V O L U M E 19, NO. 4, A P R I L 1 9 4 7 Table V. 3ample Yo.
1 2 3 4
5 6
7 8
9 10
241
Comparison of Chemical and Spectrographic Analyses for Sodium Chemical
0.150 0.185 0.185 0.205 0.260 0.290 0.300 0.340 0.390 0.415
Per Cent Sodium SpectroaraDhic -High Range
0.145 0.175 0.185 0.205 0.250 0.260 0.305 0.330 0.395 0.415
Deviation
0.005 0.010 0.000
3.3 5.4 0.0 0.0 3.9 10.3 1.7 2.9 1.3 0.0 ~2.9
0.000 0.010
0.030 0.005 0,010 0.005 0.000 Av. * 0 . 0 0 8
0.044 0.110 0.110 0.059 0.052 0.066
Low Range 0.044 0.108 0.112 0.055-
0.056 0,064 Av.
c.;.
Deviation
0.000 0.002 0.002 0.004 0.004 0.002 +=0.0023
0.0 1.8 1.8 7.3 7.1 3.1 *3.5
Table VI. Polarographic and Spectrographic Analyses for Vanadium Catalyst Per Cent Vanadium s a m p l e Polarographio Spectrographic 1 0.021 0.021 2 0.026 0.026
3 4 5
0.035 0.046 0.066
0.036 0.048 0.066
Av.
07 /G
Deviation
0.000 0.000 0.001 0.002 0.000 *0.0006,
Deviation
0.0 0.0
2.9 4.2 0.0 ~ 1 . 4
A1 3066.2, corrected for background intensity and the aluminum content of the sample or standard in question. The latter correction was made by multiplying the intensity ratio by %Al/5.73, 6.73% being the %A1 in most of the standards. This method was found t o give reliable results for catalysts of alumina contents varying over the range shown in Table I. The working curve is presented in Figure 4. DISCUSSION OF RESULTS
Comparisons of chemical and spectrographic determinations of the iron and sodium contents of a number of catalysts are given in Tables IV and V.
Table VII. Duplicate Spectrographic Analyses for Chromium, Nickel, and Copper Catalyst Sample 1
Chromium, % 0.0057,O. 0065
2
0.0019,0.0021
3 4
0.0058,O. 0062 0.0048,O. 0052 0.0074,O. 0069
5
Nickel, % 0.0053,O. 0060 0.0041,0.0040 0.0035,0.0038 0.0017,O. 0018 0.0070,O. 0071
Copper. %
0.0032,O. 0030 0.0010,0.0008 0.0012,O. 0012 0.0020,O. 0021 0.0010,0.0012
A similar comparison of polarographic and spectrographic results for vanadium is shown in Table VI. The analyses shown are for catalysts of similar aluminum content, the A1 2568 line being used as internal standard. Use of the silica internal standard gave similar values but poorer precision. Since suitable chemical methods for the determination of nickel, chromium, and copper in the concentrations and matrices in which they occur in catalysts were not in use in these laboratories, comparative analyses cannot be given for these metals. However, Table VI1 indicates the precision obtainable. About 30 minutes are required for the complete analysis when the sodium content of the catalyst is greater than 0.1%. Another 15 minutes may be added for catalysts of low sodium content because of the additional arcing necessary in such cases. ACKNOWLEDGMENT
The authors wish to express their indebtedness to B. E. Gordon who performed the polarographic analyses and t o Mrs. K. B. Woods who performed many of the spectrographic analyses. LITERATURE CITED (1) Hasler, M. F., and Dietert, H. W., J . Optical Soc. Am., 33, 218-28 (1943). (2) Hasler, M.F., and Harvey, C. E., IND. ENCI. CHEM.,ANAL.ED., 13, 540-4 (1941). (3) Hasler. 31. F., and Kemp, J. W., J . Optical SOC.Am., 34, 21-32 (1944). (4) Hasler, 51. F., and Lindhurst, R. W., Metal PTogress, 30, 50-63 (1938) (5) Page, J. E., and Robinson, F. A., Anakist, 68, 269 (1943).
