- 作者: 孫炳榕
- 作者服務機構: Contribution from the Department of Chemistry, National Taiwan University
- 中文摘要:
Two methods using gallein as indicator for the direct titration of lead with disodium salt of EDTA have been developed. In one method, the titration of lead was effected in a weakly acidic medium, using pyridine or hexamethylene-tetramine as buffer. The optimum pH for the titration was found to be at pH 5.5 to 6.0.
Gallein indicator undergoes color change from purplish blue to red. In proceeding the titration within the pH range mentioned above, and in the presence of equimolar concentration of magnesium and alkaline earth metals as well as monovalent cations, no interference was observed.
In the other method, the titration of lead was carried out in the presence of Rochelle salt, using ammonia and ammonium chloride buffer to keep the solution at pH 10. Sharp color change from violet to deep magenta red was observed at the end point. Only univalent cations, such as sodium, potassium, lithium, ammonium or silver did not show interference with the titration. The use of some masking agents has also been demonstrated. - 英文摘要: --
- 中文關鍵字: --
- 英文關鍵字: --