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.

    23/192 (page 11)
    Experiment 16.—Attach the terminals of Volta's pile to the A terminals of the galvanometer and let the time, resistance and observation be the same as in the pre- ceding experiments. Do the deflections vary ? Why? The Volta's pile should be taken apart and the plates cleaned and dried as soon as possible after using it to avoid corrosion of the plates. Experiment 17.—Examine the Daniell's cell* on the side-table. Test it as to its polarization in the same way as you did the cells in the preceding experiments. (T. 181). Experiment 18.—Test Bunsen's cell* as you did the Daniell's and examine the Grove's cell. (T. 182, 183). Experiment 19.—Determine the constancy of the Leclanch6 cell, having it connected up for ten minutes. Record the readings every half minute. Now allow the cell to stand on open circuit for a minute and then close the circuit only long enough to take the reading the instant the needle stops oscillating. Continue this for ten minutes keeping the circuit closed as short a time as possible. Do the results indicate a recovery in the strength of current? If so, to what is it due? (T. 184). Because of the time required for the needle to come to rest it will be quite as instructive to compare the first swings of the needle in the later part of this experiment. It is found that the current from the voltaic cell rap- idly diminishes in intensity, so that in a short time the ac- tivity of the cell is very much reduced or may cease alto- gether. This may be due to several causes, the chief of which is the collection of hydrogen on the copper plate, thus causing the polarization of the cell. From Ohm's law (see page 22),it is apparent that any- * Note, Specimens of these cells will be found on the side table.