Chicago Chemical Conference HE All-Day Chemical Conference of t h e Chicago Section, T h \ r ~ n ~ CHEMICAL c~~ SOCIETY, was held in Chicago November 25, 1961. hbstracts of t h e papers presented before t h e Inor-
Selection of Solvents in the Ultraviolet Spectrophotometric Determination of Phenols. WALTERMAHLERAND J. ROYDOTY,Bureau of Chemistry, American Dental Association, Chicago, Ill.
ganic a n d Analytical Section a r e given here.
I n water or alcohol solutions (polar solvents) the phenols all show a broad absorption band in the region between 2700 and 3000 A. The bands are too similar to permit identification of a particular phenol and overlap to too great a n extent to permit the determination of one phenol in the presence of another. I n a nonpolar solvent such a s iso-octane the band is generally resolved into two principal peaks, with decrease in band width (Brode, W. R., “Chemical Spectroscopy,” p. 205, 2nd ed., Kew York, John M-iley & Sons, 1943). The ultraviolet absorption curves become sufficiently characteristic to allow the quantitative determination of isomers of substituted phenols. The application of this principle to the determination of phenolic compounds in therapeutic products was described.
New Method for Calculating pH Limits a t the End Point of a Roosevelt College of Chicago, Titration. W. P. CORTELYOU, Chicago, Ill. New. simple mathematical formulas have been developed for calculating the pH when a solution of a n acid, base, or salt has been 99.9% titrated and when i t has been 100.1% titrated, or between a n y other such limits. This provides a considerable improvement in the solution of the problems of indicator selection and feasibility of titration. Rapid Test for the Detection of Groundwood. R. HUBAT.%, .lrmour and Co.. Chicago, Ill.
Ion Exchange Equilibria Involving Fission Products and Thorium SCHUBERT, Argonne National Laboratory, in Uranyl Nitrate. JACK Chicago, Ill.
h new and rapid test for the detection of groundwood (lignocellulose) in paper and other products of wood was described. When aqueous biiodate is applied to paper which contains groundwood, a deep brown stain immediately develops. The same results are obtained by using iodate in dilute mineral acid solution. Experiments were made in order to explain the reaction t h a t takes place.
The reactions between a synthetic cation exchange resin and many of the fission products and thorium in uranyl nitrate have been studied under the following conditions, varying concentration of uranyl nitrate, carrier-free levels of fission products and thorium; and concentration of fission products and thorium varied by addition of carriers, constant uranyl nitrate concentration. A simple mass active formulation describes the results with fair accuracy, except in cases where radiocolloid formation occurs.
Dielectric Indicator for Column Chromatography. DONALD E. LASKOWSKI A N D RICHARD E . PUTSCHER, Armour Research Foundation, Chicago, Ill. Many methods have been used to detect the presence of colorless compounds during the course of a chromatographic separation. The refractive index of the effluent has been widely used by many investigators. Various color-forming streak reagents have also been used. Arbitrary fractionation of the effluent and examination of the solute has been used successfully in a large number of separations. It is sometimes possible to detect colorless compounds by their ultraviolet fluorescence. Troitskii [Biokhimiya, 5 , 375 (1940)l described a device t h a t nieasured the dielectric constant of the material adsorbed on a chromatographic column. Although the method of Troitskii worked, i t was felt t h a t a device t h a t would continuously measure the dielectric constant of the eluate would better serve a s a n indicator for detecting colorless compounds. The work described in this paper is a n evaluation of such an instrument. VaI ious cell designs were described and their performances were shown. T h e use of this instrument in several practical chromatographic separations was described. The instrument used is commercially available and can be used without modification to give excellent results.
Determination of Hydroperoxides in Petroleum Products. WALKER, Standard Oil Co. (Indiana), Whiting, Ind.
D. C.
.In arsenometric method was presented for the determination of hydroperoxides in petroleum products. The method utilizes a twophase extraction and reduction of the hydroperoxides with alkaline sodium arsenite. Excess arsenite is determined iodometrically. Known concentrations of hydroperoxides in gasoline, heater oil, white oil, and wax were determined quantitatively with a reproducibility of *0.01 peroxide numbers less than 1; for peroxide numbers above 1, the reproducibility is within 1%. Results are independent of sample size, which ranges from 10 to 100 ml., depending upon the hydroperoxide content. Means for Increasing Sensitivity of the Beckman DU Spectrophotometer. H . hI. GRCBBASD L. J. SCHMAVCH, Standard Oil Co. (Indiana), Xhiting, Ind. Changes in the amplifier and null circuit which increase the sensitivity of the photometer by a factor of 10 or more were described. This is accomplished without loss of photometering accuracy by adding a n extra stage of amplification. Use of subminiature tubes in the final two stage allows this to be done in the existing amplifier compartment. An extra 15-volt battery required may be housed elsewhere.
