curves are prepared using the solvent in question to compensate for the density differences between aqueous and organic solutions. Volatile organic solvents decompose the alpha phosphor mounting material making frequent recalibrations necessary. It is, therefore, recommended that samples of volatile organic solvents should not be assayed in this instrument,
ACKNOWLEDGMENT
The authors express their appreciation to C. T. Illsley for his suggestions and assistance on technical problems concerning the counter’s operation. LITERATURE CITED
(1) Byrne, J. T., Rost, G. A., ANAL. CHEM.33, 758 (1961).
( 2 ) Doher, L. W., Chemistry Standards
Laboratory, The Dow Chemical Co., Rocky Flats Division, unpublished procedure manual, 1964. C. R. FORREY K. I. HAWKINS’ The Dow Chemical Co. Rocky Flats Division P. 0. Box 888 Golden, Colo. Present address, Children’s Hospital, E. 19th Ave. and Downing, Denver, Colo.
Dispersion of Samples in Solid Antimony Trichloride as a Method for Infrared Analysis Herman Szymanski, Kenneth Broda, Joan May, William Collins, and Dennis Bakalik, Department of Chemistry, Canisius College, Buffalo, N. Y.
A
NEW SAMPLING technique for infrared spectrometry is described. The technique consibts of utilizing solid antimony trichloride as the matrix in which sample is dispersed or dissolved. The halide melts near 80’ C. and samples for infrared analysis can be prepared by melting the halide in a beaker on a hot plate, adding the sample, pouring the hot liquid onto a salt plate which is heated to a temperature near that of the solution, and allowing the solution to solidify on the plate. d clear film is usually obtained which can be used for the infrared analysis. I n some cases the salt plate may be further heated under vacuum and the halide sublimed off leaving the sample in the form of a cast film. We have found a sufficient number of examples where conventional infrared sampling techniques are not so satisfactory or so simple as the halide one and it is for these samples we recommend this new technique. These samples include materials for which inert solvents are not available and mulling or pelleting techniques are not satisfactory. The halide can also be used as a solvent to study dissociated materials because in many cases associated compounds will dissociate in it. It can also be used as a solvent for casting films onto salt plates for infrared analysis. I t has been recognized for some time that a large number of organic and inorganic compounds will dissolve in antimony and arsenic trihalides (f-14). Inorganics such as FeCI3, AlC13, SeC14, TeC14, KC1, RbC1. CsC1, T1C1. HgC12, KF, KBr, KI. and many others are soluble in the molten halide.
Table 1. Compounds Which Interact with Antimony Trichloride Compounds dissolved without extensive interaction Benzene Manganese sulfateb Acetone Ferrous sulfateb Naphthalene Copper sulfateb Tetraanisylethylene Calcium sulfateb Succinic acida Lithium sulfateb Anisic acida Sulfuric acidb Phenylacetic acida Ammonium sulfateb p-Xitrobenzoic acid0 Arsenic trichloride Glycolic acida Lanthanum trichlorideb Phenol Zinc chloride* Resorcinol Potassium hydroxide Naphthol Boric acidb Propylene glycol Tetrakisparamethoxyphenylethylene Compounds which react extensively Albumin with antimony trichloride 3-Indoleacetic acid 2,4-Dihvdroxyacetophenone Trimethylamine Benzophenone Triethylamine 4,41-Dimethoxybenzophenone Dime thylaniline Trimethylamine hydrochloride o- Aminop henol Dioxane (3) Benzoic anhydride Cholesterol Testosterone 3,4-Toluenediamine Polymeric systems o-Phenylenediamine Phenol-formaldehyde Urea Polyesters Organo phosphorus acids (all types) Polyamides Trimethyl phosphine oxide Polyimides 2,4,4,4-Tetraniet hyl- 1,3-cyclohut anediil Polycaprolactum Polyethylene terephthalate Polymeric systems Polyhexamethylene adapamide Polyphenylene oxide Urea-formaldehyde Polycarbonates Tetrafluorethylene Polyacrylonitrile Polyvinylchloride Polystyrene Nitrocellulose Polymethylmethacrylate Cellulose Polyvinylfluoride Polyethylene Biochemical compounds Polypropylene Uracil (9) 5-Chlorouracil (9) Copper nitrate Thymine (9) Purines ( 8 ) a Spectra represents the dissociated Pyrimidines ( 8 ) compound so dimer bands are not present. Amino acids ( 7 ) * N o PhIR spectra determined here
VOL. 37, N O . 4, APRIL 1965
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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
