fi
=
I+ 1 2 Xk ( A U ) j -
k=
k+ 2
2
('436)
In Equation A36, AU is the change in value of the surface concentration of U between the ( j 1)th and the jth time intervals. ( A U ) j = U l , j + 1 - U1,j (A37) W, = 1 2A (A39
+
by solution of Equation A48. Gaussian elimination efficiently solves Equation A48 because is nearly tridiagonal. RECEIVED for review October 31, 1968. Accepted February 7, 1969. Work supported by the United States Department of the Interior, Office of Saline Water.
+
Xz
=
2 --(2A 3
+ B2)
('441)
Correct ion Generalized Numerical Method for Stationary Electrode Polarography: Application to Reactions Involving Second-Order Homogeneous Chemical Complications In this article by Glenn L. Booman and Dallas T. Pence [ANAL.CHEM.,37, 1366 (1965)], the following errors appear: On page 1367, the last boundary condition equation after Equation 2 should read r = ro vice r = 0; and the third term on the right hand side of the first equation preceding Equation 15 1
The kinetic contributions are obtained by using a predicted value of U at the ( j 1)th time interval, denoted by (U,,, + and are calculated by linear extrapolation
+
Weighting completely to the future value of U in the kinetic term was found to require less iterations and introduced negligible bias compared with other choices. This completes the equation set required to solve simultaneously for the ( U n , j +1)1 vector. The values of (U,,,+ 1)1 are used as the first trial vector in the Newton-Raphson iteration method. The set of simultaneous equations can be represented in matrix form by +
+
s (A481 where is the square matrix of coefficients of the Un,jk,l terms appearingin Equations A18 through A21, the vector S is defined+by Equations A22 through A25, and the unknown vector U contains the values of Un,,+ 1 which are obtained @U =
746
ANALYTICAL CHEMISTRY
should read __ On page 1368, the right hand side of 2T6R2' Equation 17 should have a AT included as a product in the numerator ; U2 should be added to the right hand side of Equation 21 ; the first equation preceding Equation 22 should read
the first term on the right hand side of the first equation preceding Equation 24 should be positive. The first term on the 2 right hand side of Equation 24 should read - - (-2C 3 Dx)+Av--l. On page 1369, the sign of in the S1expression in the Equation 25 set should be negative. On page 1370, the k ninth line should read kl = k2 = -. On page 1371, Equa2 tions A2, A3, and A4 should all have T as the upper limit of integration; the second and third sentences in the first paragraph following Equation A4 should read, "In Equation 17, is first assumed to be equal to U,. A solution is obtained, and the value of is substituted back into the K term"; the U , term in the third sentence of the following paragraph should be U n , On page 1372, the superscript for D in the the secfirst equation is incomplete and should read D1'2; ond equation on this page should read ZCa vice
+
n2
n,,
u,,
