As an infrared solvent molten antimony trichloride has been used to study extensively many biochemical compounds (7-9). In this work cells with path lengths up to 5 cm. were used with solutions in the range of 0.0002M. However, the corrosive action of the molten halide made it necessary to utilize silver chloride windows and the cells had to be remade after only a few runs. Some authors have reported on the solubility of polymers in antimony trichloride (23). This work has shown that the structure of the polymers was retained in the halide solutions. Use of halide solution as a casting solvent for polymers has been patented by other workers ( 2 ) . The explanation generally accepted for the solubility of the large number of compounds in the halide is that its solvent action is similar to water, with the C1- ion of the halide solutions equivalent to the H f ion in water reactions (6). For many compounds the interaction with the halide is weak and P M R and I R spectra of the compound in the halide are similar to those found for the compound dissolved in inert solvents. For associated compounds the spectra are often similar to those found for the dissociated compound. I t is for compounds which show weak interaction with the halide that its use as a matrix is recommended. I t is not always obvious when the
interaction will be weak or strong but, in general, if an N H or -0group occurs in the molecule there is a possibility that strong interaction will occur. For compounds having a double-bonded oxygen the interaction can be weak to strong. Thus, for acetone dissolved in the halide the carbonyl stretching frequency appears at 1720 in the infrared spectrum. Other workers report it a t 1712 for the Raman spectrum of acetone in the liquid halide (2 4 ) . These same authors report a P=O shift of 131 cm.-l for (CH&PO in antimony trichloride compared to the position in the compound run neat. I n this work these authors discuss in detail the type of interaction which occurs between donor molecules and antimony trichloride, pointing out that it is difficult to predict if the interaction will be weak or strong. We have examined a number of compounds in the halide and in Table I list first those compounds whose infrared spectra are unchanged by the solvent, and then, those compounds whose spectra are changed. The list includes compounds which have been reported by others as soluble in the halides. These examples are referenced. Whenever possible for the compounds examined by these authors, proton magnetic resonance spectra were also determined of the compound in the molten halide. These PAIR spectra gave further evidence if the interaction was strong or
weak. All infrared spectra determined were run in the solidified halide. Attention should be directed to several examples where oxygen or nitrogen does occur in the compound structure but the interaction is of the weak typefor example, the polyimide polymer. These compounds were examined in detail; the interaction is definitely of the weak type although this may not be expected. LITERATURE CITED
(1) Anderson, L. H., Lindquist, I., Acta Chem. Scand. 9, 79 (1955). ( 2 ) Caprio, A. F., U. S.Patent 3,081,273 (March 12. 1961). (3) Daasch, L. W., Spectrochim. Acta 1959, p. 726. (4) Gutman, V., 2. Anorg. Allgem. Chem. - - 5 , 331 (1951). ZO( ( 5 ) J ande,r, V. G., Gunther, K., Ibid., 297, 6 I,1958). (6) Jandemr, Y.G., Swart, K. H., 2. Anorg. Allaem. Chem. 301. 54 11959). ( 7 ) Licher, J. R., Bitner,'J. L:, Emery, D. J., Seffl, h1. E., Park, J. D,, J . Phys. Chem. 59, 615 (1955). (8) Lacher, J. R., Bitner, J. L., Park. J. D., Ibid., p. 610. 19) Lacher, J. R.. Carnoion. D. E..' Park. ' J. D., Shence 110, 360 (1949). (10) Lacher, J. R., Croy, V. D., Kianpons, A., Park, J. D., J . Phys. Chem. 59, 206 (1954). (11) Lindquist, I., Acta Chem. Scand. 9, 73 (1955). (12) Puente, E. C., Anales De Fisica Y Quimica LVIIB 259 (1951). (13) Szymanski, H., Collins, W., Bluernle, A., J . Polymer Sci., Part A , in press. (14) Zackrisson, XI., Alden, K. I., Acta Chem. Scand. 14, 994 (1960).
