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,
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 .
Philadelphia 37, Pa.
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 (
