INDEX/GRADE
SH-90
SH-88
SH-85
CONTENT
90%
88%
85%
Na 2 S 2 O 4
≥90%
≥88%
≥85%
Fe
≤20ppm
Zinc (Zn)
≤1ppm
Other heavy metal
（calculated as Pb）
Water Insolubles
≤0.05%
Shelf Life(month)
12