CHEMICAL INDUSTRIES EXPOSITION Grand Central Palace, New York, Sept. 20-27 The Annual Chemical Show is a great opportunity for the teacher of science to see what progress has been made during the preceding year in the industrial and laboratory arts. Each exhibitor makes a special effort at this time to show his accomplishments in the way of newly developed apparatus. Although the exhibits have a particular bearing on chemical industry, among the processes that are shown and the apparatus and instruments that are demonstrated, there is hardly a single process or instrument that does not involve a physical method or a physical measurement. The Show is a demonstration of the very close relation between Chemistry and Physics. We are sure that those readers of Science who find it possible to attend will be particularly interested in Leeds and Northrup Company's exhibit, in Booth 55, Main Floor. Our advertising during the past year has persistently pointed out the possibilities of applying Electrical Measuring Instruments to Chemical Processes. Some of these applications are industrial, others have more to do with laboratory technique. Many of the newly developed instruments will be shown in operation. Among other things, there will be: A Bovie Hydrogen Ion Potentiometer, which semi-automatically plots an acid-base titration curve on paper that directly gives the hydrogen ion concentration at any point on the curve. A Type K Potentiometer Outfit with Clark Hydrogen Electrode, mounted on a stand with motor-driven shaking device. A Portable Hydrogen Ion Potentiometer that is especially suitable for biological and water survey work. A cordial invitation is extended to you to visit our booth LEEDS & NORTHRUP COMPANY ELECTRICAL MEASURING INSTRUMENTS 4901 STENTON AVENUE PHILADELPHIA, PA. The Butterflies of Eastern United States and Canada By SAMUEL H. SCUDDER Three volumes, quarto, with 89 plates (18 colored), 4 maps, 3 portraits, and 1958 pages of text THIS HIS great work is still the standard authority on North American Butterflies. It should be in every important American library, and in all entomological libraries of the entire world. A limited number of sets, newly bound in buckram, three volumes, are offered for sale by Mr. Sherman, at the greatly reduced price of TWENTY-FIVE DOLLARS (The subscription price was Seventy-Five Dollars) The Butterflies of North America By WILLIAM H. EDWARDS Superb set of this very rare work, three series complete, with 152 hand-colored plates Price on application The Natural History of the rarer Lepidopterous Insects of Georgia By JOHN ABBOTT and J. E. SMITH The great folio of 1797, with 104 hand-colored plates MANY OTHER FINE ENTOMOLOGICAL WORKS ON HAND Send for Catalogues 7 and 8 (100 and 110 pages, respectively) "BOOKS ON INSECTS" JOHN D. SHERMAN, JR., 132 PRIMROSE AVENUE, MOUNT VERNON, N. Y. GEN-EL-ITE is a product of the General Electric Company's Research Laboratory. The many cases where oil lubricated bearings are objectionable led to investigation of the lubricating properties of metals. Gen-el-ite was the result. Difficulties of lubrication, objectionable to oil itself and the comparatively high temperatures to which the bearings may be subjected were the foundation of the necessity satisfied by the Research Laboratory. Gen-el-ite is pressed to shape. For further details write the Schenectady (N. Y.) office. Owing to the nature of Gen-el-ite, the various applications must be individually considered. DIFCO Dehydrated Culture Media ACCURACY is the goal of all work in bacteriology, as well as in SPEED is greatly desired in bacteriological procedure and no ad- CONVENIENCE becomes a prime consideration when accuracy and speed are at stake. The convenience of "Difco" Culture ECONOMY is a consideration when quality has been satisfied. More than a dozen standard formulae, all carried in stock by Your inquiries are solicited DIGESTIVE FERMENTS COMPANY DETROIT, MICHIGAN, U. S. A. 268. Student's Model Analytical Balance. This is an analytical balance of simplified design, of full size; the materials, the workmanship and the finish of this balance are the same as the more expensive balances. Case-Solid mahogany, finished and rubbed; 17" wide, 16" high, 9" deep, counterpoised door. Beam-Aluminum, truss type, 6" long, finished in black with 50 divisions on each side of the center (a great convenience in weighing). Balance screws on each end. Bearings-All edges and bearings of agate. Dial-Graduations are red on white background so that black pointer is easily observed. This balance has a brass column, a circular universal level, a double rider carrier, adjustable leveling feet and a pan arrest independent of the beam release. -In Stock for Prompt Delivery Price, $65.00 SCIENTIFIC MATERIALS COMPANY PITTSBURGH, PA. |