrest, D. E., Wahl, K. K., Am. Ind. Hyg. Assoc. J . 2 2 , 184 (1961). (24) Truhaut, It., Ann. Pharm. Franc. 9, 175 (1951); C. A . 45,8072g (1951). (25) Webb, F. J, Kay, K. K., Nichol, W. E., J . Ind. H y g . Tozicol. 27, 249 (1945). I
~
chloral hydrate and trichloroacetic acid, gives the most intense color. I n the absence of P, solvent the three compounds give rise to identical specta at 368 and 535 mp. Lower in intensity are trichloroethylene and tetrachloroethane. Tetrachloroethylene behaves like these last t w o compounds with the 535-mp band displaced to about 470 mp on heating but is considerably less sensitive. Of the dichloro compounds tested, all gave bands at about 368 mp. Weak bands are given by ethylene chloride at 535 mp and benzal chloride at 480 mp; these last two bands are not due to chloroform impurities, as no bands appear a t 320 mp in the presence of acetone. Dichloroacetic acid and ethylidene dichloride give a weak band at 535 mp but ethylene dichloride gives no band in this vicinity. Ethyl chloride also gives a band at
1536
ANALYTICAL CHEMISTRY
368 my and on prolonged heating (60
minutes) a further band appears at about 470 mp. Bromoform and tribromoethylene give absorption spectra corresponding very closely to chloroform and trichloroethylene with only a slight reduction in intensity. Carbon tetrabromide gives an absorption spectrum closely corresponding to bromoform; unlike carbon tetrachloride, a ketone is not required, since the carbon tetrabromide can be converted to bromoform by the action of alkali (8). LITERATURE CITED
(1) Adams, W. L., J . Pharmacol. 74, 11
(1942)..
(2) American
Conference of Governmental Hygienists, Arch. Enuiron. Health 1,592 (1963). (3) Barrett, H. M., J . Ind. Hyg. Tozicol. 18, 341 (1936).
RECEIVED for review March 21, 1966. Accepted June 27, 1966. Published by permission of the Clhief Scientist, Australian Defence Scientific Service, Department of Supply, hZelboiirne, Victoria, Australia.
