Calcium Sulphate translate to GH?

[Jon_Shen]

Hi guys, any idea how much ppm of calcium sulphate gives 1 dgh?

[juggler]

From http://faq.thekrib.com/intro-tables.html, I believe it's the same as 17.8ppm even for CaSO4.

[Jon_Shen]

So are there any adverse effects in slightly overdosing calcium other than affecting Kh/Ph/Gh? I just want to make sure that my calcium would be comparatively higher so that i could dose my potassium/Mg without much worries.

[theodore]

By definition 1dgh = 10mg/L CaO
Atomic Weight Ca= 40 O=16 CaO= 56
Therefore, 10 mg/L CaO contains 40/56 * 10 = 7.143 mg/L of Ca

For CaCO3,
Atomic weight CaCO3=100
So 7.143 mg/L of elemental Ca in CaCO3 =>
100/40 * 7.143 = 17.8575 mg/L of CaCO3

Calcium Sulphate exists in at least 2 forms according to some Chemistry websites I've visited :

For CaSO4,
Atomic weight CaSO4=136
So 7.143 mg/L of elemental Ca in CaSO4 =>
136/40 * 7.143 = 24.2862 mg/L of CaSO4

For CaSO4.2(H20),
Atomic weight CaSO4.2(H20)=172
So 7.143 mg/L of elemental Ca in CaSO4.2(H20) =>
172/40 * 7.143 = 30.7149 mg/L of CaSO4.2(H20)

1 dgh = 17.8575 ppm CaCO3 or 24.2862 ppm CaSO4 or 30.7149 ppm CaSO4.2(H20)

[Jon_Shen]

Thanks theodore,i've been wanting to know about calculating atomic weightage.Good stuff.By the way do you know where i could get calcium sulphate dihydrate?