MgSO4.7H2O Magnesium sulfate heptahydrate it also be called epson Salt , sulfate bitter, bitter salt, epsomite Appearance White cylinder crystalline Main content 99.5% min MgSO4 48.59% min MgO 16.24% min Mg 9.8% min PH( 5W/ V% Sol) 5-9 Ferron( Fe) 0.001% max Heavy metal 0.0006% max Lead( Pb) 0.0001% Arsenic( As) 0.0001% max Insoluble 0.001% max Size ( mm) : 0.2-3 1-4