Silver Chloride Disk Technique in Infrared and Visible Spectrometry Louis L. Pytlewski and Vincent Marchesani,' Department of Chemistry, Drexel Institute of Technology, Philadelphia, Pa.
of silver chloride pressed disk as U an effective substitute for the tassium bromide disk in infrared specSE
PO-
trometry has been under study at this laboratory for some time (1). The insolubility of silver chloride in water and its resistance to chemical attack by a large number of substances have suggested its use over a broad spectrum of analytical applications. An investigation of the use of pressed thallous bromide, thallous chloride, and silver chloride disks as solid sample supports in infrared absorption spectrometry has been reported ( 4 ) . Poor results were claimed for the silver chloride disk only on the basis of the discoloration of the material on exposure to light and a Eingle infrared spectrum of a 1% dispersion of the calcite form of 1 Present address, Rohm and Haas Chem. Co., Bristol, Pa.
618
ANALYTICAL CHEMISTRY
calcium carbonate in silver chloride. Contrary to the above report, our studies have shown that the pressed silver chloride disk is effective not only as a support for liquid films but also as a transparent carrier for the spectral analysis of a large number of organic and inorganic solids. Studies now under way a t this laboratory have already shown that the silver chloride pressed disk technique can be of great significance in the spectral investigation of a large number of compounds containing absorbed and/or chemically bound water-e.g., hydrates, clathrates, metal-organic complexes containing water or other highly polar ligands, biochemical substances extracted from animal and vegetable specimens, the structure of solvated molecules and ions, etc. Furthermore, the hygroscopicity of potassium bromide has often raised serious doubts about
the interpretation of the infrared spectra of hydroxylic compound using a potassium bromide disk sample support (3). The use of silver chloride as a sample support for aqueous solutions has been demonstrated to be effective. h recent paper describes the use of the pressed silver chloride disk for the spectral analysis of aqueous polymer suspensions (3). EXPERIMENTAL
The basic technique of producing pressed silver chloride disks is essentially the same as that used for POtassium bromide and is described in a publication by R. K. Metzler (3). Detailed studies have produced some additions and modifications. The drying and screening of reagent grade silver chloride powder (Mallinckrodt) x a s wholly unnecessary and, indeed, detrimental for the production
of good, clear, water-white disks. Storage of the silver chloride in a desiccator is also unnecessary (no water bands were detected in blank silver chloride disks after approximately 1 year of constant use without desiccation). The soft, elastic characteristic of the silver chloride crystal allows good pellets to be pressed at pressures as low as 8000 p.s.i., thus eliminating the need for a n elaborate hydraulic press. The corrosive effect of silver chloride on the metals used in the infrared disk sample holder (supplied with the PerkinElmer infrared spectrophotometer Model 137) and the KBr pellet die were eliminated with Teflon (Du Pont). Infrared disk sample holders were constructed of Teflon and wafer-thin, circular, highly polished Teflon disks were inserted in the die above and below the powdered sample to be pressed. I n addition, disks made of Teflon used in the pellet die functioned as effective die-mold release agents. (Teflon was well applied to production of potassium bromide pellets with reference to prevention of the breaking of pellets in their preparation and mounting.) DISCUSSION
Excellent qualitative and quantitative infrared spectra of a large number of the organometallic compounds of germanium ( I ) , tin, and silver prepared a t this laboratory were obtained in solution and as pure liquids and solids. The question of whether the appear-
ance of small amounts of water in a spectrum is a result of disk preparation or a result of the hygroscopicity of potassium bromide and sodium chloride is solved with a comparison silver chloride disk. A homogeneous distribution of a solid sample in silver chloride disk is obtained by mulling the silver chloride with a solution of the solid to be analyzed spectrally (including aqueous solutions) and removing the solvent with high vacuum distillation apparatus. Exceptional control of concentrations of solids in the pressed disk is made possible by this method. The plasticity of silver chloride suggested its use as a good inorganic binder for large amounts of solid samples. Silver chloride pellets were made in which the amounts of solid sample far outweighed the silver chloride. Silver chloride disks containing tetraphenyl porphyrin in concentrations high enough to produce pellets almost opaque to visible light were completely transparent in the infrared region of 2.5 to 16 microns and produced exceptional solid state porphyrin infrared spectra. Silver chloride sample disks used for infrared spectra were transferred to a PerkinElmer visible-ultraviolet spectrophotometer Model 202 directly, and good visible spectra were obtained on the same pellets. This eliminates the errors inherent in making up new samples, especially with reference to slight changes in concentration.
