Rochelle Salt – Part II

    Kids, you can make a large single crystal of Rochelle salt and with that make your own piezocrystal-based circuit.  You made your own Rochelle salt granules in the July 2012 ChemShorts edition.  Piezoelectric crystals make very accurate and stable electronic vibrations. Clocks, radios and computers depend on them for precise timing.  The crystal works with other timing elements to produce a stable frequency. Crystals come in a variety of fixed frequencies, from 32,768 to billions of cycles per second. 

    Please note:  All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.

    results in easily grown single crystals. Take the 80 grams or so of granular Rochelle salt that you made earlier this summer and mix it with 100 milliliters of very hot water.

    Filter the solution through a coffee filter, paper towel or filter paper to remove any undissolved material. Allow the solution to sit undisturbed. Small crystals will begin to grow on their own eventually, or you can pour a small amount of solution onto a plate to produce a seed crystal, which may be introduced into a larger volume of solution to grow a large single crystal.

    This will yield amateur piezoelectric crystals. This process is easy and is in fact a simplified replica of how professional piezocrystals are manufactured under carefully controlled conditions, with greater temperatures and ingredients of much greater purity. 

    TIPS:  The recipe can be scaled up to create more solution and larger crystals. 


    Kathleen Carrado Gregar, PhD, Argonne National Labs 
    [email protected]
    September 2012



    A video on making Rochelle salts:

    and testing the crystal:

    This author takes apart a digital watch and uses the piezoelectric crystal near the back of the watch that makes the audible sound for the wrist alarm:
    and in video:
    They use a small LED to see the output from the crystal. You might try the same with your crystal.

    Anne Marie Helmenstine at Chemistry