djum fluoroacetate-potassium bromide ranged from 2.6:14:100 to 6.6:19:100 in standard mixtures, and ratios of fluoroacetate-potassium bromide of 1.2 to 100 have been employed for trace amountsin the presence of highly absorbing clays, Under these conditions there is a linear relationship between the ratio of the absorbances of azide and fluoroacetate ICTF) peaks and the ratio of standard to sample concentrations. A further advantage of sodium azide is the short grinding time required to
produce constant standard-sample peak height ratios for identical mixtures. No change in this ratio Occurs after hand grinding for 10 minutes or ball milling for 5 (Figure 2); milling for a longer time has a slight effect on the width of half peak height and decreases the scatter background a little, but has no effect on the height of the azide peak itself. The only disadvantage is the desirability of avoiding large amounts of water and or organic solvents which otherwise might be added to facilitate mixing of the sample and potassium bromide.
LITERATURE CITED
~R.B.,~ G ~~R. ~ e., ~ Williams, ~ ~, , E. F., Linsley, s. G., Peterson, E. M., IND.ENG. CHEM.,ANAL.ED. 19, 620
(1) B
(1947). ( 2 ) Childers, E., Struthers, G. W., ANAL. CHEM.27, 737 (1955). ( 3 ) Kuentzel, L. Ibid.i *’I 301 (l955). (4) McDonald, 1. R. C., Watson, c. Zbid., 29, 339 (1957). ( 5 ) Miller, F. A., Wilkins, C. H., Ibid., 24, 1253 (1952). (6) Wiberley, S. E., Sprague, J. W., C a m p bell, J. E,, zbid,, 29,210 (1957). ( 7 ) jt’right, Norman, A p p i . Spectroscopy 9 , 105 (1955).
Wave length Calibration of Spectrophotometers Ian K. Walker and Harry J. Todd, Dominion laboratory, Department of Scientific and Industrial Research, Wellington, New Zealand
generally experience S’“no difficulty in wave length calibra
