Turbidimetry can be used in biology to find the number of cells in a suspension. Turbidity-is an expression of optical look of a suspension caused by radiation to the scattered and absorbed wavelength. Scattering of light is elastic so both incident and scattered radiation have same wavelength. A turbidometer measures the amount of radiation that passes through a fluid in forward direction, analogous to absorption spectrophotometry. Standard for turbidimetry is prepared by dissolving 5g of hydrazinium (2+) sulfate(N2H4H2SO4) and 50g of hexamethylenetertramine in 1liter of distilled water is defined as 4000 nephelometric Turbidity Unit(NTU) Application Determination of water Clarity of pharma products and drinks Immunoassay in lab Turbidimetry offers little advantage than nephelometry in measurement of sensitivity in low level antigen a antibody immunoassay. Antigen excess and matrix effects are limitations encountered