were corrected to p H 7.2 proportionally t o the changes in Q with p H (Equation 4). The T / W values thus calculated increased linearly with the nitrogen content. Another requirement for the applicability of this method is that the sohtions should follow Beer’s law at a given pH. Separate experiments showed that the color produced was proportional to concentration for a given material and PH. From the practical point of view, the stability of the solutions for colorimetry is of great importance. The color intensity of solutions in the PH range 7 t o 7.5 increases by 1 to 2% during the first 3 t o 4 hours after preparation and is subsequently unchanged. For solutions above p H 8, the color intensity reaches a maximum about 6 hours after
preparation and decreases slowly afterwards, ACKNOWLEDGMENT
The authors are indebted t o T. E. Timell of the Pulp and Paper Research Institute of Canada for supplying samples I to I11 with the nitrogen determinations and to P. F. Davison for determining the nitrogen contents of samples IV and V. LITERATURE CITED
(1) Alexander, TV. J., Rlitchell, R. L., ANAL.CHEM.21, 1497 (1949). (2) Bennett, C. F., Timell, T. E., Svensk 73 (1966). (3)Papperstidn, Brooks, C.,” 1 Badger, R. &I., J . Am. Chem. sot. 72, 1705 (1950).
(4) International Critical Tables, Vol.
VI, p. 272, McGraw-Hill, New York, 1929. ( 5 ) Levy, M., Palmer, A. P., J. Biol. Chem. 136, 57 (1940). (6) Lindsley, C. H., Frank, M. B., Ind. Eng. Chem. 45, 2482 (1953). (7) Ling, E. R.1 Chem. c% Ind. (London) 61, 194 (1942). (8) Michaelis, L., G ~ +4.,~ ~i ~ 2. 109, 165 (1920). (9) Rassow, B., Schultsky, H., NitroceLhlose 2, 189 (1931). (10) Riiber, O., Norsk Skogind. 9 , 204 ( 1955). (11) Smith, T. H., Zbid., 8, 402 (1954). (12) Snell, F. D., Snell, C. T., “Colorimetric RIethods of Analysis,” Vol. I, p. 629, Van Nostrand, New York, 1936. (13) Timell, T. E., Purves, C. B., Svensk Papperstidn. 54, 303 (1951).
RECEIVEDfor review April 18, 1958. Accepted August 28, 1958. Contribution of the Organic Chemical and Byproduct Division, Industrial Cellulose Research, Ltd., Hawkesbury, Ont.
Titration of Sulfoxides in Acetic Anhydride DAVID C. WlMER Abbott laboratories, North Chicago, 111.
During investigation of the titration of various weak bases, dimethyl sulfoxide was found to exhibit sharp end point inflections in acetic anhydride. The procedure was applied to other sulfoxides with the purpose of developing a general analytical method, and reproducible results were obtained with aliphatic, aromatic, and heterocyclic sulfoxides. Sulfides and sulfones, in general, do not interfere with the method. Attempts to titrate mixtures of sulfoxides differentially were unsuccessful, indicating probable minor differences in actual base strength.
