250
amine 1622 pair. The CMC of impure sodium lauryl sulfate and of pure Hyamine 1622 fall within this concentration range. hmphicide titrations of Ivory soap with Hyamine 1622 were made a t room temperature a t different concentrations. Because the equivalent weight, X ,of Ivory was not known, C Y / M was plotted against the concentration of Ivory a t end point in Figure 2; at concentrations greater than 0.270, CY/M remained constant. At low Ivory concentrations, CY/M dropped to low values instead of rising as those shown in Figure 1. Aipparently, at high dilutions, the fatty acid salt hydrolyzed extensively to the inactive free carboxylic acid. Hence less Hyamine was needed a t end point. General Application of Method. Amphicide titration is applicable to a variety of sulfonic and quaternary ammonium amphiphilic materials including certain polyelectrolytes. T h e following sulfonates have been titrated successfully to give sharp end points a t 0.4 to 0.6% concentrations: Benax 2 8 1 (Dow Chemical Co.), Sherosope F-445 (Bryton Chemical Co.), Sulframin ABS (Ultra Chemical
Itu 0.1
0.2
0.3
‘4 I V O R Y AT E N D
0.4
POINT
Figure 2. Effect of dilution on amphicide titration of Ivory soap
up a t concentrations below a critical value. hpparently an excess of the titrating material \+as needed to force the fatty ions together in a common ion effect to form large aggregates. The latter, which separated as a discrete phase, could still have an equimolar composition. This excess of reactant depended on how dilute the misture was and resulted in a large apparent value of CY. The rise in CY occurred a t about 0.1 to 0.2% sodium lauryl sulfate concentration for the sodium lauryl sulfate-Hy-
Works), and poly(potassium sulfopropyl methacrylate) ( 5 ) . Sulframin KE (sulfonic type) and Xrquad 12-50 (quaternary ammonium type, hrmour Industrial Chemical Co.) could not be titrated directly with Hyamine 1622 and sodium laurylsulfate. But sharp end points were obtained when excess titrating solution was added and the excess backtitrated with standard solution of opposite ionic type. LITERATURE CITED
(1) Dreger, E . E.,Keim, G. I., Miles, G. D., Shedlovsky, L., Ross, J., Znd. Eng. Chem. 36,610(1044). (2) Epstein, &I. B., Wilson, J. C. W., Conroy, L. E., Ross, J., J . Phys. Chem. 58,860 (1954). (3)Hwa, J. C. H. ( t o Rohm & Haas Co.), U. S. Patent 2,933,529(April 19, 1960). (4)Miles, G.D.) Shedlovsky, L., J . Phys. Chem. 48, 57 (1944). (5) Niederhauser, W. D., Broderick, E., Owings, F. F. ( t o Rohm & Haas Co.), U.S.Patent 2,964,557(Dec. 13, 1960). (6) Schwartz, A. M., Perry, J. W., Berch,
J., “Surface Active Agents and Detergents,” Vol. 11, p. 338, Interscience, New York, 1958. (7) Swanston, K.,Palmer, R. C., J . Soc.
Dyers Colourists 66,630 (1950). (8) Winsor, P. A., Trans. Faraday Soc. 48, 376, 451 (1948).
Color Quench Correction in liquid Scintillator Systems Using an Isolated Internal Standard H. H. ROSS, Analytical Chemistry Division, Oak Ridge National Laboratory, Oak Ridge, Tenn.
A
article by Ross and Yerick (3) discusses the various problems involved in the interpretation of color quenching in liquid scintillator systems. The authors developed a general mathematical treatment to correlate color interference with the absorption characteristics of the color quenching species. Their model is analogous to the total light absorption of a multicomponent system that follows Beer’s law. Allthough the technique is capable of giving good results for evaluating the combined effects of color and chemical quenching, the authors do not propose that their technique be used to replace conventional methods of quench correction. The method requires a large number of experimental operations and does not lend itself to routine counting problems. The present study describes a new technique of color quench correction using an isolated internal standard. Using this new technique in conjunction with any of the other methods for total quench correction, the separate effects of color and chemical quenching are easily resolved. The isolated internal standard techRECENT
nique is based on the absorption of light photons in a color quenched liquid scintillator sample. However, in contrast to the spectrophotometric method, the light source consists of a small ampoule containing an unquenched liquid scintillator spiked with the desired isotope. The photons emitted by the standard have the same intensity and spectral distribution as those produced in the sample itself. In practice, the isolated internal standard is used in the following manner. After initial construction, the standard assembly is placed in a vial containing a sample of pure liquid scintillator solution. The sample is counted and the resulting activity becomes the unquenched standard count ( A o ) . The standard is now ready for use. .4 sample that exhibits color quenching is introduced into a liquid scintillator and counted in the usual way (As). The isolated internal standard assembly is placed in the sample and counted again ( A c ’ ) . Then:
A,’ - A ,
=
A,
where Q is the degree of color quenching. T o correct the observed activity of the sample for color quenching :
A , (corrected) = A , (obsd.)
Q1
__
[1!
It should be pointed out that different standards are required for each isotope counted. Standards of C14, Cl36, H3, and others are easily prepared. EXPERIMENTAL
Analytical reagent grade and scintillation grade chemicals were used whenever possible. Coloring agents used were F D & C type coal-tar dyes, although not necessarily certified for such use. Stock dye solutions were prepared in toluene; aliquots of these solutions were used for individual measurements. The weight of dye used in each experiment was kept small (
