|
Item
|
Index
|
||
|
Top grade
|
First grade
|
Qualified product
|
|
|
Appearance
|
white scaly or crystalline powder
|
white scaly or crystalline powder with slight colors
|
|
|
molten Chroma(Chroma no. )≤
|
20
|
50
|
100
|
|
thermostable Chroma(Chroma no. )≤
|
50
|
150
|
-
|
|
Chroma of vitriol(Chroma no. )≤
|
60
|
100
|
150
|
|
crystallization point°C≥
|
130.5
|
130.3
|
130.0
|
|
Purity(mass fraction)%≥
|
99.50
|
99.50
|
99.00
|
|
Free acid(mass fraction)≤ %
|
0.20
|
0.30
|
0.50
|
|
Ash(mass fraction)%≤
|
0.05
|
-
|
|
