Re: [CH] PH Testing - Buffers
- To: q*@erols.com
- Subject: Re: [CH] PH Testing - Buffers
- From: H* E* P*
- Date: Thu, 18 Mar 1999 13:58:07 -0800
- References:
quark@erols.com wrote:
>
> "Harold Eddleman Ph.D." wrote:
>
> > <snips>
> > I calibrated with NBS buffers every day. Those will cost you $20 per year.
>
> I have some tropical aquariums (African Cichlids) that I keep at about 7.8 -
> 8.1 PH.
> Currently, I'm using Spa test strips.
>
> However, I bought a "pHTestr" from Edmund Scientific that looks like it might
> do the job for the home hobbyist -- but it does need a buffer solution to
> calibrate against.
>
> Can I make my own from common chemicals (e.g. NaHCO3) ?
> I can measure grams & have graduated cylinders, but not any titration
> equipment.
> Ideally, I would like if the buffer was somewhere 7.0 to 8.4 region.
>
> Also, can a hobbiest get NBS bufferes ?
>
You can buy pint bottles of buffer for about $10 from Fisher etc.
Shipping may be more than the buffer. You may find a local supplier, the
local sewage treatment plant may know a local supplier.
I buy the pHydrion powders and add these to distilled water. I guess
the powder bags are good for decades.
You really need two buffers to bracket the region of interest. pH 4,
7, 10 are commonly used. You would want 7 and 10. Using the pH 7
buffer, put electrodes in it, adjust meter to 7. rinse electrode off,
most use distilled water but tap is fine, then insert electrodes in pH
10 and adjust the second knob to so meter reads pH 10. If you have a
good meter it will remain stable pretty much the whole day. Mine often
stays in calibration for weeks even when turned off.
NBS means they calibrated the buffer in accordance with National
Bureau of standards.
If you have the Sorensen phosphates, you can weigh out and make your
own buffers. Biochemists did that for decades before private companies
began selling the premixed powders.
You can get by with a pH buffer of pH=8. made by:
to 50 ml of 0.2 Molar boric acid in 0.2 M KCL add 3.97 ml of 0.2 Normal
NaOH and dilute to 200 ml.
Just adjust your acquarium water using this buffer std and you will be
at pH 8. However, if the meter reads 7.0, it may not be 7.0. You must
use 2 buffers if you want to set the slope of the meter so you can read
any pH.
Buffers are rated at one year or more, but would be close after that.
It mainly depends on how much carbon dioxide has been absorbed from the
air.
If you need more info, write again. There may be web sites on
pH--should be. My WWBBS site has a bit for kids. I never did finish it.
Someday I will have more on pH for kids, farmers, and amateurs.
I measure soil pH by placing soil in a clean glass (or beaker) and
adding just enough water to make a gravy and let stand a few hours or
overnight. Then carefully insert the elctrode(s) into the gravy and read
during gentle movement. Caution: do not break the thin electrode against
a rock.
>
> Thanks for any info.
>
> Andy Barnhart
--
Harold Eddleman Ph.D. Microbiologist. i*@disknet.com
Location: Palmyra IN USA; 36 kilometers west of Louisville, Kentucky
http://www.disknet.com/indiana_biolab = Agriculture, science projects
and info for amateurs, gardeners, farmers, teachers, kids
http://wwbbs.otherside.com/PUBLIC/HOMEPAGE/haroldeddleman_303/INDEX.HTM
Home Science Projects: fun for parent and child, Computer programs
http://ibl.webjump.com/ger.htm <== Simple german for beginners.
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