# How do I measure the density of a cellulose acetate membrane?

I've been playing around with filtration methods, and got my hands on a casting machine for this purpose.

My first mission was to find out how porosity can affect filtration. To see this for myself, I just ran some titratable solvent through the membrane I produced, and analyzed the difference in concentration.

Looking through some textbooks, I found a neat formula for calculating porosity, but there's one thing that's been bugging me. The formula requires the density of the membrane.

This isn't something that I can just use the Archimedes Principle to get. I need to look at the wet weight and dry weight of the membrane or whatever.

My dilemma right now is I can't find a single resource that lets me measure the density of a membrane without requiring either some pricey machine or extremely esoteric methods that's beyond my abilities. I'm really at a loss right now for this particular method.

There's this equipment here that's usable, but that looks like one high-end son of a gun. I really don't want to throw any more money than I already have.

How do I measure the density of a membrane with tools available in the home?

• Why can't you use Archimedes' Principle (by that I assume you meant measuring volume by displacement)? Can you elaborate on why you need the wet and dry weight? Commented Jul 24, 2014 at 17:25
• The film pores are in sizes of microns. Putting the film in water just like that will give a horrendously inaccurate result. Also, uh, the formula needs it. The wet weight is basically the weight of the membrane after you use some water to remove it from the plate. The dry weight is when it's...dry. The difference of the weight gives you how much water is occupied by the pores. Commented Jul 24, 2014 at 18:22
• Can you post the formula and its source? There seems to be some information missing here. Commented Jul 24, 2014 at 19:00