The methods were investigated which were capable of separately giving reduction sensitization, and Sulfur sensitization to the stage of the second ripening of the photographic emulsion. The emulsion used contained a small quantity of gelatin and was treated with benzen sulfonyl chloride as a precipitating agent, so the effects of natural gelatin on the emulsion were considered as negligible, or this emulsion was regarded as inactive. Therefore, Sulfur Sensitization and silver ripening which improves Wood's method were independently examined. Then, several noted addition agents, which are 5-methyl-7-hydroxy-1, 2, 4-triazolo [2, 3-a] pyrimidine [I], 5-methyl-7-hydroxy-1. 2, 3-triazolo [4, 5-d] pyrimidine [II], benztriazole [III], 6-nitrobenzimidazole (IV) and 1-phenyl-5-mercapto-tetrazole [V], were incorporated in the emulsion and their effects were obserbed. In the reduction sensitization, [I] and [II] showed the inhibition effect with slight desensitization. In th sulfur sensitization, [I], [II] and [III] showed the inhibition effect, [III] accompanied by desensitization. The effects in each sensitization procedure of the compounds described in the previous and present papers are as follows.