EXPERIMENTAL WORK
Table 1. Titration of Various Compounds in Acetic Anhydride Max. AE/AV, ~
Compound Bis(2-hydroxyethyl) sulfoxide Dibenzyl sulfoxide Diethoxy sulfoxide (diethyl sulfite) Dimethyl sulfoxide
T
present method is a n extension of work described earlier on the titration of amides in acetic anhydride (8). Following completion of this work on sulfoxides, Streuli (7) reported the successful titration of dimethyl sulfoxide in acetic anhydride. KO other compounds of this type were cited. Analytical attack on the sulfoxide group usually involves reduction methods using titanium trichloride (2, 4) or stannous chloride (3). Infrared techniques have been used to detect and determine sulfoxides, but the methods are not generally applicable ( I ) . Polarography appears t o offer little assistance as Stone (6) reports that sulfoxides are not reducible at the dropping mercury electrode. Combustion methods specifically designed for sulfoxides and sulfones have been described (9). HE
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ANALYTICAL CHEMISTRY
Diphenyl sulfoxide Di-p-tolyl sulfoxide p,p’-Dihydroxydiphenyl sulfoxide Phenothiazine 5-oxide Phenoxathin 10-oxide Thianthrene 10-oxide
Mv./Ml. (Ap% prox.) 96.9 120 96.9
Purity,
98.1 580 98.1 No titration curve inflection obtained 99.9 1030 99.8 99.0 130 99.4 98.8 370 98.4 55.0“
300
96.9 97.8 98,6 98.6 95.9 95.0 95.0 95.3 100.1
230 300 100
Thianthrene 5,lO100 dioxide Trimethylphosphine 1420 oxide Incompletely soluble in acetic anhydride. 0
Apparatus. A Precision-Dow Recordomatic Tit.rometer, Model K-3247, was used in all titrations. T h e modified calomel-glass electrodes used were described in a n earlier paper (8). Reagents. ACETIC ANHYDRIDE, ACS reagent grade. DIOXANE, purified by the procedure of Sideri and Os01 (6). PERCHLORIC ACID, 70% vacuum distilled. Available from the G. Frederick Smith Chemical Co., Columbus, Ohio. PERCHLORIC ACID TITRANT. A 0.1N solution is prepared by diluting 9 ml. of 70y0 perchloric acid to 1 liter with purified dioxane. The solution is allowed to stand 24 hours prior t o use. The titrant may be standardized either visually or potentiometrically against primary standard potassium acid phthalate dissolved in acetic acid.
Procedure and Results. An approximately 0.001-mole sample, accurately weighed, is dissolved in 7 5 ml. of acetic anhydride and titrated potentiometrically with freshly standardized 0.1S perchloric acid in dioxane. The end point may be determined by inspection or calculation of maximum U / A V . All samples were analyzed as received without further purification. The relative degree of basicity may be ascertained by inspection of the first derivative values listed in Table I. Attempts to resolve mixtures of sulfoxides by differential titration were
~~
h ~~
unsuccessful. Only single inflections were observed. This indicates the differences in the magnitude of maximum U / A V probably represent minor differences in actual base strength. DISCUSSION
Sulfides and sulfones, possible impurities in sulfoxides, in general exhibit no measurable b?sicity in acetic anhydride Tvhen titrated with perchloric acid. Trimethylphosphine oxide, though not a sulfoxide, has been included for
comparison as amine oxides have been found to exhibit very sharp inflections in acetic anhydride. Diethoxy sulfoxide (diethyl sulfite) could not be titrated as a base in acetic anhydride. The direct titration of sulfoxides in acetic anhydride offers a rapid and reproducible approach t o purity determination. The method appears t o be limited only by the solubility of the particular sulfoxide in acetic anhydride.
(2) Barnard,
D.,
Hargrave,
K.
R.,
Anal. Chim. Acta 5 , 536-45 (1951). (3) Glvm, E., Analust 72, 248-50 (1947).
(4) Lggault, R. R.; Groves, K., ‘AXAL. CHEM.29. 1495-6 (1957). (5) Sideri, C. N., Osoi, A., 3. Am. Pharm. ASSOC., Sci. Ed. 42, 586 (1953). (6) Stone, K. G., J . Am. Chem. SOC.69, 1832-3 (1947). (7) C. A., A 4 ~CHEW ~ ~ 30, . 997. 1000 -Streuli, (1958). ’ (8) Wimer, D. C., Zbid., 30, 77-80 (1958). (9) Young, G. H., IND. ENG. CHEM., ANAL.ED. 10, 686 (1938).
LITERATURE CITED
(I) Barnard, D., Fabian, J. ?*I.,Koch, H. P., J. Chem. SOC.1949, 2442-54.
RECEIVED for review May 12, 1958. Accepted July 16, 1958.
