1552
ANALYTICAL CHEMISTRY, VOL. 52, NO. 9, AUGUST 1980
basic atomic absorption spectrometer. LITERATURE C I T E D
(2) "Standard Methods of Chemical Analysis", Volume One-"The Elements", Sixth Edition, N. H. Furrnan, Ed.. Robert E. Krieger Publishing Company, Huntington, N.Y., 1975, p 399.
(1) "Analytical Methods for Atomic Absorption Spectrophotometry", Standard Conditions for Copper, September 1976, Perkin-Elmer Corporation. Maine Avenue, Norwaik, Conn. 06856.
RECEIVED for review April 10, 1980. Accepted May 27, 1980.
CORRECTIONS Microcomputer Compatible Method of Resolving R a t e Constants i n Mixed F i r s t - a n d Second-Order Kinetic Rate Laws In this article by Paul B. Kelter and James D. Carr, Anal. Chem., 51, 1828 (1979), a new algorithm for treating mixed first- and second-order kinetic data was reported. The advantages of the algorithm are its speed, simplicity, accuracy, and ability to reject data not adhering to the kinetic model being considered. In this paper i t was stated that Equation 14 is transcendental and therefore must be solved by a successive approximation. This statement is not correct. Equation 14 is readily solved to give Q32 = wp + 1 (1) The quantity of interest, w , therefore equals (Q - l ) * / P . As a consequence of this, first-order and second-order rate constants, as well as absorbance at time t = 0, can be determined with no minimizations, Le., the calculation is a one-pass process. The essential steps in the new program and those that are replaced in the old program are listed below. Old
1@4W "'MINIMI~HTI~W IN FR71;FESS 1E&M LET 1W LET i07liea LET 1886% LET 1@%% LET 1 1 W LET
"
IZ=8 Id=l1 U=W'2*P ( '~-iOI*W*P+B2-1
ld4=2*P*bi^~2*P-i'-P*l~~*~-F-1' Idi=bn/W4 W2=W-WI 111&3 IF W=@ THEN 11688 11288 LET I2=1?+1 113H IF I2XW THEN 11688 114H LET tJ=bl2 11588 iGOTO 187M 116416 "I:HM="bl 1 1 3 3 '"#INIMI:ED IN" 12 '' 1TEEflTII:NS" I
New
163% LET k.fQ?-l!^(UF" 116m "mw',u The authors wish to stress that the old method does not give incorrect answers, only that it is a more complex computation and requires a computing device of greater power. They have calculated several sets of data and find identical answers by both methods. Modification of a Commercial Micrometer Hanging M e r c u r y Drop Electrode In this paper by J. E. Bonelli, H. E. Taylor, and R. K. Skogerboe, Anal. Chem., 1979, 51, 2412 (December), the machining specification for the preparation of the existing plunger shaft for installation of the new plunger tip is incorrect. Instead of =2-56 machine screw, the specification should be for =0-80 machine screw.