Several New Methods of Analysis with a Rotating Mercury Electrode. T. S. LEE, University of Chicago, Chicago, Ill. T h e electrode consists of about 0.1 ml. of mercury in a round Bakelite cup t h a t is rotated a t 200 to 1800 r.p.m. Electroreducible and electro-oxidizable substances in aqueous solution yield current-voltage curves (waves) similar to those obtained from the dropping mercury electrode. T h e height of the wave is proportional to concentration and can be used t o determine, with a n accuracy of about 1 t o 2y0,electroreducible substances a t concentrations a s low a s 5 X 10-7 M-e.g., 0.06 p.p.m. of cadmium ion. Theoretical equations for the shape of the wave have been derived and verified. A coulometric method has been devised for the determination of metal ions a t concentrations a s low as 7 X 10-9 iM--e.g.. 0.8 part per billion of cadmium. A constant reducing potential is applied to the rotating electrode for 15 minutes. During t h a t time some of the metal ion is reduced and accumulates in the mercury. A less reducing potential is then applied and the amount of electricity t h a t corresponds to the redissolution of the metal is measured. From this quantity the concentration can be calculated with an accuracy of 1 to 5%; Similar methods can be used to analyze mixtures of metal ions t h a t have half-wave potentials differing by as little a s 30 mv. This is made possible by the proper selection of the potentials applied for accumulation and dissolution. T h e first and higher derivatives of the current-voltage wave can be obtained by suitable electrical circuits as described b y 0. Muller. T h e derivative curves are useful in the analysis of mixtures, a s mixtures t h a t would yield overlapping current-voltage waves give derivative curves consisting of separated peaks.
Analysis by Differential Electrical Migration in Polyphase Systems. HAROLD H. STRAIN, T. R. SATO,A N D W.P. NORRIS, Argonne Xational Laboratory, Chicago, Ill. T h e differential migration of solutes produced by flow of solvent in a polyphase system forms the basis of the widely applicable chromatographic adsorption analysis. Analogous separations are now being made in polyphase systems when electrical current produces the migration of ionized or charged solutes. This differential electrolysis is carried out conveniently in media such a s moist paper, gels, and beds of porous filter aids, ion exchangers, etc. The separability of some mixtures may be increased by electrolysis in one direction in one solvent followed by transverse migration in another solvent. Separations may be made continuously b y the flow of solvent transversely to the simultaneous flow of electrical current. I n all these applications of differential electrical migration, the effect of the electrode reactions and the separability of the mixtures depend primarily upon the solvent, the electrolytic solution. These migration methods have been applied to the separation of mixtures of various organic and inorganic substances such a s organic acids and inorganic anions and cations. Separations may be made qualitatively or quantitatively. The migration behavior of many ions indicates the formation of unexpected complex substances in the solutions.
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ANALYTICAL
c H E M 1's T R Y
Automatic Coulometric Titrations with Externally Generated ReaN. PITTS, E. A. SCHMALL, gents. Applications to Iodometry. JAMES D O N ~ LDD. DEFORD,Northwestern University, Evanston, 111.
tion number of 4 and a planar configuration. T h e difference is not so great as might be anticipated from a consideration of molecular models.
An automatic instrument for the performance of coulometric titrations with externally generated reagents has been employed successfully for the titration of arsenic (111) with electrolytically generated iodine. The use of a new type, single-arm, generation cell, and a cure n t of 100 ma. gives precisions and accuracies of the order of ~k0.275 on samples in the range from 0.15 to 0.6 me.
Relation of Electronic Density to Chemical Combination. SANDERSON, State University of Iowa, Iowa City, Iowa.
ASD
5,7-Dihydroxy-4-methylcoumarin a s a Fluorescent Indicator. PODALL, Edwal Laboratories, Inc., Ringwood, Ill. HAROLD 5,7-Dihydroxy-4-methylcoumarinhas been found to exhibit interesting fluorescent properties in dilute aqueous solution. If the p H of an acid solution of the compound is gradually increased by the addition of a base, a sharp and intense increase in fluorescence occurs. The change occurs in the p H range of 5.5 to 5.8 and is reversible. Under ultraviolet irradiation the fluorescence is intense enough to be observed in daylight. This change in fluorescence with a change in the p H of the solution has suggested the possible use of this coumarin as a fluorescent indicator in acid-base titrimetry. Trial of the compound with the use of 0.01 A' and 0.1 N acids and bases gives precision of 0.3% or better in observation of the end points. End points are more easily observed than in similar titrations with phenolphthalein. The coumarin can be used in concentrations of 10-4 to 10-275,the more dilute solutions giving sharper changes in fluorescence. 5,7-Dihydroxy-4-methylcoumarinmay be especially useful in acid-base titrations of murky, colored, or very dilute solutions. It is a good substitute for pnitrophenol a s a n indicator. Other fluorescent indicators were also discussed. Coordination Number of the Nickelous Ion. LEOXARD I. KATZIN. .-lrgonne National Laboratory, Chicago, Ill. I t is known t h a t cobaltous ion can show two coordination numbers, 6 and 4. The latter is found with moderately strong complexing agents, and with solutions of the halide or thiocyanate salts in organic solutions. The higher coordination number is characteristic of aqueous solutions, organic solutions of the nitrate, etc. Xickel forms both hexahydrated salts and complexes with four groups attached, and a transition between the two coordination numbers should be demonstrable. This is found on comparing the complexes of the ion with the several halide ions, in organic solution. Spectrophotometric inveetigation shows the complexes with the iodide ion retain the higher coordination number in large part, while the chloro complexes and thiocyanate complexes have the lower coordination number. This indicates the drop in coordination number to be somewhat more difficult than for cobaltous ion. Interactions of Divalent Cations with Substituted Ethylenediamines.
