@ChelsB, I buy mine from
Bulk Apothecary; 8 pounds at a time for $15.84 + $13.52 shipping (if I am not ordering anything else). It totals $29.36 and works out to $3.67/lb. shipped.
It is food grade, so you can use it to experiment with DIY, and I use it for cleaning around the house. It is great in the dishwasher, and I run an (empty) white cycle in the washing machine once every two months (or so); but my favorite use is cleaning toilets.
We have really hard water; and the hard water ring in the toilets are a bear to get rid of. It used to require the use of a pumice stone as bowl cleaners just couldn't get rid of them.
Now, it is as simple as turning off the water to the toilet, flush the toilet to drain the water, fill a mop bucket with roughly 2 gallons of hot tap water and toss in a scant 1/4 cup of citric acid, pour into the toilet bowl (gently; so as not to start the siphoning), and close the lid. I go about cleaning the rest of the bathroom, and in about 15-20 minutes, I return to the toilet. I turn the water back on, let the tank refill, and give it a flush. Everything below the waterline is crystal clean (Use a bowl cleaner for above the waterline). No scrubbing, no rubbing, and no pumice stones required!
I will also make a soupy paste of the CA and water, and apply it with an old toothbrush, to all the hard-water buildup that accumulates around all the faucets, and let it soak for about 5 minutes. Then a quick brush with the toothbrush, and a quick wipe with a clean damp sponge, an the faucets are good to go again.
8 pounds will last me about a year, and I order with my annual PG and VG replenishment (also from BA).
Okay, I'm done being off-topic now (yeah; sure!).
Side note: BA's CA is a bit course for diluting in PG. For my one experiment using it with nic; I put it in a plastic sandwich bag, and crushed it with a rolling pin. The fine powder dissolved much better.