(6) Pierce, JV C., and Nachtrieb, N. H., IND. ENCI.CKEiv.,
*~NAL.
ED., 13 774-81 (1941). (7) Post, C. B , Schoffstall. D. G., and Hurley. G., Ibid., 17, 412-16 (1945). (8) Saywell, L G . ,and Cunningham, B. B., Ibid., 9, 67 (1937).
Determination of Water in Phenol LOUIS R. POLL4CK, Industrial Laboratory, Mare Island .Vasal Shipyard, Vallejo, Calif.
Water in phenol is determined cryoscopically. The freezing point is determined before and after dehydration by boiling, and the percentage of w-ateris calculated as a linear function of the freezing point lowering. Satisfactory accuracy is ohtained up to 29'0 water, even in the presence of 1.1% rresol.
I
N T H E examination of phenol samples a t this laboratory, it
was considered advantageous to determine the water content. A desirable method should be rapid and simple, even when determinations are made infrequently. The literature revealed no adequate method urhich met these requirements. Fischer ( 1 ) proposed a specific volumetric method which has been thoroughly studied (6) and used by many investigators. However, infrequency of determinations would necessitate a restandardization against freshly prepared standards each time the reagent was used. This disadvantage appeared great enough to eliminate the method from further consideration.
Standard methods, such aa vacuum drying, heating a t 105O C., or drying over sulfuric acid or phosphorus pentoxide, yield erroneous results because of the volatility of phenol. Jones, Prahl, and Taylor ( 4 ) discussed the possibility of determining water in impure resorcinol by the difference in crystallizing points before and after drying. They were unable to dry their samples without changing the composition and so failed in their attempt, although they obtained a straight line when plotting crystallizing point against added water. The ease with which phenol may be dried by boiling makes a cryoscopic method entirely feasible, especially in view of the low
ANALYTICAL CHEMISTRY
242
molecular weight of water. The cryoscopic constant of phenol ( 3 ) ,7.2 to 7.5, gives a calculated lowering of the freezing point of 4.0 to 4.2" C. for each gram of water per 100 grams of phenol. Data reported by Leroux ( 5 )plot as a curve which closely approximates the straight line 45" = 4.0 (% water). The author's data support the equation AT = 3.7 (% water). The proposed method is applicable to the determination of small amounts of water in either pure or technical phenol. PROCEDURE
Approximately 25 grams of phenol are introduced into a 1 X 6 inch test tube and heated until completely melted. An accurate thermometer, graduated a t intervals of 0.1 O or 0.2" C., and a loop stirrer are inserted into the tube through a cork stopper. The freezing point tube is then suspended in an empty 500-ml Erlenmeyer flask by means of a cork stopper. The phenol is stirred a t a constant rate of 120 cycles per minute. When crystallization occurs, the temperature rapidly rises to a steady value which is recorded as the freezing point. A fresh 25-gram sample is placed in a 125-ml. Erlenme er flask and boiled until the refluxing vapors reach the top of tEe flask, and then for 1 minute longer. The contents of the flask are immediately protected with a soda-lime tube; and after cooling somewhat, the drying tube is removed and the sample poured into a 1 X 6 inch tube. The freezing point is determined a$ above. The percentage of water is calculated as follows:
% water where TI = freezing point, 1'2 = freezing point. -
~
_
.
Feezing Point Data
Freezing Point, ' C . Original Wet Dry 40.55 , ., 40.80 40.55 . . . 40.80
+
Error, Gram Water, Grams per 100 of Water per Grams of Phenol 100 Grams Added Calrd Detd. of Phenol .. 0.07 0.00 .. 0.07 0.00 0.10 0.10
0.10 0.10
0.11 0.11
tO.O1
0.24 0.24
0.31 0 31
0.30 0.30
-0.01
4 0 . 5 5 3 8 . 8 0 40.80 40.55 38.80 4 0 . 8 0
0.47 0.47
0.54 0.54
0.54 0.54
0.00
4 0 . 5 5 3 7 . 2 0 40.80 40.55 3 7 . 2 0 4 0 . 8 0
0.90 0.90
0.97 0.97
0.97 0.97
0.00
40.55 33.30 40.80 40.55 3 3 . 3 0 4 0 . 8 0
2.03 2.03
2.10 2.10
2.03 2:03
.., ...
