ANALYTICAL CHEMISTRY
310 Table V. Nitro Nitrogen in Commercial Diazodinitrophenol by Titanous Chloride Titration Method Specimen A
Specimen B
Specimen C
%
%
70
13.04
12.99
13.04
13.01 13.00
13.00 13.01 13.01
Av. 13.04
Specimen
D %
Specimen
12.97 12.92 12.95
E
% 13.08 13.10 13.09
Specimen
F %
13.07
...
13.07
Using this method, purified diazodinitrophenol was found in two experiments to contain 13.33 and 13.33%, respectively, of nitro nitrogen, the theoretical amount. Similarly, six specimens of commercial diazodinitrophenol were analyzed for nitro nitrogen with the results recorded in Table V. By deducting the results in this table from the corresponding ones in Table IV, the amount of amino nitrogen can be found. These results, although not highly accurate, were the best that could be obtained. ACCURACY AND PRECISIOfi
The nitrogen evolution method for the measurement of diazo nitrogen appears to be accurate to within 0.5%. The standard deviation from the average of the seven results in Table I, expressed as per cent diazo nitrogen, is 0.05. The results for nitro (and amino) nitrogen found by the modified Simek method (Table
IV) show a somewhat higher accuracy and a standard deviation of 0.04. The titanous chloride volumetric method is accurate within 0.3%. The results by the latter method, expressed as per cent nitro nitrogen (Table V), show a standard deviation of only 0.014. LITER4TURE CITED
(1) Becker, W.W., IND.ENG.CHEY.,ANAL.ED.,5, 152 (1933). (2) Clark, L. V., I n d . Eng. Chem., 25, 663 (1933).
(3) Gattermann, L., “Practical Methods of Organic Chemistry”, pp. 396-401, tr. by Schober and Babasinian, 3rd rlmerican translation from 11th German ed., New York, Macmillan Co., 1917. (4) Grandrnougin,E., Ber., 40,422 (1907). (5) Houben, J., “Methoden der organischen Chemie”, 3rd ed., Vol. IV, p . 878, Ann Arbor, Edwards Brothers, 1944. (6) Klemenc, A , , Ber., 47, 1414 (1914). (7) Knecht and Hibbert, “New Reduction Methods in Volumetric Analysis”, p. 33, New York, Longrnans, Green & Co., 1925. (8) Koenigs, W., Ber., 10,1531 (1877). (9) Mehner, J . prakt. Chem., (2), 63, 305 (1901). (IO) Meyer, Hans, “Analyse und Konstitutionermittlung organischer Verbindungen”, p. 716, 6th ed., Vienna, Julius Springer, 1938. (11) Pierce, A. E., and Rising, &I. M.,J . Am. Chem. Soc., 58, 1363 (1936). (12) Rathsburg, H., Ber., 54, 3183 (1921). (13) Schmidt, J., and Maier, W., Ibid., 64, 778 (1931). (14) Schmidt, O., Ibid., 39,614 (1906). (15) Simek, B. G., Chem. Listy, 25,322-5 (1931). (16) Wienhaus, H.. and Ziehl, H., Ber., 65, 1461 (1932).
Test for tert-Butyl and Isopropyl Alcohols with RICHARD F. ROBEY AND NAT C. ROBERTSON Esso Laboratories, Standard Oil Development Company, Elizabeth, .V. J . The scope and some interferences in the mercuric sulfate method for the detection of impurities in commercial isopropyl alcohol and for the identification of isopropyl alcohol have been investigated and are clarified.
T
H E reaction of tert-butyl alcohol with an acid solution of mercuric sulfate to give a yellow precipitate was first reported by Denighs (2); and for some time has been employed to detect tert-butyl in commercial isopropyl alcohol ( 1 , 5 ) . Pure isopropyl alcohol gives a white precipitate on warming with the reagent. The yellow color imparted to the test mixture by small concentrations of tert-butyl alcohol may be matched with a set of standards to provide a method of quantitative estimation. A report by Marks and Lipkin (4) that diisopropyl ether, another possible contaminant of commercial isopropyl alcohol, also gives a yellow precipitate with the reagent, however, casts some doubt on the specificity of the test. Isobutylene is also known to give a positive response, and it seemed that other tertiary olefins might interfere. A brief investigation has revealed that the yellow coloration is not obtained with the small concentrations of diisopropyl ether and the tertiary olefinic propylene polymers which might possibly be present in commercial refined isopropyl alcohol from olefin hydration processes. On the other hand, very minute amounts of oxygenated isobutenyl derivatives, such as mesityl oxide and phorone, do produce a yellow coloration. It is concluded that the appearance ot a yellow precipitate is a sensitive semiquantitative test for impurities in isopropyl alcohol, but that the identity of the impurity or impurities is not made certain by this test alone. A white precipitate obtained under the milder set of test
conditions outlined herein, in conjunction with infinite miscibility of the sample with water, is a fairly reliable means of identifying isopropyl alcohol or its aqueous solutions. The precipitate may be tinted various shades of yellow, depending on the concentration and type of impurities accompanying the alcohol. EXPERIMENTAL
I n this work the following composition of mercuric sulfate reagent and proportions were found to result in outstanding sensitivity : The reagent was prepared by dissolving 50 grams of yellow mercuric oxide in 200 ml. of concentrated C.P. sulfuric acid, adding this solution to 600 ml. of distilled water, and diluting to 1 liter, also with distilled water. I n carrying out the test 1.0 ml. of the reagent was mixed with 1.0 ml. of distilled water in a test tube, and 2.0 ml. of the substance being tested were added. The mixture was then heated in a water bath and the character and color of the precipitate, if any formed, mere noted. The effect of temperature and duration of heating on the results of the test are discussed below. With the exception of a laboratory preparation of tertbutyl isopropyl ether, and the Standard Alcohol Co.’s (now the Enjay Co., Inc., New York, Ii.Y.) isopropyl alcohol, ethyl alcohol, methyl ethyl ketone, diisobutylene, and isopropyl ether, the substances tested were purchased from the Eastman Kodak Co. The compounds immiscible with water were repeatedly extracted with water to remove any tert-butyl alcohol present. The others were of chemically pure quality.
