I was trying to isolate elemental bismuth from pepto bismol (bismuth subsalicylate) using the process seen here but after I added hydrochloric acid, instead of getting a pink foamy substance, I got a white liquid with some white foam. The only reason I can think of, for why this would happen, is that the pepto bismol was expired by a month.

After I realized the reaction didn't work, I added a homemade universal indicator (red cabbage - phenolphthalein - preserved with a little isopropyl alcohol) and started adding sodium hydroxide to neutralise any remaining acid. When I started adding the sodium hydroxide, the solution started heating up and then changed color fairly rapidly from pink to a dull grey green which didn't change when I tried adding more acid.

Shortly after the color change, something started to precipitate out. I filtered off the precipitate and got a clear orange liquid. I then added a little hydrochloric acid to the orange liquid and something immediately started precipitating out. The remaining liquid then turned clear and smells slightly like mint.

My only guess for what I have made is bismuth hydroxide (the first precipitate) but I have no idea what the second precipitate is. Here are pictures of the final precipitates.


2 Answers 2


I'm not sure you did do the experiment wrong. I performed this experiment and it closely matched this video which had a light yellow liquid and foam.

Here are my results

After first filtration

I filtered it a couple more times to remove more foam. Then added the aluminum foil.

After aluminum foil

This is what I got at the end before I filtered the liquid out at the end.

In the end I was able to extract 6.2 grams of bismuth powder from 67 tablets of pepto (a bit less than the theoretical ~10 grams I was hoping to get).


Your second, white precipitate is salicylic acid. You created a solution of sodium salicylate (soluble) when you added the sodium hydroxide; when you added HCl to that, the salicylic acid (relatively insoluble) precipitated, leaving NaCl in solution.

The mint smell is probably due to some esterification between the salicylic acid and the alcohol in your indicator.

As to why your initial attempt failed, I'm still a little unclear on the color of your solution and the amounts used. You describe it first as white and then later as pink. One possibility is that you did not use enough HCl. The foaming that is normally seen is due to some carbonate used as a filler or secondary antacid in the tablets, which reacts with the HCl and will consume some of it.

Would suggest doing the whole thing again, paying careful attention to the initial pulverization and the quantities specified in whatever instructions you have on hand.


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