The calculation method is applicable to the analysis of products from conventional manufacturing, whose impurities other than sulfates are well known and measured, which constitutes almost all cases. However, in exceptional cases where the presence of significant quantities of soluble impurities other than sulfates, the dosage of which is not planned, is suspected, a check should be carried out using the gravimetric method. The result obtained by this last method will only be retained if the results obtained respectively by calculation and by gravimetry differ by more than 1.7% (m/m) (this value representing the average of the differences found by gravimetry following comparative analyses).
NBN T 03-174-1980 history
1979NBN T 03-174-1980 Sodium sulphate for industrial use - Determination of sulphates content - Calculation method and barium sulphate gravimetric method