Serum sodium and potassium analyses by continuous-flow flame photometry is a well-accepted procedure (1, 2). Recently Habig and Williamson (3) have used the widely available Instrumentation Laboratory Model 143 (IL-143) flame photometer for continuousflow analyses. Pennacchia et al. (4) have operated this flame photometer at rates as high as 120 samples per hour. In both systems the results app...