The occurrence of ionization of metal vapours introduced into a flame is generally known x). This accounts for a decrease in (atomic) light-emission as it was studied by Huldt2), Smit and V e n d r i k 3). The effects of ionization in the special field of flame-photometry have been outlined by S m i t, A 1 k e m a d e and Verschure4) S)8), and have been discussed, independently, during the general discussion of the symposium of flamephotometry, U.S. A., 1951 8). In this paper the results will be given of some quantitative investigations made by author with an airacetylene flame (described in 5)). Solutions of K and Na as chlorides in 0.15 N HC1 were used in order to make the fractional chlorideassociation independent of the salt concentration, HC1 being present in excess. Special measurements were made to enable correction for self-absorption of the two resonance-doublets chosen.
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The relative emission for potassium (1-4 mg per 100 ml) was determined at heights of 10 and 23 mm respectively above the blue combustion cones centrally in the flame. The logarithmic plot of the emission versus the log of the salt concentration in the liquid, could not be brought into coincidence with the theoretical curve (derived from S a h a' s equation for ~onstant temperature) by any parallel shifting. Moreover, both plots had different slopes, incompatible with the expected constancy of temperature and total K-concentration of the flame over that interval of height.
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The enhancement of K-emission at flame-height of 23 mm due to sodium added at various quantities (corrected for filterleakage, i.e. transmission of Na-light by K-filter) was measured for 1, 2 and 4 mg K per 100 ml respectively, and plotted versus the relative excess of Na. Comparison of these plots with the theoretical curves valid at .the flame teriaperature (2500ยฐK) should yield the absolute concentration of K-atoms + ions in the flame. However, this calculated K flame concentration divided by the K salt concentration in the solution appeared to decrease systematically by