Question about titration

I’ve been learning how to use the titration kit from Red Sea to measure kH, Mg and Ca and theres one thing I wanted to check to see if it makes sense:

Instructions tell me to use only 2ml of sampled water when titrating for Mg. It should start at red before being titrated and end at blue after. Problem is it never gets to red, leaving me to assume that Mg isn’t easily measurable in such a small sample.

Has anyone tried scaling up, i.e. measuring with a bigger sample for higher accuracy?

Its a resolution issue imo.

We only ever get a result of 1drop of the final indicator solution. So 0.01ml, which is 20ppm +/-20

It seems that MG is not all that commom in fresh water, and these kits are designed for salt water, hence the issues we have.

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Hey there, are you sure you’ve got the right colours here? Mg titration using this kit should start with the solution being a dark purple, then change to a deep blue. Most water sources outside RO with remin should turn blue relatively quickly, in say 1 or 2 drops — there usually isn’t all that much magnesium to unbind in most naturally occurring water sources.

If you haven’t already, check out Christopher Hendon’s walkthrough here:

I found this really useful! :slight_smile:

Yeah, I found the video from Chris very helpful. I realised that his sample did reach a red color like in the instructions because the magnesium in his water turned out to be pretty high. It only reached a purple color when I titrated, only one or two drops from end point, like you said.

When redoing, I tried doing exactly the same, but using 4ml water instead of 2ml, and adding 10 drops of each liquid instead of 5 before titrating. The thought being that the each drop during the final step would only have 50% effect, giving a more accurate result.

Does it make sense?