Sciencemadness Discussion Board

My Calcium Acetate Isopropanol Jelly Failed

xeneficus - 25-7-2016 at 16:31

I somehow managed to mess up what looked like the easiest experiment ever. I had 40g of calcium acetate from eggshells. I had 91% isopropanol alcohol. I saturated 50ml of water with 15g of calcium acetate and poured it into 150ml of isopropanol. I got barely any jelly. I realized that it might be because I'm using 91% isopropanol instead of 99%, so I added more calcium acetate solution. Still nothing. In frustration, I added my entire stock of calcium acetate, ended up with a cloudy mixture. I thought that maybe having too much liquid was the issue, so I filtered off half the mixture, and still nothing. I discarded the result.

So, I just wasted my entire stock of calcium acetate and half my stock of isopropanol. Frustrating, but I'm hoping to find a silver lining in figuring out what went wrong.

CharlieA - 25-7-2016 at 17:50

Just some observations:
1. solubility of calcium acetate (per Wikipedia) is 34.7 g per 100g water at 20 deg C; thus a saturated solution at 20 deg C would be 14.4 g per 50 g water.
2. I assume (usually a mistake!) that you dissolved eggshells in acetic acid (vinegar) to get the calcium acetate. How did you isolates the calcium acetate? Do you have any measure of its purity? (Eggshells are 95+% calcium carbonate.
3. If you thought the presence of water from the isopropanol was the culprit, why did you add additional aqueous solution? At any rate, I wouldn't think using the 91% isopropanol was the culprit, but I haven't tried this reaction myself.
4. I assume (there's that word again!) that you watched NileRed's video where he made the jell. It certainly looked easy.

Good luck with your next attempt.
Charlie

xeneficus - 25-7-2016 at 18:07

Quote: Originally posted by CharlieA  
Just some observations:
1. solubility of calcium acetate (per Wikipedia) is 34.7 g per 100g water at 20 deg C; thus a saturated solution at 20 deg C would be 14.4 g per 50 g water.
2. I assume (usually a mistake!) that you dissolved eggshells in acetic acid (vinegar) to get the calcium acetate. How did you isolates the calcium acetate? Do you have any measure of its purity? (Eggshells are 95+% calcium carbonate.
3. If you thought the presence of water from the isopropanol was the culprit, why did you add additional aqueous solution? At any rate, I wouldn't think using the 91% isopropanol was the culprit, but I haven't tried this reaction myself.
4. I assume (there's that word again!) that you watched NileRed's video where he made the jell. It certainly looked easy.

Good luck with your next attempt.
Charlie

For 1, I wanted to ensure that I saturated the solution so I put more calcium acetate than needed.
For 2, I boiled off the excess water until the calcium acetate crashed out of solution, following Nile Red's video.
For 3, As long as I added saturated solution, the ratio of calcium acetate to water would continue to move towards a solubility equilibrium, even if it didn't reach it.

For my next attempt, I'm going to use hydrated lime (CaOH) to make the calcium acetate to make the process easier and get a purer product. I think I should get my distillation apparatus by then, so I'm going to distill the isopropanol before using it, too. I'll report back then. :)

Artemus Gordon - 26-7-2016 at 17:47

91% isopropanol is the maximum conc. you can get with distillation, so trying to distill it won't gain you anything.

Also, the "California snowballs" experiment uses ethanol, and Sterno is made with ethanol and methanol, so I think using isopropanol is what caused the failure.



[Edited on 27-7-2016 by Artemus Gordon]