This paper describes the construction, operation and performance of an instrument designed primarily for the determination of sodium and potassium. The sample is atomized with compressed oxygen and sprayed directly into an oxygen-butane flame. Backfiring has been eliminated. The stainless steel burner-atomizer unit can be easily dissembled for cleaning when required. The photometer employs narrow band filters and emission type photocells, a separate cell is used for sodium and potassium respectively. The use of two cells of different spectral sensitivity effects a preliminary separation of the two regions of the spectrum in which the characteristic emissions lie. The primary photocell current is amplified and its value obtained from a potentiometer reading. Calibration is substantially linear at the routine sample concentration of 3-7 p.p.m. of either element. Triplicate determinations agree to within one division of the potentiometer dial (100 divisions). Sample consumption is 0.5 ml./min.

Standardization and readings for the sample can be made in a few minutes.