Microdetermination of sulphate and organic sulphur: potentiometric back-titration using simple coated-wire electrodes

✍ Scribed by J. Kalous; D. Brádova; K. Vytřas

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 438 KB
• Volume: 283
• Category: Article
• ISSN: 0003-2670
• DOI: 10.1016/0003-2670(93)85277-q

✦ Synopsis

A method is described for the determination of sulphate, based on precipitation with barium(B) chloride followed by potentiometric back-titration of the excess of barium(B) salt with sodium tetraphenylborate in the presence of polyethylene glycol. To monitor the titrations, simple ion-selective electrodes of the coated-wire type were prepared using an ordinary aluminium conductor, coating the central wire with the membrane formed by plasticized poly<vinyl chloride). The determination of organic sulphur consists in burning the sample in a flask filled with oxygen. The combustion products are absorbed in alkaline hydrogen peroxide and, in an aliquot, the sulphate formed is determined. The procedure was tested on eleven organic substances and applied to the determination of sulphur in samples of asphalt. Compared with visual detection of the end-point of the direct titration of sulphate with barium(B) salt, the results are of the same precision and accuracy. The use of simple potentiometric sensors of the coated-wire type allows objective end-point evaluations and makes the procedure inexpensive.