V O L U M E 19, N.O. 5, M A Y 1 9 4 7 The tert-butyl isopropyl ether was prepared from tert-butyl and isopropyl alcohols by a method devised by Gilliland ( 3 ) . An aqueous alcoholic azeotrope boiling a t 70-71" C. and containing 20 to 3oY0 of the ether was taken overhead. This was washed four times with 30% sulfuric acid and eight times with water to remove alcohols. The ether was dried over calcium sulfate, refluxed 2 hours over sodium, and distilled through a packed column (boiling point = 87.6'). DISCCSSIOh OF RESULTS
The test Jvas first applied to a number of organic compounds in undiluted form to test the specificity of the reagent for identifying isopropyl and tert-butyl alcohols. Although earlier published test methods usually have specified only "gentle warming" of the test mixture, it developed that certain substances-e.g., isopropyl alcohol-would give precipitates \Then heated a t 75' C. for less than 5 minutes, while others such as ethyl alcohol would not respond under these conditions but would give precipitates a t a higher temperature of about 100" and in periods up to 10 minute- In 'Table I the compounds are classified according to
311 Table I.
Reaction of Various Substances to Mercuric Sulfate Test Reagent
Characrer or s o . of Substance Quantity of P p t . Color Layers I. Substances giving precipitate within 5 minutes a t 75' C. Isopropyl alcohol (87%) Moderate White 1 Heavy Bright yellow4 1 tert-Butyl alcohol sec-Butyl alcohol Light Bright yellow 2 Light D a r k yellow 2 Diisopropyl ether Lfoderate Grayish 2 Phorone Light Orange 2 Isophorone tert-Butyl chloride Heavy Bright yellow 2 Heavy Bright yellow 2 tert-Butyl isopropyl ether Heavy D a r k yellow 2 Polymer oil (plant) 11. Substances giving precipitate n i t h i n 10 minutes a t 100' C. Light White 1 E t h y l alcohol (95%) Mesityl oxide Light G r a y needles 2 Light Bright yellow 2 n-Butyl alcohol 111. N o precipitate under either set of conditions Acetone ..... ......... 1 Methyl ethyl ketone ..... ......... 2 Diacetone alcohol ..... ......... 2b Diisobutylene ..... ......... 2 Formed heavy precipitate a f t e r few seconds of slight warming. b One layer initially b u t two layers formed with heating.
their response to the milder and the more severe test conditions, and the quantity and color of precipitates are noted. The polymer oil included in the table is a predominantly unsaturated hydrocarbon material formed as a common by-product from the polymerizing action of sulfuric acid in the commercial process of manufacture of isopropyl alcohol from propylene. It generally contains several per cent of combined oxygen. Most of those substances that gave colored precipitates in undiluted form imparted a distinctly yellow color t o the precipitate formed when diluted to 1% or lovier concentration with purest commercial iqopropyl alcohol. Phorone and mesityl oxide, which gave grayish precipitates when tested in undiluted form, also gave a yellow precipitate when in minute concentrations in isopropyl alcohol. Dilute solutions of a number of substances in 87 weight yo aqueous isopropyl alcohol nere prepared and tested a t 75' for 5 minutes. The intensity of color observed a t several concentrations was matched by direct visual comparison with that given by six standard solutions of tert-butyl alcohols of 0.01, 0.02, 0.04, 0.06, 0.08, and 0.10 volume Yo concentration in purest isopropyl alcohol. (P.V. Smith of this laboratory has recently found that aldehydes prevent the normal action of the reagent.) This concentration range was chosen as the one in which differences in color of the precipitate are most easily detectable. Figure 1 is a semilogarithmic plot of the concentration of eight substances in isopropyl alcohol ss, ordinate against an abscissa denoting the concentration of tert-butyl alcohol which gives an equal colorimetric response to the test. It is apparent that mesityl oxide, phorone, tert-butyl isopropyl ether, and tert-butyl chloride give strongly positive tests a t much lower concentration than that of tert butyl alcohol required for an equivalent response. Decidedly higher concentrations of polymer, isophorone, and isopropyl ether are required, in fact much higher than would be expected in commercial refined isopropyl alcohol. These data show that care must be taken in interpreting results of the test for tert-butyl alcohol in isopropyl alcohol using DenigBs reagent. Other chemical and physical methods must be employed t o eliminate the possibility of interference. Conversely, if the presence of one of these substances is established, the scope of the test may be broadened to permit an estimation of its concentration in the absence of the others. LITERATURE CITED EQUIVALENT CONCENTRATION OF TERT.- BUTYL ALCOHOL, VOLUME %
'Figure 1. Concentrations of Compounds in Iso'propyl Alcohol Required to Give Same Colorimetric Response to DenigAs Reagent as Concenrtrations of tert-Butyl Alcohol Given on Abscissa
(1) Buc, U.S. Patent 1,911,798 (1933). (2) DenigBs, Compt. rend,, 126, 1145, 1277 (1898). (3) Gilliland, U. S. Patent 2,160,854 (1939). (4) Marks and Lipkin, J. Org. Chem.. 3, 598 (1939). (5) Pukirev, J. Applied Chem. (U.S.S.R.), 8, 1309 (1935).
