Take up the ash with 10 ml of 10 % sulphuric acid (4.5) and transfer it with washings of distilled water (4.1) to a 50 ml volumetric flask (5.10), and fill to the mark at room temperature with distilled water (4.1). A 5 ml aliquot of this ash solution is to be used to prepare the sample solution of the photometric phosphate assay.
