Solid content (%)

Temp. (˚C)

Time (h)

Dissolution (%)

SiO2 (%)

Fe

Al2O3

10

70

3

48.9

67.3

98.0

20

70

5

24.1

66.9

97.1

50

70

5

21.4

14.9

96.0

20

70

5

39.7

20.6

97.2

50

70

5

27.7

10.2

96.1

50

70

7

19.3

29.7

97.4

50

25

24

30.2

71.9

96.4