40.30 40.30
0.00 0.00
,.
,.
0.22 0.22
40 30 40.30
0.23 0 23
0 45 0.45
0.45 0.45
0.00
39 50 37.80 40 30 39.50 37.80 40.30
0.45 0.45
0.67 0.67
0.68 0.68
+0.01
3 9 . 5 0 3 6 . 3 0 40.30 39.50 3 6 . 3 0 40.30
0.88 0.88
1.10 1.10
1.08 1.08
-0.02
3 9 . 5 0 3 2 . 4 5 40.30 3 9 . 5 0 3 2 . 4 5 40.30
2.02 2.02
2.24 2.24
2.12 2.12
-0.12
40.55 39.7@ 40.80 40.55 39.70 4 0 . 8 0
39.50 39.50
39.50 38.65 3 9 . 5 0 38.65
Figure 1.
Effect of Water upon Freezing Point
111order to determine the effect of impurities on the accuracy of the method, the most probable impurity, cresol, was added in fairly high percentage. Table I shows the results obtained. DISCUSSION
C., before drying C., after drying
4 0 . 8 0 4 0 . 4 0 40.80 4 0 . 8 0 40.40 40.80
Phenol 1.1% cresol
(T2 - T I )
-
.._
Table I.
Sample Phenol
= 0.27
Grams of Water per 100 Grams of Phenol
-0
07
....
Completeness of dehydration is indicated by both the constancy wid actual value of the freezing point after boiling. The dry freezing point is only 0.1 C. lower than the accepted value (a), a not unreasonable difference for a C.P. grade reagent which w a ~ not further purified. The equation, yowater = 0.27 (Ti- T I ) ,was derived from the straight line (Figure 1) obtained by plotting the freezing point data. .-\lthough the equation actually gives grams of water per 100 grams of phenol, the error introduced by calling this valiie percentage is negligible in the applicable region. The accuracy is not lowered in the presence of cresol, the most conimon impurity. Highly volatile constituents other thari water would interfere, but the effect decreases with increasiiig molerular weight. Practjcally, this id not a serious objecti~iii. as such materials are not normally present in phenol. Reproducibility is good. Duplicate determinations made o n the same batch of prepared sample yield identical results. AIthough the errors may be such as to give a rather large relative error a t very low water concentrations, the absolute errors wmain low up to lTc water. The accuracy is usually at or withiri the limit to which temperature readings can be made. This i> more clearly illustrated by the small deviations of the experimental points from a linear curve (Figure 1). The accuracy fall$ off rapidly, the error increasing to the order of 0.1% water at a concentration of 2%. Thus, 2 5 of water would appear to he about the upper limit a t which the method will yield result* of satisfartory accuracy. ACKNOWLEDGMENT
The author is indebted to K. E. Bsaver and H. G. Isbell of laboratory, who critically read the manuscript.
tiii-
RESULTS
Difficulty was encountered in an attempt to prepare standard samples by adding veighed amounts of water to dry phenol. The method finally adopted consisted of first determining the water in C.P. grade phenol by the author's method and making subsequent weighed additions. The total water was then calculated as the sum of the added water and the uater already present. Temperature readings were made to the nearest 0.05" C. on a thermometer which was graduated at intervals of 0.1" C . and calibrated at 32.38" C., the melting point of sodium sulfate dwahvcirn t P
LITERATURE CITED (1) Fischer, K., A n g e w . Chem., 48, 394 (1935). (2) Intern. Crit. Tables, Val. IV. p. 15 (1928). (3) Ibid., p. 183.
(4) Jones, D. O., Prahl, M. A . , and Taylor, J. R., IND.ENQ.CHEM.. ANAL.ED.,4, 84 (1932). ( 5 ) Leroux, H., J . pharm. chim., 20, 88 (1919). (6) Smith, D. M., Bryant, W '. M , D., and Mitchell, J., Jr., J . d m Chem. SOC.,61, 2407 (1939). THLviews expressed by the author are hip own a n d do not necessarily reflect the opinion- nf the Navy Department.
