VOL. 7, NO. t)
EXPERIMENTS I N CRYSTALLIZATION
2171
tin band. Tear some cotton cloth into narrow strips and wind the strips around the wire and band so that all of the metal is completely covered. Wet all of the cloth and suspend the crown so prepared in a solution of potassium dichromate till the cloth is well penetrated by the liquid, remove, and let dry; small crystals of the salt will form in the cloth to serve as "seed" for the later process. Prepare a sntzlrated solution of potassium dichromate in 500 cc. water heated to about 80 degrees; the solution must be fully saturated a t that temperature, and should be perfectly clear. Suspend the crown, top down, in the hot liquid and let it remain there over night. In the morning the crown will be found covered with bright red crystals following the lines of the wires and the band. Remove and let dry in a cool place. A lining of green velvet or other material may be made and a ribbon tied around the outside of the band. Nicely arranged in this way any student may well be proud of his work. Should the crystals become slightly dulled with the passage of time, they may be brightened by dipping them into acetic acid for a moment and then setting the crown in a cool place to dry.
"The Story of Nitrocellulose," a New Motion Picture. "The Story of Nitrocellulose" is the name of the latest motion picture produced by Hercules Powder Company, Wilmington, Del., for general distributioll. The film, three reels in length, depicts the sources, manufacture, and uses of nitrocellulose, the versatile product which is the basis of modem lacquer, celluloid, and pyroxylin materials. The early part of thc film shows the source of the raw material-the cotton fields of the South-and shows the purification of the cellulose (cotton linten) a t the Hercules plant near Hopewell, Va. The succeeding scenes of the Hercules plant a t Gillespie, New Jersey, illustrate the nitration of cellulose and the purification and subsequent testing of thc product. Chemical and mechanical processes in the production of nitrocellulose are well illustrated by photographs and animated drawings Chcmical control to assure uniform high quality is a n important element in the manufacturing process. The important part which nitrocellulose takes in present-day civilization is visualiiicd by showing the divcrsified products of which i t is an ingredient. The film was made for Hercules by The Pathescape Company of America. "The Story of Nitrocellulose" is available in standard or small-sizc film by application to the Visual Education Department, Hcrculcs Powder Company, Wilmington, Delaware.
Progress Exposition in 1933. A "Century of Progress Exposition" will hc held in Chicago in 1933, and all countries are invited to participate. The exposition will picturc all advances in progress which have been made in the last hundred years. The organization of the scientific section is in the hands of the ITnited States National Research Council. Dr. A. D. Little, er-president of thc Society of Chcmical Industry, is chairman of the sub-committee on chemistrv, and Dr. C. G. Pink chairman of that on electrochemistry.-Chenz. Age