R. KEXT MDRMANNA N D FREDB.430~0,Northwestern University, Evanston, Ill. The formation and complexity constants have been measured a t O o and 25' C. for copper(I1) and nickel(I1) complexes with ethylenediamine, and N-methyl, N-ethyl, *V-isopropyl, and .&',Ar'-diethylethylenediamine in 0.5 M potassium nitrate-water solution. The method of Bjerrum was used, appropriately modified to suit present requirements. I n addition, the thermodynamic quantities A H O , AFO, and A S o have been evaluated for each reaction in the stepwise formation. Since the basicities of the amines are nearly equal, steric hinderance was expected to exert a large influence on the formation constants. T h e magnitude of this steric effect was the present concern. Both the formation and complexity constants indicated t h a t the steric effect overshadowed the much smaller base strength effect. Nickel(I1) complexes, having a coordination number of 4 and 6 , tetrahedral and octahedral configurations, respectively, exhibit greater steric hindrance to their fermation than does copper(I1). which has a coordina-
R. T.
The chemical inactivity of atoms of the inert elements is Lonsidered to be related not only to their particular number and distribution of electrons, b u t also to the particular average density (ED) of their electronic atmosphere. A "stability ratio (SR)" is defined a s t h e ratio of the average density of a n atom or ion to t h a t of a n isoelectronic (real or hypothetical) inert element atom. Unit SR thus represenb maximum stability. SR values are a measure of relative electronegativities of both atoms and simple ions. This paper discussed the application of SR values toward explaining many common chemical phenomena, including the bond "shortening" usually ascribed to resonance among single covalent and ionic or multiple covalent bond structures, and the chemical reactivity of atoms and their ions. Silyl and Silylmethylamines a s Bases. The Double Bond Character of the Silicon-Nitrogen Bond. SEI SUJISHIAND SAMUEL WITZ,Illinois Institute of Technology, Chicago, Ill. I t is generally assumed that the silyl group has a greater + I effect than the methyl group. However, it is found t h a t trisilylamine is a much weaker base than trimethylamine (Burg). This has been attributed to the stabilization of the trisilylamine by resonance of the electron pair on the nitrogen atom with the vacant L-orbital in the silicon atom. I n order to observe whether the silyl group has a n y tendency to increase the base strength, i t was of interest to study the base strengths of the series of amines in which methyl groups are systematically replaced by silyl groups. For this purpose dimethylsilylamine and methyldisilylamine were synthesized. Dimethylsilylamine has not been previously isolated. I n comparison to tho other silylamines, dimethylsilylamine has some unusual properties. Trimethylamine is known to form a reaction stable addition compound with trimethylboron (Brown and Taylor). Dimethylsilylamine has been found to combine with trimethylboron, b u t this compound is much more dissociated than the trimethylamine compound Methyldisilylamine has been found not to combine with trimethyiboron, even a t - 112O C. A. Burg has previously reported t h a t trisilylamine does not combine with trimethylboron. Hence, with trimethylboron a s reference acid, replacement of even one methyl group in trimethylamine leads to a considerable decrease in the basic property. This supports the interpretation t h a t resonance effects mask a n y inductive (+I) effect that the silyl group may possess. The reactions of the silylamines with boron trifluoride and hydrogen bromide have also been studied. The results lead to the same con. clusion a s do the experiments with trimethylboron. Self-Diffusion in Solid Sodium. K.H . NACHTRIEB, J. A. WEIL, E . CATALANO, A X D A. W. LAWSON, Institutef or the Study of Metals, University of Chicago, Chicago, Ill. Measurements were reported for the self-diffusion of solid sodium a t 1 atmosphere pressure over the temperature range 0' to 95' C. T h e data fit the empirical equation D = 0.320 exp (- 10,65O/RT) with a n uncertainty of +300 cal. mole-' in the heat of activation. The entropy of activation calculated from the temperature coefficient of the elastic modulus is 7.7 E.U., and is in good agreement with the value based upon the vacancy mechanism. Measurements of the diffusion rate a t high hydrostatic pressures were interpreted in terms of the vacancy model for diffusion. A correlation was found between the diffusion coefficient and the melting point of sodium as a function of pressure. I t was shown t h a t for BOdium and a number of other cubic metals the heat of activation for self-diffusion is proportional to the latent heat of fusion.
