A laboratory manual of electrotherapeutics / by William James Herdman and Frank W. Nagler.

  • Herdman, William James.
Date:
[1898], ©1898
Catalogue details

Licence: Public Domain Mark

Credit: A laboratory manual of electrotherapeutics / by William James Herdman and Frank W. Nagler. Source: Wellcome Collection.

Provider: This material has been provided by the Harvey Cushing/John Hay Whitney Medical Library at Yale University, through the Medical Heritage Library. The original may be consulted at the Harvey Cushing/John Hay Whitney Medical Library at Yale University.

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    BATTERY POLARIZATION. (T. 175, ! 7<J.) Construct a Volta cell (T. 166), using plates ij4x3 inches. Use the same plate holder that you used in Exp. 2, being careful that the metallic parts do not touch and thus short circuit '' the cell. Amalgamate only the the lower three-fourths of the zinc to prevent its breaking, and be sure that all metallic connections are bright and tight. Experiment 13.—Connect the terminals of your cell to the A terminals of the galvanometer, having in circuit a resistance of at least 10 ohms. When the needle comes to rest immerse the elements in the dilute acid. Notice that the angle of deflection diminishes rapidly for a time and then more slowly. Allow the cell to continue in action for ten minutes and then jar or brush the gas from the upper plate, noticing the effect on the needle. Repeat, keeping the plates constantly in motion. In each case take the galvanometer reading every half minute and tabulate the results. Experiment 14.—Replace the dilute acid of Exp. 13 by bichromate solution (K2Cr20, + H2 SO+ -+- H2 O). Allow the cell to continue in action ten minutes and then compare the deflections of the needle with those of the preceding experiment. Experiment 15.—Again replace the bichromate solu- tion of Exp. 14 by a solution of copper sulphate (Cu S04). Allow the cell to act ten minutes, take half-minute readings and compare them with those of Exp's 13 and 14.