950
ANALYTICAL CHEMISTRY
Theoretical results were obtained, thus confirming on a micro scale the observations of Willits and co-workers. Although these authors and others have reported blanks due to alkali entrainment (and considerably reduced them with a new connecting bulb), this is not a problem in micro-Kjeldahls, using either a Kirk or a Parnas and Wagner apparatus (6). The third modification consists of a simplified titration procedure. The use of boric acid as a receiver in micro-, semimicro-, and macro-Kjeldahl procedutes is widespread. Ordinarily, standard hydrochloric or sulfuric acid is used to titrate the trapped ammonia. Niederl (6) uses 0.01 N potassium biiodate as a receiving solution, and back-titrates with standard alkali. In this laboratory, the advantages of boric acid and potassium biiodate are combined. Because potassium biiodate is a primary standard as well as a strong stable acid, the use of a base either for titration or standardization is eliminated. The receiving liquid is 2% boric acid, to which has been added sufficient bromocresol green-methyl red mixed indicator (3)to give a faint pink color when 5 ml. of this solution are diluted to 17 ml. with distilled water. Five milliliters of this solution are pipetted into a test tube, and the distillation is carried out as
described above. Titration is carried out with 0.01 N potassium biiodate solution ( 4 ) to an end point determined by comparison with the boric acid-indicator solution (5 ml. diluted to 17 ml.). ACKNOWLEDGMENT
The authors are indebted to Catharine M. Brown for the analyses involved in developing these modifications. LITERATURE CITED
Goessman, C. I., Mass. Agr. Expt. Sta., Bull. 54 (1898). (2) Kirk, P. L., IND.ENG.CHEM.,ANAL.ED.,8, 223 (1936). (3) Kolthoff, I. M., and Sandell, E. B., “Textbook of Quantitative Inorganic Analysis,” p. 451, New York, Macmillan Co., 1946. (4) Niederl, J. B., and Niederl, V., “Micromethods of Quantitative Analysis,” 2nd ed., p. 54, New York, John Wiley & Sons, 1942. ( 5 ) Ibid., p . 73. (6) Parnas, J. K., and Wagner, R., Biochem. Z.,125, 253 (1931). (7) Poszi-Escot, M. E., Bull. soc. chim., 31, 932 (1904). (8) Willits, C. O., John, H. J., and Ross, L. R., J . Assoc. Ofic. Apr. Chemists, 31, 432 (1948). (1)
RECEIVED June 27. 1949.
Optical-Crystallographic Identification of Sulfanilamide BRIGGS J. WHITE, NORMAN F. WI’IT, JOHN A. BILES, AND CHARLES F. POE University of Colorado, Boulder, C o b .
ANY of the chemical tests for sulfanilamide have not been specific. As an extension of similar studies in this laboratory (9, 6, 8, Q), an optical study of several derivatives of sulfanilamide was undertaken, in order to facilitate the identification of this compound. PREPARATION AND ANALYSIS
The Schiff bases were prepared by the reaction of equimolecular amounts of sulfanilamide and aldehyde in ethyl alcohol, the mixture being warmed for about 5 minutes to ensure complete reaction ( 2 ) . The product was then removed by filtration and crystallized usually from alcohol. The crystals &ere washed with either acetone or alcohol, depending on their solubility. Several compounds were prepared which did not form crystals of sufficient size to be of use in the determination of their optical-crystallographic properties. Except for a description of the crystal appearance of the Schiff bases from benzaldehyde and cinnamic aldehyde (15),no optical data are found in the literature. Several of the sulfanilamide-cinchona addition compounds &ere prepared, following the methods described in the literature (10). Anils with sugars also were prepared by the method described in the literature (8). The melting points of the purified compounds were determined on a “bloc-Maquenne” apparatus. No stem correction was made. Nitro en was determined by the Gunning method ( 1 ) . Concentrated aydrogen peroxide solution was used to hasten the decomposition of some of the compounds according to the method proposed in this laboratory (7). The optical-crystallographic properties of the com ounds were obtained by the use of a petrographic microscope. Tge refractive indexes were determined by the immersion method; the interference figures were used as a means of determining the optical orientation of the crystals. The most usual orientations are noted, in order to facilitate the use of the optical pro erties in the detection of sulfanilamide. The temperature a t whicx the indexes were determined was 25’ 1 C. O
EXPERIMENTAL RESULTS
The data obtained are peported in Table I. Guided by them a method of identification based on the optical-crystallographic properties of p-chlorobenzylidene sulfanilamide has been devised. To a small amount of the unknown on a microsco e slide, a drop of water and a drop of a saturated solution of phorobenzalde-
hyde are added. The slide is warmed gently over a small flame. After crystals have formed, the excess water is removed by a microfilter, and the crystals are dried carefully over a small microflame. The crystals are mounted in liquids having indexes of refraction of 1.655 and 1.703. The former index corresponds to the index beta. The crystals will have a higher index of refraction than 1.703 in one position of extinction. An alternative procedure is suggested, in order to obtain c stals that are large enough for optical-crystallographic study, wyen the concentration of the sulfanilamide is low. One of the cinchona alkaloid addition compounds is used in this test. Five milliliters of an alcohol or water solution of the substance, which is thought to be sulfanilamide, are placed in a small beaker, and t o this are added a few milliliters of a dilute solution of uinine bisulfate. The solution is heated slowly until there is o a y a small volume, and then i t is cooled for 15 minutes below room temperature. A small portion of the crystals is transferred to a glass slide. The crystals are washed with alcohol and then with acetone; the excess liquid is removed in each instance. The crystals are air-dried and warmed slightly to make certain that they are completely dry. Two slides of the crystals are prepared, one set of crystals mounted in an immersion liquid of refractive index 1.657 and the other set mounted in one of refractive index 1.668. The crystals become invisible in each immersion liquid at the correct position of extinction. Large crystals are obtained which give characteristic acute bisectrix interference figures. The other optical properties, which are listed for this compound in Table I, also may be determined. If additional confirmation is desired, other derivatives given in the table may be prepared and tested in a similar manner. POLYMORPHISM OF SULFANILAMIDE
-4ttempts were made to isolate different crystalline phases of sulfanilamide. Three phases were found and are described.
