ITEM	Best Quality (Ion-membrane Process)	First Quality (Diaphragm Elec-Process)
Sodium Hydroxide %≥	99.5	96.0
Sodium Carbonate%≤	0.5	0.8
Sodium Chloride %≤	0.05	0.05
Ferroso-ferric Oxide ≤	0.004	0.005
Silicon Dioxide %≤	0.004	0.006
Sodium Sulfate %≤	0.050	0.070
Copper %≤	0.0002	0.0005
Calcium %≤	0.005	0.008