However, is not a standard material in common deep feature databases. It may be:

was a workhorse product for decades—reliable, predictable, and effective for standard cooling water applications. However, the water treatment industry has evolved toward lower phosphorus footprints, digital monitoring, and multi-functional chemistries.

– Possibly related to Nalco (Ecolab) water treatment chemicals, where “131” could be a product series (e.g., NALCO® 131 corrosion inhibitor or cooling water additive). The “S” might denote a special formulation (e.g., sulfur-containing or stabilized).