A. Sulfanilamide Monohydrate. Sulfanilamide monohydrate was obtained by the method described by Kienle and Sayward (6) by letting a cold (20’ C.) saturated solution of sulfanilamide crystallize in a refrigerator a t 4 ” C. Transformation to anhydrous sulfanilamide is rapid a t 25” C., especially if the humidity is not high. System, orthorhombio Sign, positive Common orientation, Bxa Elongation, plus or minus
V O L U M E 2 2 , N O . 7, J U L Y 1950 Table I.
Analytical a n d Crystallographic D a t a of Sulfanilamide Derivatives
Compound Benzvlidene sulfanilamide o-Chiorobenzylidene sulfanilamide p-Chlorobenzylidene Sulfanilamide Cinnamvlidene sulfanilamide 3.4-Dimbthoxybenzylidene sulfanilanude 2.4-Dimethoxybenzylidene sulfanilaniiiie Furfurylidene sulfanilamide o-Hydroxybenzylidene sulfanilamide p-Hydroxybenzylidene sulfanilamide p-Methoxybenzylidene sulfanilamide m-Methylbenzylidene sulfanilamide o-Nitrobsnzylidene sulfanilamide m-Nitrobenzvlidene sulfanilamide p-Sitrobenz;lidene s~dfanilamide Cinchonidine sulfanilamide HzSO, Quinine sulfanilamide HrSO, Quinine sulfanilamide l’/z HtSO’ Glucoseanil sulfanilamide Mannoseanil sulfanilamide a ¶ ,
b
951
Melting Point Block,
Nitrogen Calcd., Found,
%
O C .
188 180 186 216 193 19’7. 196 211 204 200 201 183 170 175 183 209 186 211 202
10.16 9.02 9.52 9.79 8.75 8.75 11.20 10.14 10.14 9.66 10.22 13.77 13.77 13.77 8.80 8.41 8.71 8.38 8.38
%
10.73,10.70 9.68, 9.60 9.52, 9.46 9.68, 9.64 8.85, 8.71 8.72, 8.80 11.12,11.07 10.07,10.02 10.20,10.25 9.69, 9.80 10.05,10.11 13.77.13.65 13.73,13.68 13.79,13.75 8.75, 8.67 8.40, 8.35 8.84, 8.86 8.28, 8.20 8.22. 8.28
Opti- ElonSign
ga-
tion
Refractive Indexes a t 25 %_ Alpha Beta Gamma 1.494 1.676 >1.703 > 1.703‘ 1.514 >1.703 1.655 >1.703 1.486 > 1.703” >1.703 1.528 1.521 1.605 > 1.703 1.674 > I 703 1.655 > 1.703 1.651 1.493 > I .703 1.680 1.482 >1.703 1.666 1.512 1.645 >1.703 1.498 1 661 1,492 >1.703 1.690 21 703 1.476 1 676 1,574 > 1 . 70x >1.703n 21.70: 1.524 1 5Y.i > 1 b71h 1.507 1,657 1.596 1.668 1.618 1.574 >1.703 1 569 1 574 >1.6766 1.581 1 615 1 636
Axial Disper-
sion r > v r > u r > c
Sone
v > r
r>r r > o
None Sone r > u None None None hione None r 2 v None r > u r > 7,
Crystal System Monoclinic AM~noclinic Monoclinic Monoclinic Monoclinic Monoclinic hlonoclinic Monoclinic Monoclinic Monoclinic i\tonociinic Orthorhombic Orthorhombic Orthorhombic hfonoclinic Monoclinic Monoclinic Monoclinic Monoclinic
is only a small amount above 1.703.
