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what's wrong ?????? a chemistry question......



After reading a lot of posts, i have decided to " adjust" my water chemistry
in order to obtain these results,
which seems to be the right parameters :

    - Ca++ : around 25 ppm ( CaCO3= 60 ppm)
    - Mg++ : around 7 ppm ( MgCO3 = 24,5 ppm )
     - GH : around 4
    - KH : around 4


Here is what i do : my tap water is 1,5 KH ; 2,5 GH , around 16 ppm Ca++,
around 2 ppm Mg ++.

First , the calculus :  -for rising Ca ( adding 10 ppm ) : 10 mg/l ( ppm ) x
160 l = 1600 mg / 0.36= 4444 mg

0.36 being Ca/CaCl2.

KH : using the known recipe : 2 teaspoon of sodium bicarbonate.

- for rising Mg ( adding 8 mg/l) : 5 mg/l x 160 l = 1280 mg / 0.2 = 6400 mg

0.2 being Mg/MgSO4.

- new GH is : 2,5 +( 5 mg/l / 0.2857 ( MgCO3) + 10 mg/l / 0.4 ( CaCO3) )/
17.9 = 4,87

I did a simple and homemade scale ( Harvard ) in order to measure quite
precisely the different chemicals.

Now i test my results :

i put in 1 gal of tap water these : 2 teaspoon of sodium bicarbonate + 4
grams MgSO4 + 4,5 grams CaCl2

Then i take 1 ml of this mixture and add 41 ml of tap water ( 160 l = 42
gal ) in order to test the right concentrations.

Repeating the tests , every parameter is as the calculus except for Mg !!!!!

Mg is TWICE what it should ! Why ???????????

I am using  Lamotte Calcium test and Dupla GH test , The results are :

Lamotte : CaCO3 : 60 mg/l

GH : 6 ( 107,4 mg/l )

So : 107,4 - 60 = 47,4 x .2857 (Mg/MgCO3 ) = 13,54 mg/l Mg !!!!! instead of
8,54 !!!!!

The MgSO4 i am using has no water molecules in it ( not hydrated ), and is
from a chemical products supplier ( ACS grade).


Help me ! i can't sleep !!!!!!!