GB/T 8572-2010Determination of total nitrogen content for compound fertilizers titrimetric method after distillation (English PDF)

Foreword

This Standard is one of the series of standards for compound fertilizers test methods.

These series of national standards are listed below.

- GB/T 8571-2008 "Preparation of laboratory samples for compound fertilizers";

- GB/T 8572-2010 "Determination of total nitrogen content for compound fertilizers

titrimetric method after distillation";

- GB/T 8573-2010 "Determination of available phosphorus content for compound

fertilizers";

- GB/T 8574-2010 "Determination of potassium content for compound fertilizers

potassium tetraphenylborate gravimetric method";

- GB/T 8576-2010 "Determination of free water for compound fertilizers - Vacuum

oven method";

- GB/T 8577-2010 "Determination of free water for compound fertilizers - Karl

Fischer method";

- GB/T 24890-2010 "Determination of chloride content for compound fertilizers";

- GB/T 24891-2010 "Determination of particle size for compound fertilizers".

This Standard modifies and adopts the International standard ISO 5315.1984

"Fertilizers - Determination of total nitrogen content - Titrimetric method after

distillation".

Main differences between this Standard and ISO 5315.1984 are.

- In the absence of amide nitrogen, the reduction method for nitric acid nitrogen is

modified from chromium powder to nitrogen alloy;

- The standard titration concentration of sodium hydroxide is modified from 0.1 mol/L

to 0.5 mol/L.

This Standard replaces GB/T 8572-2001 "Determination of total nitrogen content for

compound fertilizers titrimetric method after distillation".

Main difference between this edition and the previous edition is. the standard format is

rewritten according to the rules of standardization work.

This Standard is proposed by China Petroleum and Chemical Industry Association.

This Standard is under the jurisdiction of National Technical Committee on Fertilizers

Determination of total nitrogen content for compound

fertilizers titrimetric method after distillation

1 Scope

This Standard specifies the determination of total nitrogen content for compound

fertilizers.

This Standard does not apply to compound fertilizers with organic compounds greater

than 7 % (except urea, cyanamide compounds).

2 Normative references

The following standards contain provisions which, through reference in this Standard,

constitute provisions of this Standard. For dated reference, subsequent amendments

to (excluding corrections to), or revisions of, any of these publications do not apply.

However, the parties to agreements based on this Standard are encouraged to

investigate the possibility of applying the most recent editions of the standards. For

undated references, the latest edition of the normative document referred to applies.

GB/T 2441.1 Determination of urea - Part 1. Total nitrogen content

GB/T 8571 Preparation of laboratory samples for compound fertilizers

HG/T 2843 Chemical fertilizer products - Standard volumetric standard reagent and

indicator solutions for chemical analysis

3 Principle

In alkaline medium, USE nitrogen alloy to reduce nitric acid nitrogen, and ammonia is

directly distilled; or in acidic medium, REDUCE the nitrate into ammonium salt, in the

presence of mixed catalyst, DIGEST with concentrated sulfuric acid, CONVERT the

organic nitrogen or amide nitrogen and cyanamide nitrogen into ammonium salt, and

ammonia is distilled from alkaline solution. ABSORB the ammonia in excess sulfuric

acid solution, in the presence of methyl red - methylene blue mixed indicator, USE

sodium hydroxide standard titration solution to back titration.

ADD 300 mL of water to the distillation flask; SHAKE to dissolve the specimen; ADD 3

g of nitrogen and explosion-proof matters to the distillation apparatus.

Except that the sodium hydroxide solution (4.8) added is 100 mL and the specimen

shall be put aside for 10 min before heating during the distillation process, the rest

steps are the same as 6.2.1.2.

100 mL, the rest steps are the same as 6.2.1.2.

120 mL, the rest steps are the same as 6.2.1.2.