寫眞用添加劑の銀塩に及ぼす作用機構に關する研究 (第2報)

The addition agents here discussed are sensitizers or fog-inhibitors.<BR>In order to elucidate the mechanism of action of sensitizer or fog-inhibitors on AgBr, we studied the adsorption phenomenon or chemical reactivity of the two species of typical sensitizer……thiourea and N, N-diethyl-thiourea……and the two species of typical fog inhibitors……2-amino-4-methylthiazole and 2-diethylamino-4-methylthiazole……to the surface of AgBr crystal.<BR>The quantitative measurements of adsorbed amount were done by the tracer method with use of radioactive S³⁵ in the case of two species of thioureas, and on the other hand by the colorimetric method through the diazocoupling in the case of two species of thiazoles.<BR>The following experiments ((I)..(4)) were executed.<BR>(1) The adsorption experiments.<BR>The solutions of addition agents were prepared in the various concentrations (2×10^-7 mol/cc-4×10^-6mol/cc). Each time a certain fixed amount of AgBr (9.39gr=5×10^-2mol) was added to a certain constant volume (50cc) of the solution, and then the adsorbed amount of addition agents was measured. From these results we obtained the curves of the adsorbed amounts of the addition agents vs. their initial concentrations (or residual Concentraions).<BR>(2) The desorption experiments<BR>The above-mentioned AgBr on which the addition agent was adsorbed was added to a certain constant volume (50cc) of distilled water and the desorption of addition agent adsorbed on the snrface of AgBr was examined. The procedure of extraction was repeated. From these results we found that in the case of thiourea only a part of adsorbed amount was extracted and the rest remaining was unextracted, and in the case of N, N-diethylthiourea its adsorbed amount was 'continuously extracted little by little by the repetition of the extraction procedure. We did not find their desorption in the case of both thiazoles.<BR>(3) The exchange-adsorption experiments.<BR>An attempt was made to find whether or not the addition agents once adsorbed on AgBr could be replaced by and exchanged for the sensitizing dye, when the AgBr was put into the dye solution. We observed that the thiourea and N, N-diethyl-thiourea were not at all replaced by and exchanged For sensitizing dye, but 2-amino-4-methyl-thiazole was replaced by and exchanged For it in part (about 50%), and 2-diethylamino-4-methyl-thiazole was replaced by and exchanged For it completely.<BR>(4) The measurement of AgBr surface area.<BR>The measurement of the surface area of AgBr was done with the sensitizing dye (2, 2- diethyl-8-methyl-thiocarbocyaninebromide)<BR>Summarizing the above results, we concluded that both thioureas react chemically with AgBr, producing the double compound, and 2-amino-4-methyl-thiazole shows the typical monomolecular adsorption on AgBr surface, while 2-diethylamino-4-methyl-thiazole is not adsorbed so remarkably.