Graham Shepherd muhero.nospam at
Wed Jul 4 16:46:29 EST 2001

magix <keicheng at> wrote in message
news:9hus0l$ha4$1 at
> Hi
> I am having trouble with my experiment (water analysis).
> The method just states "agar" as a solidifying agent and
> we bought Agar Grade A. Somehow, it won't set.
> The author of the method recommended Bacto Agar.
> Is there any difference between these two agars?
> If there are so many solidifying agars (which are not selective) then how
> you go about choosing the right one for your experiment?
> Kei

How much are you using and how hot is your sample? Normally you use between
0.5% and 1.5%. ( 5 - 15 grams per litre). Although you need to heat it to 95
degrees C to get the agar into solution, it won't set until it's cooled to
about 40 degrees C (varies with concentration and the purity of the agar).
If you are using low pH material the agar strength can be reduced.


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