Analysis of acid volatile sulphide and pyrites using microdiffusion

The microdiffusion method published by Brouwer and Murphy([1]) for analysis of acid volatile sulphide (AVS-chiefly FeS) has been extended to both AVS and FeS(2)in a two step process. For the first step (AVS analysis), excelle nt recoveries (similar to 100%) are obtained for Na2S, FeS, PbS, CdS, and Z nS provided diffusion times are long enough. Recovery from other insoluble metal sulphides (Ag2S and HgS) were low, while for CuS were variable. In th e second step, recoveries were similar to 100% for ground, crystalline FeS2 . This work re-emphasises the importance of adding a sufficiently strong re ducing agent during AVS determination in sediments to prevent oxidation of S-2-by Fe3+ produced in the acid dissolution of ferric phases. The method i s amenable to adoption to different apparatus provided recoveries and react ion times are checked with suitable standards.