Exercise 113. Lead Iodide Crystals

In the manner described in the preceding exercises, prepare a gel of equal parts of sodium silicate (density, 1.06) and 1-normal acetic acid, adding 2 cc. of normal lead acetate for every 25 cc. of the mixture. Prepare the gel in half-filled test tubes and when it has set add to each tube a layer of a solution of 2-normal potassium iodide. A compact layer of lead iodide gradually forms just below the surface of the gel, followed by growths of fernlike and hexagonal crystals. 

Additional Exercises Crystals of silver sulfate, silver chromate, calcium tartrate, and copper tartrate. 

---