How to Make Rochelle Salt

Rochelle salt or potassium sodium tartrate is an interesting chemical that is used to grow large single crystals, which are attractive and interesting, but also may be used as transducers in microphones and gramophone pickups. The chemical is used as a food additive to contribute a salty, cooling taste. It is an ingredient in useful chemistry reagents, such as Fehling's solution and Biuret reagent. Unless you work in a lab, you probably don't have this chemical lying around, but you can make it yourself in your own kitchen.

• Cream of Tartar
• Washing Soda or Sodium Carbonate (which you can get by heating baking soda or sodium bicarbonate in a 275°F oven for an hour)

1. Heat a mixture of about 80 grams cream of tartar in 100 milliliters of water to a boil in a saucepan.
2. Slowly stir in sodium carbonate. The solution will bubble after each addition. Continue adding sodium carbonate until no more bubbles form.
3. Chill this solution in the refrigerator. Crystalline Rochelle salt will form on the bottom of the pan.
4. Remove the Rochelle salt. If you redissolve it in a small amount of clean water, you can use this material to grow single crystals.