What precision is required for weighing or measuring? (Copy)

In tests with numerical limits and assays, the quantity stated to be taken for examination is approximate. The amount actually used, which may deviate by not more than 10 per cent from that stated, is accurately weighed or measured and the result is calculated from this exact quantity.

In tests where the limit is not numerical, but usually based on comparison with the behaviour of a reference substance under the same conditions, the stated quantity is taken for examination.

Reagents are used in the prescribed amounts.

For weighing, the precision corresponds to plus or minus 5 units after the last figure stated (for example, 0.25 g is to be interpreted as 0.245 g to 0.255 g).