Testing Hardness (1 Viewer)

[ND]

Which test(s) can you do (in school) to get a quantitative value for water hardness?

 

[s2ophie]

we did a titration with erichrome T (i think that is what its called)

 

[ND]

Is that a solution or an indicator?

edit: nevermind, found some info on it, thanks.

 

[abdooooo!!!]

We determined whether a sample of water was hard or soft by adding drops of a soap solution (one at a time) to 50 mL of the water sample in a small flask and shaking it after each addition and noting the number of drops needed to produce a good lather (froth). We did the same test on 50 mL distilled water. If the sample required several more drops than distilled water did, then the water was hard: if it required about the same number of drops, then the water was soft.
OR
We determined whether a sample of water was hard or soft by taking 50 mL of it, adding an ammonia, ammonium ion buffer and a few drops of Eriochrome black indicator to it then titrating it with 0.010 mol/L EDTA solution. The endpoint was when the indicator changed colour from purple to blue (loss of the last tinge of red). We treated 50 mL distilled in a similar way. If the sample to be tested required a significantly larger volume of EDTA than the distilled water did, then the sample was hard.

conq chem website answer for question 26 in 2002 hsc exam

 

[ND]

Originally posted by abdooooo!!!
If the sample to be tested required a significantly larger volume of EDTA than the distilled water did, then the sample was hard.

Ah so we don't have to perform calculations with that crazy EDTA thing, phew.