Crystals dissolve in oil above recorded refractive index.
No dispersion No pleochroism Alpha, 1.505 Beta, 1.639 Gamma, >1.85
B. Anhydrous Monoclinic Phase. This stable phase, as Watanabe (19)found, predominates in commercial preparations. Most desirable crystals for microscopic studies were obtained by hastening crystallization from hot acetone solution. These crystals appear to be orthorhombic between crossed Nicols, but are definitely monoclinic. The same phase, but different habit, was obtained from methanol. Crystals from the latter solution do not appear orthorhombic. Goniometric measurements and refractive indexes proved, as pointed out by Watanabe, that the crystals from acetone and methanol were the same phase. System, monoclinic Sign, positive Common orientation, E t a Elongation, negative Dispersion axial, slight, c > r No pleochroism Alpha, 1.555 Beta, 1.672 Gamma, > 1.85 Keenan ( 4 ) reports for this phase the following: System, ? Alpha, 1.570 Beta (ni), 1.677 Gamma, > 1.733 C. Anhydrous Monoclinic Phase. This stable phase is obtained upon crystallization from hot n-propyl or n-butyl alcohol, from chloroform, or from water on long standing. No transformation of phase C was evident after one year’s standing. System, monoclinic Sign, positive No dispersion KO pleochroism Common orientation, centered E t a Elongation, positive ( E t a ) Alpha, 1.547 Beta, 1.633 Gamma, >1.85 The data for this phase correspond to those found in this laboratory by White (IS). Van Zyp (11) reported different habits of sulfanilamide which he considered to be the same phase. Watanabe (12)reported x-ray and goniometric studies of three phases. Williams and Maresh (14) reported no quantitative data or optical-crystallographic propert,ies in isolating five phases of sulfanilamide By using ten different organic solvents and water, two anhydroua phases of sulfanilamide and the monohydrate were isolated. A complete correlation between the results obtained in this
laboratory and the results reported by Watanabe, Van Zyp, and Williams and Maresh was not possible. SUMMARY
Fourteen Schiff bases, three cinchona alkaloid addition products, and two anils with sugars of the sulfanilamide have been prepared and analyzed, and their optical-crystallographic properties have been reported. Sulfanilamide has been recrystallized from different solvents and analyzed, and the optical-crystallographic properties have been reported for three distinct phases. &4method of identification of sulfanilamide making use of the optical-crystallographic data of the Schiff base with p-chlorobenzaldehyde and the quinine bisulfate addition product has been suggested. LITERATURE CITED
(1) Assoc. Official Agr. Chemists, “Official and Tentative Methods of Analysis,” 3rd ed., 1930. (2) Gray, W. H., Buttle, G. A. H., and Stephenson, D., Biochem. J . 31,724(1937). (3)Hultquist, M. E.,Poe, C. F., and Witt, K . F., J . .4m. Chem. Soc., 67,588 (1945). (4) Keenan, G. L.,J. Assoc. Ofic.Agr. Chemists, 27, 153 (1944). (5) Kienle, R. H., and Sayward, J. M., J . Am. Chem. SOC.,64,2464 (1942). (6) Larsen, Junius, Witt, N. F., and Poe, C. F., Mikrochemie, 34,1 (1948). (7) Poe, C. F., and Dewey, B. T., J . Am. Pharm. Assoc., 25, 419 (1936). (8) Poe, C. F.,and Sellers, J. E., J . Am. Chem. SOC.,54,249 (1932). (9)Poe, C. F.,and Swisher, C. A.,Zbid., 57,748 (1935). Powell, H. )VI,, Rose, C. L.,and Bibbina, F. E., J. (10) Stuart, E.H., Am. Pharm. Assoc., 28, 90 (1939). . 75,585 (1938). (11) Van Zyp, C., P h a ~ m Weekblad, (12)Watanabe, A,, Naturwissenschaften, 29, 116 (1941). (13)White, B. J., Univ. Colo. Studies, 26,104 (1941). (14)Williams, E. F.,and Maresh, C., Abstracts of Papers, 104th Meeting, AM.CHEM.SOC.,Buffalo, N.Y., Sept. 7 to 11, 1942, p. 2L. (15) Yalowitz, M.L., J . Assoc. Ofic. AUT.Chemists, 21, 351 (1938). RECEIVEDAugust 15, 1949.
Correction In the article on ‘(Stable High-Frequency Oscillator-Type Titrimeter” [Anderson, Kermit, Bettis, E. s.,and Revinson, David, ANAL.CHEM., 22,743 (1950)], the professional connection of the authors should have been given as Fairchild Engine and Airplane Corporation, K’EPA Division, Oak Ridge, Tenn.
