Odon Sanchez de lta and I Manuel Urquiza

lnstituto Tecnologico de Monterrey, I A Simple Direct Current Source for the Laboratory Monterrey, Mexico

We have built a simple apparatus for the conversion with a core made of sixteen 31/2-in. iron nails. The of ac to dc which can be made easily and cheaply. choke has the following characteristics: 14 Hys, 300 Similar devices have previously been reported.' I n ma, 60 ohm. It can be replaced by Type C-2308, the present case, the circuit is simple and more stable. Allied Radio (8 Hys, 300 ma, 8 ohm). ~hebresent apparatus could be employed as a source of current in determinations of transference numbers Re by the Hittorf method in which the amount of electricity AC F U+

< -, 9

is measured accurately by a coulometer. The circuitZ Fl and its parts are indicated in the diagram. The choke is made of No. 26 copper enamel wire (13,000 turns)

E D I ~ R ' s NOTE: Probably readers who have had the experi- ence of similar demands on ingenuity to replace funds will be able to contribute to a series of articles on this theme. We solicit only descriptions of instmments proved to be satisfactory by laboratory use. See also THIS JOURNAL, 40,641 (1963); 41s 12. 130, 625 (1964). ' GAwlN, J. E., TalS 38? 36 (lQ6'); BBRNARD, R.r Circuit diagram. F, Standard fuse '1, amps, 250 v max. (Type 0') and

and WOODRIFF, R., -18 JOURNAL, 38,521 (1961). fuse mounting (Type MI. S,Toggle wi tch (Type Dl; Re, (Selenium rectifier a ORR, W. I., "The Radio Handbook," 16th ed., Editors and ,tats 300 (miniature typeli L, choke d; C, and cn, ~ ~ ~ ~ t ~ ~ ~ ~ t i c ~ ~ ~ ~ ~ i -

Engineem, LM., Summerland, Cahf., 1962, p. 694. tor, d u d section, 40-40 pfd, 150 w v (Type 441 5).

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Volume 41, Number 12, December 1964 / 655