Chemistry - Help!

[MAF]

Chemistry was never my strong point, but as our estate has its own source of water and so there’s no County Council data available, I thought I’d have a go at testing it myself, see what kind of water I use for brewing.

Got two aquarium test kits – one for Calcium and the other for General Hardness.
The GH test measured 12dH which converts to 214.8 mg/L (CaCO3) according to this calculator http://www.hagen.com/uk/aquatic/ghkhconvcalaction.cfm
The Calcium test gave a level of 140 mg/L Ca2+.

Now where I get confused….
The Calcium test booklet has formulas to determine the ratio between Calcium and Magnesium:
Calcium Hardness = Calcium x 2.5
General Hardness – Calcium Hardness = Magnesium Hardness
Magnesium Hardness / 4.1 = Magnesium mg/L

So if I put in my figures:
Calcium Hardness = 140 x 2.5 = 350 mg/L
Magnesium Hardness = 214.8 – 350 = -135.2
Magnesium = -135.2 / 4.1 = -32.98 mg/L

Have I gone totally wrong here, the negative answer for Magnesium seems incorrect?

[gnutz2]

Well thats confusing me allright, all i can add is that i sent a bottle of water to Murphy and Son in notingham and they sent back a full water report.

Cant see postage being that much from ireland

Water report is from here http://www.murphyhomebrew.com/laborator ... at_27.html

HTH

[fisherman]

Hello,
I think what you need is a Salifert Alkalinity test kit from e-bay, When you find your alkalinity it should be game over. No problem.
Look at the Brupacks site " water treatment information " and read about DLS and CRS.
Good luck

[MAF]

gnutz2, sounds like a great service, thanks for the link. One of the main reasons I wanted to figure it out meself though, was so that I could do it at different times to see if there's any variance.

fisherman, that Brupaks information page really helps breaks it down simply, thanks for that. Looks like I should've got a kH test kit rather than the General Hardness one. Think I'm starting to get me head around it