Required Practical - Analysis and Purification of Water Samples

Thanks George, will look into Reverse Osmosis (sounds expensive?) but in the meantime will pass on that info to the teacher concerned. Sorry for late reply but rarely get to sit down at the computer lately :confused: Lucky you Emil! :D
I have to conceed Emil - the weak positive I got was probably down to contamination of the Glassware. So no need to invest in the expensive Reverse Osmosis kit Katheleen @Kathleen H. :);)

Do you clean your still with HCl? Even if properly rinsed you may still have residual chloride that can cross over. I clean mine with formic acid but I know some stills can be cleaned with HCl...
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Hi Emil, yes I use formic acid too, just not often enough! :rolleyes: The heating element is quite corroded, maybe that doesn't help? Never mind, for demonstrating 'purity' of water we'll recommend conductivity ;)
Btw I most definitely cheat with pH specific samples. Comparing strong/weak acids at KS3 for example. UI does not show any difference between them at equal concentrations.
Finally getting round to this practical for real.. teachers had old version so will demo presence (or not) of Na and Cl ions as a demo. Has the desiccated cobalt chloride paper as new protocol asks for, though how water v salt water can be compared with that is anyone's guess.
And yes.. there was a definite difference even just on universal indicator paper between deionised and tap/drinking fountain water..
Our Chemistry teacher used the cobalt chloride paper to show that there was water present in both the salt water and the distilled water. This showed that the cobalt chloride paper indicated the presence of water, but was not a suitable indicator of whether the water was potable. She used it to highlight that indicators are not necessarily useful in all situations.