GB/T 223.61-1988: Methods for chemical analysis of iron, steel and alloy - The ammonium phosphomolybdate volumetric method for the determination of phosphorus content

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Scope

Dissolve the sample with oxidizing acid; at nitric acid acidity of 2.2 mol/L, add
ammonium molybdate to generate ammonium phosphomolybdate deposition;
after filtering, dissolve with excessive standard sodium hydrate solution;
taking phenolphthalein solution as indicator, back-titrate the excessive
sodium hydrate with nitric acid standard solution till the pink just disappears
(the end-point) (about pH8).
The general reaction formula of dissolving ammonium molybdate precipitation
with sodium hydrate is as.
Arsenic of less than 100μg, tantalum < 500 μg, zirconium, vanadium or
niobium < 1 mg, wolfram < 8 mg, titanium < 10 mg and silicon < 20 mg
contained in the test solution, may not interfere the determination; exceeding
the limits above, remove arsenic by hydrochloric acid and hydrobromic acid;
mask zirconium, niobium, tantalum, titanium and silicon by hydrofluoric acid;
reduce vanadium by hydroxylamine hydrochloride; remove wolfram (in
ammonia solution at presence of EDTA) by beryllium carrier.

Basic Data

Standard ID	GB/T 223.61-1988 (GB/T223.61-1988)
Description (Translated English)	Methods for chemical analysis of iron, steel and alloy - The ammonium phosphomolybdate volumetric method for the determination of phosphorus content
Sector / Industry	National Standard (Recommended)
Classification of Chinese Standard	H11
Classification of International Standard	77.08
Word Count Estimation	5,552
Date of Issue	2/5/1988
Date of Implementation	2/1/1989
Older Standard (superseded by this standard)	GB 223.3-1981
Issuing agency(ies)	National Bureau of Standards
Summary	This standard applies to pig iron, iron, carbon steel, alloy steel, phosphorus content. Measuring range: 0. 01 to 1. 0%.