Oxidizability of Common Halides and Applicable Masking Agents in the Dichromate Chemical Oxygen Demand Determination
This study was conducted for the purpose of evaluating the oxidizability of common halides and finding other complexing agents, which can effectively suppress chlorides, bromides and iodides and at the same time minimize the usage of mercuric sulfate. To compare the extent of oxidation of chloride, bromide and iodide, freshly prepared solutions of different concentrations were used in order to see the variations due to concentration. The following are the findings of the study: In the extents of oxidation,(1) chloride was 48.20% oxidized, (2) bromide was oxidized up to 99.40% and (3) iodide was unusual at 553.4% level of oxidation. But, the oxidizabilities of chloride is just about half of the current literature value of 0.226mg oxygen per mg of chloride indicating an overestimation of earlier studies. As far as the masking effectiveness of the complexing agents,(1) mercuric sulfate was effective in totally masking chloride at 760mg but ineffective in totally masking bromide; (2)aluminum sulfate was effective in totally masking chloride at approximately 1930mg but ineffective in totally masking the other halides;(3)ferric sulfate was ineffective in totally masking the three halides even at the maximum amount used of 2500mg;(4)mercuric-aluminum sulfate mixture was ineffective in totally masking the halides;(5)mercuric-ferric sulfate mixture was very effective in totally masking chloride at approximately 380mg but ineffective in totally masking bromide; and(6)aluminum-ferric sulfate was effective in totally masking chloride at approximately 2180mg but again ineffective in totally masking bromide.