08:46 – Yesterday was the first time in a couple months that we shipped four science kits in one day. So far today, only one, a chemistry kit. We’re getting low stock on those, so we’d better make up another two or three dozen this weekend.
Barbara was surprised when she got home yesterday to find that I’d gone though almost an entire gallon of iced tea. Actually, I’d have finished the pitcher, but I figured I’d better leave a little bit for her. She said there was no way she was going to make a gallon pitcher of iced tea every evening. I told her that the next time we went to Sam’s Club or Costco I’d pick up a can or two of Lipton iced tea mix.
I’m off to make up more chemicals.
12:34 – I was just making up 4 liters each of 0.1M barium nitrate, calcium nitrate, and lead acetate when I realized that I was getting low on all three of those salts. I was going to reorder, but I think I’ll just make them all up right here in the sink. I have a kilo each of RG barium, calcium, and lead carbonates, and plenty of concentrated RG acetic and nitric acids. Add a carbonate to acetic or nitric acid and the carbon dioxide bubbles off, just as it does if you add baking soda to vinegar, and you end up with a solution of the pure acetate or nitrate.
Incidentally, solutions of any of these three salts are an interesting illustration of equilibrium and Le Châtelier’s Principle. Any water exposed to air sucks carbon dioxide from the atmosphere, forming carbonate anions in solution. If you then add a salt whose cation forms very insoluble carbonates (like barium, calcium, lead, or strontium), the carbonates precipitate out. If the solution continues to be exposed to air, it sucks more carbon dioxide out of the air, forming more insoluble carbonates. Eventually, you end up with essentially all of the solvated cations precipitating out as the carbonate salts, leaving almost none in solution.
The best way to deal with this is to boil the water originally to drive off dissolved gases, including carbon dioxide. You then acidify the water with the relevant acid to prevent carbon dioxide from dissolving and forming carbonate anions. The cations stay in solution, although the solution commonly has a slight cloudiness from the tiny amounts of carbonate solids still present as colloidal particles.