magix <keicheng at magix.com.sg> wrote in message
news:9hus0l$ha4$1 at violet.singnet.com.sg...
>> 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?
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.