found sufficient to yield a working quantity of gas a t an amperage between 0.1 and 0.25. Since polarization causes a slight fluctuation in the current flow we took meter readings a t minute intervals and used the mean. Before starting the actual determination the acidulated water in the apparatus should be saturated with hydrogen by permitting the passage of the current for about fifteen minutes. After this is done, the apparatus is ready for the experiment. After a sufficient quantity of hydrogen has accumulated it is necessary to equalize the pressure in all tubes before a correct reading can be made. This is done by attaching a rubber tube (H) to the oxygen outlet and forcing the water down to the hydrogen level by gently using the breath. When this is done water in the reservoir may be drawn off, as indicated, by means of the siphon (D), if the fact, that the water is slightly acidulated with sulfuric acid is kept in mind. It is best to siphon off slightly more water than necessary and then equalize by carefully adding water from a dropper or pipet. The quantity of hydrogen collected may now be read and the usual corrections for temperature and pressure made, as will be indicated. This value with the average amperage and the time in seconds are the only facts determined experimentally. With these are used the value of the charge on the electron as determined by Millikan in his famous oil-drop experiment (1.591 X 10-I= coulombs), the value of the gram-molecular volume in cubic centimeters (22,400 cc.) and the uumher of atoms in the hydrogen molecule which is two. From this information and with a prayer that whatever errorsthere might be would cancel out, we were consistently able to get results ranging from 5.87 to 6.26 X loz3. Our best readings were 6.04 and 6.08 X loz3. In brief, the Avogadro Number is obtained as follows. The product of the time in seconds and the average amperage gives the number of coulombs required to liberate the corrected volume of hydrogen in cubic centimeters. Dividing the former by the latter and multiplying by 22,400 we obtain thenumber of coulombs it takes to free a gram-molecular volume of the gas. When this figure is divided by the charge on one electron
SPECIAL RESEARCH CONFERENCES OF THE CHEMISTRY SECTION OF THE A. A. A. S. This conference will be held at Gibson Island, Maryland, dming July 10-14, July 17-21, and July 24-28. The meeti?gs will begin at ten o'clock, wlth one or two formal papers outlinmg the fields of research, and directing attention to the unsolved problems. It is advisable to make reservations in advance. For reservations, or further information, write to the secretary, Neil E. Gordon, Central College. Fayette, Missouri. PROGRAM
HENRY GILIAN.Iova State College, General Chairman A. Resinous Polymns, L. ,B?ep?q*uo, Honorary Chairman; H o w a n L. Berrosa, Chairmr July 10. L. H. Backrana, l n r r o r Howard L. Bender, "T particles as to size and LmaapeThomas Midgley, Jr., Leader of diseur3ion of preceding paper -t 7:00 F.W. in honor of L. H. Baekeleland July 11. R. H Kienle. "The Infusible Resinous State'' " " " . u u . . " .u. ."o..x.:>;..S. S Kis tier, .,r.--2;.:--. July 12. S. D. Do ugh$, "The Resinous Vinyl Compounds" I v y AllelI, "Polysty'ene" July 13. C. S. Ma~ruel,.'The Structure of Some Vinyl Polymers" R. B Ea rnes .Speetrosmmand Resin Structure" July 14. G. M. K line.'"~lectronlc Structure and the Behavior of Cellulope C
