Formazine

Formazine is a synthetic polymer used as a primary turbidity standard for calibrating nephelometric turbidity meters in water quality analysis. It provides a stable, reproducible reference against which measurements of suspended solids in water can be compared. The standard is expressed in nephelometric turbidity units (NTU), a scale tied to light scattering at 90 degrees.

Formazine standards are typically supplied as ready-to-use suspensions or as two-component solutions. They cover a range of turbidity values, commonly including low and mid-range points such as 20, 100, and 400 NTU, with 0 NTU serving as a baseline. The exact values and instructions are defined by national or international standards bodies (for example ISO or EPA) and by manufacturers.

Formazine suspensions are relatively stable when stored in opaque or amber containers at controlled temperatures and protected from light. Over time, exposure to light, heat, or agitation can cause changes in the assigned NTU, so many suppliers recommend periodic verification and, if necessary, preparation of fresh standards.

Safety and handling: Formazine is a chemical used in laboratory settings. Handle with standard lab precautions, avoid creating respirable dust, wear gloves, and dispose of waste according to local regulations. The material is not considered highly toxic but should be used with appropriate care.

See also: Turbidity, NTU, nephelometry.