Alkali polysulfides, reducing agents

Nitro-filter cloths are composed of cellulose nitrate, which is an ester of cellulose. Any chemical compound that will saponify the ester will destroy the cloth. Caustic soda or potash in strengths of 2% at 70° C or over alkali sulfides, polysulfides and sulfohydrates or mixtures of ethyl alcohol and ether, ethyl, amyl and butyl acetates, pyridine, ferrous sulfates, and other reducing agents are detrimental to the cloth. 

Alkali metal polysulfides are added to stabilize alkaline sulfur dye liquors against atmospheric oxygen. This is common for Hydron Blue, especially on the winch beck. An excess of sulfide and reducing agent in the wastewater has to be avoided therefore, low-sulfide dyeing methodes were introduced [71],... 

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