"Emir Khatipov" <khatipovNO at NOuchicago.edu> schrieb:
> "D.K." <dk at no.email.thankstospam.net> wrote in message
> news:akufm4$fui$1 at news.doit.wisc.edu...> > ffrank at rz.uni-potsdam.de (Frank =?iso-8859-1?q?F=FCrst?=) wrote:
> > >dk at no.email.thankstospam.net (D.K.) schrieb:
> > >
> > >> I might have a glaring hole in my education but this is first time in
> > >> my life I hear about difficulties measuring pH ~ 1.5 with a properly
> > >> calibrated pH-meter. Is there a problem? What kind? Would you
> > >> similarly say that pH 12 is unreliable?
> > >
> > >At high pH you get an error because the electrode will respond to Na+ or
> > >Li+ (it's called "Alkali-Fehler" in german, "alkali error" or something
> > >like that). But I also have never heard of an error at low pH.
> >
> > Yes, this effect is easy to understand. Although I doubt it is significant
> > at pH 12 - IIRC, most electrodes' specs claim linear response to 12.
> >
> > DK
>> Don't get so emotional, Dima! I was just trying to get the point about the
> accuracy knowing how most people in molbio labs would calibrate pH meters -
> by one buffer (pH 7) !. I also noticed that most labs buy less expensive pH
> meters that cannot be easily calibrated over the whole pH range. For
> example, if you calibrate the instrument with buffers pH 7 and pH 4 and then
> check the reading of the buffer pH 10, you would not get the correct reading
> of 10.
Ah, that's what it's all about. O.K.
We are using buffers of pH 2 and 4, pH 4 an 7, and pH 7 and 10, and
everybody writes down in which region he or she has calibrated. So I
guess I'm on the safe side even at pH 1.9 or 1.8
Bye, Frank
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