Water for Coffee- Quantifying Dissolved Mineral Content

Water analysis, treatment, and mineral recipes for optimum taste and equipment health.
bobbydukes
Posts: 1
Joined: 8 years ago

#1: Post by bobbydukes »

Hey Everyone,

I wanted to get your thoughts on using a photometer for specific ion measurements, specifically this model here,

http://hannainst.com/hi83200-multiparam ... meter.html

In the book Dashwood and Hendon mention that most methods of measuring ionic concentrations are somewhat flawed in their approach, whether by the use of titrations which are cheap but only offer a very general sense of the full composition, or the expensive route of using spectrometer.

I would like to get anyones thoughts on using this affordable alternative to the spectrometer and whether its at all necessary for dialing in your brewing water?

Much thanks,

GlennV
Posts: 106
Joined: 13 years ago

#2: Post by GlennV »

I would have thought that's a little over the top, and not that much more accurate than the better titration kits. I use the Salifert calcium and alkalinity kits, which use a syringe for the back titration and measure to 10mg/l and 5mg/l respectively. There are magnesium kits, but they're calibrated to the very high concentrations you find in reef tanks, so I just use the API GH kit for Ca + Mg.

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homeburrero
Team HB
Posts: 4858
Joined: 13 years ago

#3: Post by homeburrero »

Agree completely with Glenn. For dialing in the brew water the simple and affordable titration kits are fine. If you want to have an estimate of your [Ca++] vs [Mg++] concentrations you can combine a measure of total/general hardness (GH) with a calcium titration test kit and do a little simple arithmetic.

Here are the conversion factors:
1 mg/L [Ca++] = 2.5 mg/L CaCO3 equivalents
1 mg/L [Mg++] = 4.1 mg/L CaCO3 equivalents

So, for example if you have a total hardness (GH) measure, and also have a [Ca++] ion measure (as is the case with the API Ca++ test kit) then you:

1) Multiply your mg/L [Ca++] value by 2.5 to get your calcium hardness as CaCO3 mg/L.
2) Subtract your calcium hardness from your total hardness (GH) to get your magnesium hardness as CaCO3 mg/L.
3) Divide your magnesium hardness (as CaCO3) by 4.1 to get your [Mg++] ion concentration in mg/L.

While you are at it, be sure to also measure your alkalinity, which in the API test kits is called the KH test kit. Most people buy the GH and KH test kits together. You need the alkalinity measure to help determine whether or not you might have a problem with scale. And it's a good measure of the bicarbonate ion concentration that is discussed in the Dashwood & Hendon book. To convert alkalinity (or KH) to bicarbonate ion concentration, multiply the CaCO3 mg/L by 1.22 to get [HCO3-] mg/L

Note: mg/L and ppm are, for practical purposes here, the same thing.
Pat
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