Calculation of GH- CASO4.2H2O- MGSO4.7H2O

Vijay Saradhi

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Oct 1, 2021
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Hi,

This is regarding reminerlising my 100L tank.
I select CASO4.2H2O for dose to reach target option.
It shows 21g to reach 50ppm which is ok.
But 7 DGH for just 50ppm of only calcium?
Or is Rotala butterfly calculator also adding up 40ppm of sulphur which is shown in the results to calculate DGH?
Attaching screenshot for the same.

Kindly help me on this please.
 

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Allwissend

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Hi Vijay,

The GH (taking into account the more important ions in freshwater Ca and Mg) is calculated using the following formula:
Code:
(mg/L Ca)  * 0.14 + (mg/L Mg) * 0.23 = (°dH GH )

In the present case
Code:
50 * 0.14 = 7 °dH

The sulphate or chloride parts of the salts we add is not measured by GH.
 
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Lmuhlen

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Jan 20, 2021
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Brazil
Confusion with ppm and GH comes from the ppm side. In Rotala and in Allwissend's calculations, Ca ppm means mg of calcium ions per liter, considering the molecular weight of 40 for the calcium ion, while in most tests, they use the unit ppm of CaCO3 equivalent, which means they assume a molecular weight of 100 for each Ca ion (molecular weight of a CaCO3 molecule). It means "what would be the concentration in mass per mass of the calcium molecules if they all were CaCO3 molecules, although they are actually only Ca ions", or "how much CaCO3 I need to add to get this many Ca ions dissolved, assuming they all dissociate".
 
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Vijay Saradhi

New Member
Oct 1, 2021
7
0
1
India
Hi Vijay,

The GH (taking into account the more important ions in freshwater Ca and Mg) is calculated using the following formula:
Code:
(mg/L Ca)  * 0.14 + (mg/L Mg) * 0.23 = (°dH GH )

In the present case
Code:
50 * 0.14 = 7 °dH

The sulphate or chloride parts of the salts we add is not measured by GH.
Thanks mate.. that is really helpful.. I have a better idea now..
 

Vijay Saradhi

New Member
Oct 1, 2021
7
0
1
India
Confusion with ppm and GH comes from the ppm side. In Rotala and in Allwissend's calculations, Ca ppm means mg of calcium ions per liter, considering the molecular weight of 40 for the calcium ion, while in most tests, they use the unit ppm of CaCO3 equivalent, which means they assume a molecular weight of 100 for each Ca ion (molecular weight of a CaCO3 molecule). It means "what would be the concentration in mass per mass of the calcium molecules if they all were CaCO3 molecules, although they are actually only Ca ions", or "how much CaCO3 I need to add to get this many Ca ions dissolved, assuming they all dissociate".
Thankyou for this detailed explanation.. really made me dig deeper.. will learn more about this.. want to check if that calculation works on caso4.2h2o