equarius: Sodium Sulfate ehh? If Magnesium Sulfate from Epson Salts isn't good enuf and for some reason Calcium Sulfate from Drierite isn't good enuf then just make your own Sodium Sulfate from your OTC reagents!
Of course you'd want to be careful about it and use dilute solutions but, if you have a good scale, just react the sulfuric acid with the sodium hydroxide.
WARNING: This will be a violent reaction. Strong Acid + Strong Base = !!!
Anyway, you definately want to use an accurate scale so you can get the right amount of each because an excess of either could be a problem.
You would also want to use dilute solutions in water to minimize the risks. Becareful even making the solutions. Both release heat when dissolved in water, the acid especially, so do it slowly. Trust me, the last thing you want in your work area is hot acid! Always add acid to water and not water to acid. That is important!
But there better ways to get sodium sulfate. A nice one would be to use NaOH and CuSO4.5H2O from root killer. Two pounds of 99% CuSO4.5H20 cost $7 at Home Depot. Look near the sulfuric drain opener. Cu(OH)2 is pretty much insoluable in water so to do the rxn weigh out 25g of Root Killer and put it in 400ml of distilled water. It won't dissolve very fast so let it sit while you measure out 4g of Lye and dissolve it in 100ml distilled water. Remember that you wanna use a plastic or wooden (non metal) spoon for both the lye and the root killer. And don't leave the lid off the lye for long because it soaks up water from the air throwing off all subsequent weight measurements, not to mention it gets clumpy...
Anyway, you'll probably have to stir the water/copperSulfate mix quite a bit to get it all dissolved. Resist the urge to add more water and you'll have less water to get rid of later. After a few minutes the pretty blue crystals will be totally dissolved and the water will look like Windex. Now dump the NaOH solution in and stir. Instantly the solution will change from clear to opaque. Stir it a little more and then set it aside. After maybe 20 minutes or so the solids will begin to settle to the bottom. Depending on the shape of your reaction vessel (jar) you probably have about an inch of clear liquid above the opaque suspension. If the liquid is still blue then there is still some copper sulfate in the water. Make some more lye solution and use an eyedropper to add a little bit at a time. More cloudy precipitate will form so give it a few minutes to settle in between additions of lye. All of the copper sulfate is out of the water when the overhead looses its blue color and looks like plain water. You gotta be careful hear because it is easy to over-shoot and add too much NaOH.
Now all you have to do is break out the filter paper and remove the Copper Hydroxide. Its a pain in the ass but you can handle it. Once you get it clear, I suggest letting it sit for a day or so to see if anything else precipitates out...
Evaporate the water and you've got your Sodium Sulfate. Each molecule of Na2SO4 can hold 10 molecules of water. "Wet" sodium sulfate melts at around 33C but it looses water when it get to 100C and turns back into a solid... Of course as before you evaporate it the first time it will be dissolved in water so you wont notice this effect...
Also, sodium sulfate can be formed by the reaction of sulfuric acid with table salt. The bad thing about this route is that it release HCl gas which you really don't want to breath... Incidentally, this is the common home method of producing HCl to bubble through certain freebase/solvent solutions to yield dry salt. So I guess you could consider it a useful byproduct. I bet that in most cases of home HCl gas generation that there is still a bunch of table salt mixed in, along with either aqueous HCl or sulfuric acid or both. This is a pretty piss-poor way to do it if all you want is the NaSO4....