To obtain addnl. insight into the release mechanism of the metals in electrothermal atomization at. absorption spectrometry, a quant. relation between the heat of vaporization and the size of the released particles is proposed from the Kelvin equation. The applicability of the equation for the study of Ag and Au vaporization is demonstrated and the limits in which the model is valid are detd. According to the present considerations the activation energy could be equal to the heat of vaporization of the Ag and Au droplets. An explanation of the obsd. dependence of activation energy on analyte mass is given. The proposed relation provides a possibility for definition and evaluation of an effective radius/size of the droplets from their heat of vaporization. A correlation between the mass of the injected sample and the effective radius of the droplets, obtained at higher temp. is found. The min. and max. effective radii of the droplets, followed the proposed equation are calcd. for Ag on pyrolytic graphite coated electrographite (PGC) and Au on PGC, uncoated electrographite (EG) and glassy C (GC) tubes. The results obtained are indirect evidence for the island structure of precursor metal layer and for the existence of Ag and Au microdroplets on the graphite support. [on SciFinder (R)]