varied by altering the interelectrode distance U> or the electrolyte (e.g., to lap water or distiUed water). The observed variation in I, with electrode separation in tap water and distilled water is given in Figure 7. No dependence of I, on J 0- 9 em) was observed in 3.5% NaCI solution, presumably because its specific resistance (p) is too low (21 n em) fOT ionic migration to be kinetically limiting. In addition to the much smaller galvanic current observed in tap and distilled water relative to that in 3.5% NaCl solution, the current was also independent of electrolyte agitation and time, indicating absence of mass transport controL In distilled water (p = 1.0 X 106 n em) the linear dependence of I Ion the inverse of electrode separation is rationalized as follows. For an ohmically conducting solution,
In this work l!.V. '" 0.823 V in distilled water. The nonlinear variation of 1, with I in tap water indicates that the specific resistance is too low (p '" 1.6 x 1O~ n cm) for ionic migration to be completely rate-determining. Conclusion Through the subject of galvanic corrosion this experiment may be used to expose students to theoretical, experimental, and instrumental aspects of electrochemistry in an integrated, problem-solving context. The experiment has been carried out successfully for several years by senior undergraduate students and participants in a short course on corrosion. literature Cited I. Baboi.La. ft. 1.. EI«tTodw_11icll""l_ ~ H_ _ 1978; pp 73-1'8.
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2. r....-,G.;Ma..mw. r.eo....-... 1t70.26.~ 3. RaacIie. T. H~ KeIlr,P.J.J. a.- Ed... 1$8f. 6/. 121-722-t. &rd.. A. J.; F.. lkner. 1.. ft. El~ ~_Mls aIWl App6t»'-r. ~_y.n.1t8O; pp 135--144. Ii. Rodno.J. Olt.: Reddy. A. K. N. /Ii..". ~ r : r .PIe.."",: X_Yorlpo. 4d1 td~ Wile" N... Yart.. 11179; lIP &-1lo4. 4. Sillltia.S.• Hanna. J. G.: Culmo, R. Anl. C"".... 1961. 33.IlOO. S. Ha"""r, R.; Sip. S.: Ha""a. J. O. Ana~ CM",. 19G3, 37. 600. 6. Kinptan. B H. M.: 030'0Y, J.J.: Hellwig. W. n. ""a~ Ch«",. 1969.41.86. 1. Alla> Ch.omical eomPlUlY. P.O. llo3l U 1. Oalen•. KS, 66139. Aun: Mr. !len Simpaan. 8. N.....D. A. E.: Smith, R. M_ Cntia>/. su.lwl,ry (.......... "'~ PI..,um: New Yo.k, li1i1; VoL 3. p343; Vol. 2. P 144.
Summer Institute on the Mechanics-Materials Linkage The Mechanics-l\laterialsLinkage will be the theme of the Second Annual Summer School of the Institute for Mechanics and Materials at the University of California, San Diego, July 25--August 5, 1994. A group of renowned materials scientisWmeehonicians will provide a coherent set of lecturell nnd laborntory sessions that hove as objectivell: (1)
(2)
To acquaint materials scientists with modern mechllnies applied to mi 268
Journal of Chemical Education
