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Making pH buffers
Posted: 29 Oct 2008, 12:44
by MariaC
Im very!!!!!new at this, I have to make up some pH buffers to calibrate our pH probe, I purchased buffer capsules of pH 4 and 7, the instructiions to make up specify CO2 free water, is my distilled water good enough??? the chem teacher claims its pH is too low but not sure how he confirmed this when the pH probe has never been calibrated!!!! Any feedback would be appreciated. Great site by the way!
Re: Making pH buffers
Posted: 29 Oct 2008, 12:56
by lada
Hi maria, and welcome.
Yes, distilled water is perfect for making pH solutions from tablets. Just make sure you do dilution according to instructions. I use them all the time and they are pretty accurate/
Also to make pH 4 you can use
50mL 0.1M potassium hydrogen phthalate (20.4g / L)
plus 0.4mL 0.1 sodium hydroxide
and make up to 100 mL with distilled water. This should be accurate.
But honestly, I would stick with the capsules.
Lada
Re: Making pH buffers
Posted: 29 Oct 2008, 12:57
by lada
Sorry Maria,
the sodium hydroxide is also 0.1 M