Soil Hydrometers, Sedimentation Cylinder, Mechanical Stirring Apparatus, Sodium Hexametaphosphate, and Constant Temperature Bath are the basic equipment needed for hydrometer analysis. These products all meet ASTM D422 and AASHTO T 88. Tests for complete particle size distribution in soils require sedimentation methods to determine silt and clay fractions. Soil specimens are mixed in a solution of water and sodium hexametaphosphate. Hydrometers are used to measure suspended solids in sedimentation cylinders over time periods of up to twenty four hours.