Item

Premium product

First-class product

qualified product

appearance

White crystalline or granular product

Mass fraction of nitrogen (on a dry basis)/% ≥

25.4

24.5

23.5

Water mass fraction a/% ≤

0.5

1.0

8.5

Mass fraction of sodium salt b（Na）/% ≤

0.8

1.2

1.6

granularity c（2.00mm～4.75mm particle）/% ≥

90

80

—

Average crushing resistance of particles c/N ≥

10

10

—

Mass fraction of arsenic and its compounds（As）/% ≤

0.0050

Mass fraction of cadmium and its compounds（Cd）/% ≤

0.0010

Mass fraction of lead and its compounds（Pb）/% ≤

0.0200

Mass fraction of chromium and its compounds（Cr）/% ≤

0.0500

Mass fraction of mercury and its compounds（Hg）/% ≤

0.0005

a. The mass fraction of water is the result of factory inspection.

b. The mass fraction of sodium salt is calculated on a dry basis.
c. Crystalline products have no requirements for particle size or average crushing strength of particles, while granular products must at least meet the requirements for first-class products.