PROCESS MONITORING DURING ELECTROCHEMICAL PRODUCTION OF POLYSULFIDES BY ONLINE FIA USING A CAPILLARY FLOW-THROUGH CELL

We have developed an on-line flow injection analysis (FIA) method for monitoring sulfur species during electrochemical production of polysul fides. By using a capillary flow-through cell, we can reduce the dilut ion of the sample and the influence from oxygen dissolved in the dilue nt can be minimised. The obtained UV absorption spectra give new insig hts into the behaviour of polysulfide during their electrochemical pro duction. The absorptivities at 340 to 400 nm of zero-valent sulfur in different polysulfides species vary with chain length. Polysulfides wi th a longer sulfur-chain have a larger mean absorptivity than those wi th a shorter chain. This opens the possibility to obtain information a bout the fractionation between different polysulfide species during th e process, During the process the chain length also increases after si de reactions has come to dominate. This implies that the side reaction acts primarily upon short chain polysulfides. A new isosbestic point for polysulfide excess sulfur has also been found.