M 1727 (OTTO) Mercuric sulphate, GR 99%+ Cas 7783-35-9 - used as the catalyst for the production of acetaldehyde from acetylene and water. M 1727 (OTTO) Mercuric sulphate, GR 99%+ Cas 7783-35-9 - used in medicine as a catalyst and in extracting gold and silver.