Contrary to popular belief, the photodecomposition of silver chloride does not take place in the infrared region. The darkening of silver chloride on exposure to visible and ultraviolet radiation does not appear to effect the transmission of infrared radiation to any appreciable extent. Silver chloride disks were exposed to fluorescent lighting for a period of 10 days and no significant change was observed in the infrared base line. The simplicity of preparation of the silver chloride disk and its extraordinary resistance to physical abuse would suggest it to be a valuable addition to the study of infrared techniques in undergraduate instrumental methods of anallr s'is courses. Silver chloride's broad spectral transparency in the infrared and visible regions of the electromagnetic spectrum and its inertness to a wide category of compounds, combined with the extreme ease of pressing clear pellets, certainly recommend it as an important component to any well equipped spectrometry laboratory. LITERATURE CITED
( 1 ) Anderson, H. H., Znorg. Chem. 3, 910 11964). ( 2 ) Farmer,' 5'. C., Spectrochim. Acta. 8, 374 (1957). ( 3 ) Rletzler, R. K., ANAL. CHEM.36, 2378 (1964).
(4) Smallwood, S. E. F., Hart, P. B., Spectrochim. Acta. 19, 285 (1963).
The authors thank Drexel Institute
for In-House Research Grant S o . 6.
Amphicide Titration of Amphiphilic Compounds Jesse C. H. H w q l Rohm and Haas
Co., Research Laboratories, Philadelphia 37, Pa.
A
is usually analyzed by titrating it with another surfactant of the opposite ionic type. Most procedures involve the use of a color indicator (6). Swanston and Palmer observed a n end point where a flocculent precipitate separated from solution (T), but quantitative aspects of this titration were not fully described. This work concerns quantitative analysis of a broad class of amphiphilic compounds by an amphicide titration method. (Winsor in 1948 defined amphiphilic as ". . . possessing in the same molecule distinct regions of lipophilic and hydrophilic character.") An amphiphilic material, which can also be a surfactant, is not necessarily surface N IONIC SURFACTANT
1 Present address, Stauffer Chemical Co., Eastern Research Center, Dobbs Ferry, N. Y .
sodium lauryl sulfate, Sipon W D (Alcolac Chemical Corp.), was also used. Each batch was standardized before use. Hyamine 1622 (Hy), octylphenoxyethoxyethylbenzyldimethylammonium chloride monohydrate (Rohm and Haas Co.), was 98.8y0 pure. Except a t the place noted, its solution was standardized against pure sodium lauryl sulfate. EXPERIMENTAL Ethylene bis(dodecenyldimethy1Materials. A sample of 1 0 0 ~ o ammonium chloride) was prepared by a known urocedure (~, 3 ) . m.u. 195' to pure sodium lauryl sulfate (SLS), 196.5' C. obtained from Colgate-Palmolive Co., Ivory soap, Procter and Gamble Co., Jersey City, N . J. (courtesy of J. F. is a commercial fattv acid soau of unGerecht), was prepared by the method identified composition. of Dreger et al. (1) and was purified Deionized water was used in all cases. by extraction with Skellysolve F and Titration Method. T h e titration then by recrystallization from ethanol. procedure was simple and reproduciI t s absolute purity was established by ble. About 20 ml. of 0.5 to 1.0% the absence of a minimum in the surface aqueous solution of the material to be tension-concentration curve ( 4 ) , and by titrated was placed in a beaker a t a low film-drainage transition temperaroom temperature. The titrant, ture (
