Convertion of 100% glycerol to 80% - (Jan/09/2012 )

80ML glycerol + 20ML h20!

depends on whether your percentage is based on v/v or w/v or w/w.

v/v, 80ml glycerol, add water to 100ml

w/v, 80gm glycerol, add water to 100ml

w/w, 80gm glycerol, add water to 100gm