Determination of Reduced Titanium Chlorides in Fused Salt Melts SVANTE MELLGRENl and MARSHALL B. ALPERT Titanium Division, National lead Co., Sayreville, N. J. Two methods have been developed to determine titanium dichloride and trichloride dissolved in or mixed with alkali or alkaline earth chlorides. Both procedures require analysis for total soluble titanium by titration with ferric ammonium sulfate. In the first method the sample is reacted with dilute hydrochloric acid, the volume of hydrogen evolved being a measure of the titanium(l1) chloride present. In the second procedure the acid titratable with base under controlled conditions permits a determination of the apparent valence of the titanium.
P
electrodeposition of titanium metal from fused chloride melts in diaphragmed cells (3. 4),for the electrorefining of titanium metal (14) and of titanium(1V) chloride (j), and for titanizing base metals ( 1 ) directly employ melts containing the reduced titanium chlorides in solution in a mixture of one or more of the alkali or alkaline earth metal chlorides. Such melts are also encountered as intermediates in an electrolytic process for the preparation of titanium from titanium(1V) chloride in a diaphragmless cell ( 2 ) and in a chemical reduction process employing sodium as reductant for titaniurn(1V) chloride ( 1 1 ) . The total amount of titanium ion present and the relative amounts of titaniuni(I1) and (111) are important variables. A method was required to determine these amounts and also to determine equilibria between reduced titanium chlorides and titanium metal in fused salt systems (12). Because the 1 Present address, Amco Research, Inc., a Subsidiary of American Metal Climax, Inc., Carteret, N. J. ROCESSES FOR THE
pure compounds are reactive toward air, it was not convenient to prepare synthetic samples. Therefore, two independent methods of analysis were developed to serve as a check for the reliability of these methods. MELT SAMPLING
The method of melt sampling employed depends on the requirements of the material being studied. For some purposes merely drawing a melt sample into a thin glass or silica glass tube and permitting it to freeze has sufficed. For more active samples handling in a dry box may be necessary. I n any case, exposure of the samples to air should be minimized. DETERMINATION OF TOTAL SOLUBLE TITANIUM
A sample sufficient for a 20- to 40-ml. titration is dissolved in 100 ml. of 0.6N hydrochloric acid. The solution is reduced to titanium(II1) [Rahm’s procedure (IS) is convenient] and titrated with standard ferric ammonium sulfate (0.0626N) using ammonium thiocyanate indicator (6). The preliminary reduction of titanium(1V) has generally been found unnecessary when the sample is homogeneous and contains some titanium(II), provided prolonged exposure to air is avoided. Comparative data for total titanium with and without prereduction are given in Table I. HYDROGEN EVOLUTION METHOD FOR TITANIUM(I1)
Reagents and Apparatus. Hydrogen-saturated acid solution is prepared by allowing 1.2N hydrochloric acid t o stand for at least 2 hours in contact with aluminum sticks. The solution must not be tightly capped. This reagent needs to be just sufficiently
Table 1.
Sample KO.
1 2
9 10
Determination of Total Titanium
Total Titanium, Mole per Kg. Reduction Direct titration method 0.021 0.021 0.063 0.058 0.081 0 . OSi 0.111 0.111 0.196 0.198 0.242 0.244 0.265 0,263 0.292 0.292 0.309 0.315 0.344 0.342
acid to avoid hydrolysis of titanium(II1) during solution of the sample. When left in contact with the aluminum sticks, it has been found usable for several weeks. The apparatus consists of a 50-ml. gas buret used as shown in Figure 1. It is calibrated in 0.1-ml. divisions from the upper stopcock. Procedure. The gas collecting bell and buret are filled Fvith acid solution saturated with hydrogen by applying suction t o the buret tip. The tube t o the leveling bottle is also filled and the leveling bottle is partially filled tvith the same solution. A sample sufficient to produce 10 to 40 ml. of hydrogen gas is weighed out rapidly and added to the 400-ml. beaker surrounding the partially raised gas collecting bell; the rounded bottom of the beaker al10n.s the pieces to fall rapidly underneath the gas collecting bell, which is then lowered. As the salt dissolves, any titanium(I1) reacts quantitatively with the acid to yield titanium(II1) and hydiogen: T i + + + H + -+ T i + + +
+ l/tHt
Solution of the salt could be speeded VOL. 30, NO. 12, DECEMBER 1958
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