How to Extract Bismuth From Pepto Bismol

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You can use heat to obtain pure bismuth metal from Pepto Bismol.
You can use heat to obtain pure bismuth metal from Pepto Bismol.

It’s easy to extract bismuth from Pepto-Bismol tablets or liquid. Once you have the bismuth, you can grow colorful bismuth crystals.

The active ingredient in Pepto-Bismol is bismuth subsalicylate (C7H5BiO4). Bismuth subsalicylate acts as an antacid, relieving gastrointestinal complaints, such as heartburn, diarrhea, indigestion, and nausea. It’s also antibacterial and anti-inflammatory. There are two ways to separate the bismuth from the subsalicylate portion of the molecule and all the inactive ingredients. One is to burn off the impurities, while the other is to react Pepto-Bismol with acid and precipitate the purified metal.

Bismuth From Pepto Bismol Tablets

Method 1: Purify With Fire

This is what the slag of bismuth oxide looks like when you first get it from Pepto Bismol.
This is what the slag of bismuth oxide looks like when you first get it from Pepto Bismol. (photo: Zaphraud)

You need several Pepto-Bismol pills to get a decent amount of bismuth. Aim for over 100 pills if you want a nice chunk of metal. Each pill contains 262 mg bismuth subsalicylate, but only about 32 mg pure bismuth. But, once you unwrap them all, just blast them with a blow torch to get bismuth slag. Easy peasy.

Method 2: React With Acid

You get higher purity product using acid rather than heat to get bismuth from Pepto-Bismol. You only need a few basic materials:

  • Pepto-Bismol Tablets: Again, you need a lot of them.
  • Muriatic Acid: This is the form of hydrochloric acid (HCl) available from building supply stores. You can use lab-grade HCl if you have it.
  • Aluminum Foil
  • Coffee Filter or Filter Paper
  • Mortar and Pestle: Or, use a spice mill, coffee grinder, or baggie and rolling pin or hammer.
  1. Use the mortar and pestle to crush the pills into a powder. This increases the surface area and makes the reaction with acid more efficient. You’ll probably need to powder the pills in batches.
  2. Dilute the muriatic acid by mixing 1 part acid to 6 parts water. It’s a good idea to wear protective glasses and gloves and work outside or under a fume hood. Muriatic acid is a strong, corrosive acid that can give a nasty chemical burn. Also, make sure your mixing container is glass or plastic, not metal. The acid attacks metals, which is why it’s used in this project.
  3. Dissolve the powdered Pepto-Bismol in the acid solution. Stir it with a wooden spoon (not ever used for cooking again), plastic coffee stirrer, or glass stirring rod.
  4. Filter the mixture through a coffee filter. Use care to avoid spilling or touching the liquid. Save the liquid, because it contains the bismuth.
  5. Drop a piece of aluminum foil into the pink liquid. It will turn black. The black solid is the bismuth. Allow time for precipitated bismuth to fall to the bottom of the container.
  6. Filter out the bismuth by either pouring off the liquid or running it through a paper towel. This time, save the black solid.
  7. Finally, melt the bismuth to finish the purification process. Place the bismuth on a piece of aluminum foil or in a small, empty can and melt it with a torch or over a grill or stove.
  8. Use a toothpick to remove any impurities, which will appear as a skin on the liquid.
  9. When bismuth first cools, it crystallizes into a gray metal. Ideally, beautiful hopper crystals appear! Bismuth quickly oxidizes in air to have a rainbow appearance.

Bismuth From Liquid Pepto Bismol

It’s easier to work with Pepto-Bismol pills, but if all you have is the liquid, you can still extract the bismuth. If you’re using the blow torch method, spread out the liquid to increase surface area and get to work. Alternatively, you could boil off as much liquid as possible before applying the torch. If you’re using the acid method, add it as-is rather than diluting it.

Using Pepto Bismol to Grow Bismuth Crystals

If growing bismuth crystals is your goal, it’s much more cost-effective to start with pure bismuth metal, either ordered online or scavenged from fishing sinkers or ammunition. But, if you’ve gotten this far, crystallizing bismuth is a great way to make a keepsake from your Pepto-Bismol project!

  1. Simply heat the purified bismuth until it melts. One way to do this is to place the metal on a piece of aluminum foil or inside an empty tuna can and blast it with a blow torch. Another method is to heat the metal on top of a grill or stove (not inside cookware used for food). However you melt it, you’ll likely see impurities swirling around the molten metal. Use a toothpick to drag this “skin” away from the bismuth.
  2. Next, you need to let the purified metal cool slowly. If you used a stove or grill, leave the bismuth over the appliance, but turn off the heat. Another method is to pour the molten metal into a second, heated container.
  3. Once the metal starts crystallizing, tilt the container to pour the liquid away from the crystals. You’ll know crystallization is occurring when the bismuth jiggles when disturbed (sort of like metallic gelatin).
  4. Let the metal cool completely before removing it and admiring your work. If you don’t like the appearance, just re-melt it and try again.

Safety and Clean Up

  • Don’t allow children or pets near your project because it involves heat and chemicals. Cats, in particular, are highly sensitive to the salicylate in Pepto Bismol.
  • When you’re finished with the project, sprinkle baking soda (sodium bicarbonate) on your leftover materials until it stops bubbling. Baking soda is a weak base that neutralizes acid. Then, dilute the liquid with a lot of water to wash it down the drain.

Fun Pepto Bismol Facts

Blackening of the tongue and stool is an interesting side effect of taking Pepto Bismol. Sulfur from saliva and intestinal enzymes react with the medicine and form bismuth sulfide, an insoluble black salt. Fortunately, the effect is harmless and only temporary.

References

  • Bierer, D.W. (January–February 1990). “Bismuth subsalicylate: history, chemistry, and safety”. Reviews of Infectious Diseases. Vol. 12 Suppl. 1: S3-S8. doi:10.1093/clinids/12.supplement_1.s3
  • Gray, Theodore. “Gray Matter: Extracting Bismuth from Pepto-Bismol Tablets.” Popular Science. August 29, 2012.
  • Pepto-Bismol. “Why does Pepto-Bismol sometimes darken the tongue/stool and how long does it last?”. Pepto-Bismol FAQ.
  • Wesołowski, M. (1982). “Thermal decomposition of pharmaceutical preparations containing inorganic components.” Microchimica Acta (Vienna) 77(5–6): 451–464.