Lead Acetate Counterstain?

[Philip Fortgens]

Hello All

I am trying to make up a Lead Acetate counterstain (by the method of 
Millonig, 1961) for EM use.
Im am doing the following:
1)	Mix 20g NaOH + 1g NaKTartrate to 50ml with H2O
2)	Make 20% aq. PbAc
3)	Mix 5ml PbAc soln + 1ml Soln (1) above 
4)	Water is ultrapure (Millipore Alpha plus), and de-gassed by boiling.
 
I am having problems with the reagent because I get a flocculent white ppt 
at step 3, which doesn't seem right. I cannot get rid of this ppt. Is this 
a problem (i.e. is the reagent SUPPOSED to do this)? Do I need to make up 
the reagent some other way (e.g. at midnight when the moon is full)? Should 
the ppt be filtered off? HELP!

Many thanks in advance for any advice

Philip Fortgens
Biochemistry Dept
University of Natal
Pietermaritzburg
South Africa