What is the dispersant allowed in test method D1140?

In test method D1140, which is used for the determination of the amount of clay and silt in soils, sodium hexametaphosphate is the appropriate dispersant. This chemical is effective in breaking down soil aggregates and separating individual particles, allowing for a more accurate measurement of soil texture.

Sodium hexametaphosphate functions by dispersing colloidal particles in suspension, which is crucial for proper analysis in soil testing. This item plays a vital role in ensuring that the soil sample can be analyzed without interference from clumping or aggregation, which could skew the results.

The other substances mentioned, such as sodium chloride, calcium carbonate, and potassium phosphate, are not used in this context specifically for the purpose of dispersing soil particles as required in test method D1140. Each of these alternatives could have their own properties and uses in different tests or applications, but they do not serve the specific function desired in this standard testing method.