825
V O L U M E 2 0 , NO. 9, S E P T E M B E R 1 9 4 8 size of the droplet,sof the mist entering the flame, the surface tension and viscosity of the solutions, and the complexing action of the ions on the alkali metal ions are possible contributing factors. The results presented above indicate that a rather large number of commonly encountered cations, anions, and organic compounds may cause serious interference in the determination of sodium or potassium by the flame photometer if present in certain concentrations. This emphasizes the need for careful consideration of the history and probahle composition of every sample analyzed by this method. Berry, Chappell, arid Barnes ( 2 ) report that it is possible to correct the errors caused by foreign molecules by compounding the standard solutions used in calibrating the instrument in such a manner that these standards contain quantities of interfering substances in proportion to those in the solutions to be analyzed. Others, in using this technique, found that the presence of large amounts of foreign salts made the determination impractical (4).
The authors’ experience in usiiig this modification confirms the latter work and indicates that accurate results are obtained only on relatively simple solutions. Generally, complex substances of unknown composition have been accurately analyzed only after removal of the interfering substances. LITERATURE CITED (1) Barnes, R. B., Richardson, D., Berry, J. W., and Hood, R. L., I N D . ESG. C H E M . , A N A L . E D . , 17, 605-11 (1945). ( 2 ) Berry, J. W., Chappell, D. G., and Barnes, K. B., I b i d . , 18, 19-24 (1946). (3) Hald, P. M., J . B i d . Chem., 167, 499-510 (1947). (4) Overman, R. I
