Abstract: Treating a water system containing or in contact with a metal sulphide scale to inhibit, prevent, reduce, dissolve or disperse iron sulphide deposits. A solution of tris(hydroxyorgano)phosphines (THP) and tetrakis(hydroxyorgano)phosphonium salts (THP+ salts) and sufficient of a chelant (amino-carboxylates or amino-phosphonates) to provide a solution containing from 0.1 to 50% by weight of said THP or THP+ salt and from 0.1 to 50% by weight of said chelant, is contacted with the metal sulphide scale thereby to dissolve at least part of said scale in said solution.

Abstract: Treating a water system containing or in contact with a metal sulphide scale to inhibit, prevent, reduce, dissolve or disperse iron sulphide deposits. A solution of tris(hydroxyorgano)phosphines (THP) and tetrakis(hydroxyorgano)phosphonium salts (THP+ salts) and sufficient of a chelant (amino-carboxylates or amino-phosphonates) to provide a solution containing from 0.1 to 50% by weight of said THP or THP+ salt and from 0.1 to 50% by weight of said chelant, is contacted with the metal sulphide scale thereby to dissolve at least part of said scale in said solution.

Abstract: A composition comprising tris(hydroxymethyl)phosphine or phosphorus-containing salts or condensates of those salts with nitrogen-containing compounds coated or absorbed onto a solid or porous substrate is disclosed. The salts or condensates are based on tetrakis(hydroxymethyl)phosphonium salts. The substrate has a melting point greater than 70° C. and is an optionally hydroxyl-substituted di- or polycarboxylic acid. The compositions may be used with water soluble film forming polymers to make sachets or bags containing sachets or bags of these phosphorous-containing compositions along with sachets or bags of compositions that are incompatible with these phosphorous-containing compositions.