Various

[Allan John <allan.john@FORESTRY.GOV.UK>]

Dear All

I have two things to put to the group.

I have read in quite a number of papers over the years of people using an
inert, autoclavable wool like sustance as a support in plant tissue
culture systems.  Does anyone have any details on this substance or
something similar.

I mentioned in a posting sometime before Christmas the standardisation of
hypochlorite solutions.  Quite a few people have asked me how to do this
so I will post the method to the group.

I have been through my experiment records and I can't find the exact
details of concentrations of solutions etc so I will give you the basic
method.  The various concentrations of solution can be found by trial and
error.  To do this I have been back to my school chemistry practical books
and I find that I first did this in September 1966.  Doesn't time fly when
you are having fun.

Take a known volume of the hypochlorite solution and add excess potassium
iodide.  This must be in excess of the amount of chlorine present(5grm?).
Acidify with concentrated acetic acid and make up to a standard volume
(200ml?).  Titrate an aliquot of this solution with standard sodium
thiosulphate until the colour of the released iodine fades.  Add iodine
indicator (I notice we used starch grains in my schooldays) and continue
to titrate until the blue colour disappears.  Average three readings, take
out your slide rule and do the necessary calculations

Best Wishes

Allan John

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