LEAD TREE.
(ARBOR SATURNII) *
I t is well known that a metal can be displaced from a solution of its salt by the action of a more active metal. Thus, copper displaces silver, lead displaces copper, and zinc displaces lead from water solution of the acetates or nitrates of silver, copper, and lead. These different displace-
ments can be shown nicely by the preparation of "trees." In the case of the displacement of copper by lead, it is advisable not to use a solution of
* The work of preparing and photographing this lead tree was done by Gaffer,Gavin, and Robbins, students at the English High School. After three weeks, the filaments of lead are about twelve inches long.
either the sulfate or chloride of copper since the lead salt formed in each case is insufficiently soluble. It is possible, by pursuing the following procedure, to prepare a lead tree of much more than the usual attractiveness. Prepare a 3% solution of lead acetate in distilled water to which a few drops of acetic acid are added. Filter the solution into a tall narrow jar; a 250-cc. graduate answers admirably. The liquid should rise to within about an inch of the top of the jar. Select a cork stopper which fits snugly into the top of the jar and bore a small hole in its center. Choose a round battery zinc rod and saw i t into two parts of equal length. Pass a non-tapering screw through a metal washer, then through the cork, and screwit firmly into the zinc rod a t the end already carrying a threaded hole. Wrap the zinc rod tightly with a layer of asbestos paper and tie the paper firmly in place; the entire length of the zinc should be covered. Insert the cork into the top of the jar so that the zinc hangs vertically in the center of the liquid, not touching the side of the jar. The liquid should not rise to touchthe cork. Set aside for several days. .The asbestos paper slows down the displacement so that the "tree" forms very slowly. After several days long feathery streamers of lead will form, growing slowly down and reaching eventually to the bottom of the jar. In the specimen recently prepared by the writer these streamers developed in about a week and are some six or eight inches in length and p~esent a beautiftil appearance. It is, perhaps, unnecessary to say that the jar should not be handled or camed about more than necessary since the lead streamers are easily dislodged.
