摘要或動機

硫代硫酸鈉在鹽酸中會產生自身氧化還原反應。溶液維持一段時間的澄清透明，突然快速析出硫微粒而顯得白色混濁，同時顯現廷得耳效應。溶液維持勻相的時間稱為延遲時間，其長短隨起始物濃度與溫度而異。在反應溶液中添加界面活性劑可有效增長延遲時間。以UV-Vis光譜儀分析反應溶液的吸收度變化，界面活性劑的濃度夠高時，延遲時間的倒數與添加界面活性劑濃度的倒數成簡單正比關係。此速率定律式符合界面活性劑與硫核微粒結合形成保護核的機制。陽離子性的界面活性劑如CTAB，明顯地較陰離子或中性界面活性劑有較佳的保護效果。IR及X光繞射光譜分析顯示CTAB與硫微粒有共沉澱的現象。The thiosulfate ions undergo disproportionation in hydrochloric acid to form sulfur. The reaction solutions remain clear first, followed with sudden formation of discrete particles that are observed by the appearance of Tyndall beam. The induction periods vary upon the initial concentration of the reactants and temperature. Addition of surfactant to the reaction solutions significantly prolongs the induction period, indicating the association of surfactant molecules with the nuclei of sulfur particles can hinder the aggregation of sulfur particle-nuclei. The UV-visible spectrophotometric measurements for the formation of sulfur particles in the presence of various surfactants show that the reciprocal values of induction period are proportional to the reciprocal of surfactant concentrations. Such a rate law is elucidated by an associative pre-equilibrium mechanism. The surfactant molecules appear to effectively protect the nuclei of sulfur particles from aggregation. The cationic surfactant such as CTAB demonstrates better "protection" ability than do the anionic or neutral surfactants. The IR and X-ray diffraction analysis indicate that CTAB can result in co-precipitation with sulfur, also supporting the suggested mechanism.