confused by a simple question on concentration caculation - (Mar/12/2007 )

I am now very perplexed by a simple question of concentration caculation.
I need to make 14% solution of reagent A in PBS buffer. The reagent A are poweders.
So, should I weight 14g reagent A and dissolve it in 100 ml PBS?



Thanks a lot!~

dissolve it with pbs to a final volume of 100 ml.

Dissolve in half the volume, then fill up to 100 mL.

That'll give you 14%w/v concentration, no idea if you need w/v or w/w - they are slightly different.

14% w/w means 14 g of A in 100 g of everything (A+PBS)...
w(A)=m(A)/m(A+PBS)
M.