BS 5551-4.2.2:1987

The methods use a hydrochloric acid/nitric acid mixture and a sulphuric acid/nitric acid mixture. Specifies reagents, apparatus and procedure.

This Subsection of BS 5551 specifies two methods for the extraction of phosphates soluble in mineral acids to produce a test solution for subsequent use in the determination of phosphates content. The two methods use different acid mixtures; a mixture of hydrochloric acid and nitric acid (method A) and a mixture of sulphuric acid and nitric acid (method B).

Method A is a simple routine method which is not affected by the presence of calcium. Method B, which is equivalent to that in the Fertilizers (Sampling and Analysis) Regulations 1978, can give problems due to the precipitation of calcium sulphate during dilution.

The methods are otherwise applicable to all phosphate fertilizers and to mineral phosphates containing low amounts of organic matter.

NOTE. The titles of the publications referred to in this standard are listed on the inside back page.