Question

how would you make a 4% percent paraformaldehyde solution?


Work:
starting from 20% (diluted with PBS)
V1C1=V2C2
(100)(20)=(x)(4)
x=500
so add
496 ml of PBS (accounting for 4% paraformaldehyde) or would you add 500ml of PBS

Thank you

Answer 1

It depends on whether the percent is w/v or v/v.

if it is v/v, as I suspect, you are diluting the original by a factor of five, so add 4 parts water.

if you want 500 ml, add 100ml of 20 percent, and add 400ml water.

if you want 45ml, add 1 part of PBS (9ml) and four parts (36ml) water.