The dissociatio2 constants of m-, and Pphenylenediaminetetraacetic acid (m-, and $-, PDTA) have been determined potentiometrlcally at room temperature (about 25'C) in an ionic strength oi 0.10 M K N 0 3 . The stability cmstatns of their metal complexes have also been determined by UV spectroscopic, potentiometric, and polarographic methods. The formula of the metal complexes by spectroscopic and polarographic methods are both in good agreement to k e 1 : l .Cu>Ni>Zn>CO>Cd>Mg,Which is in accordance with Irving-William stability order.The order of the stability of the metal compIexes is:
I. In t'roductionAlthough nz-, and 9-PDTA had long been used as chromatographic exchange r e~i n s c~'~) t o separate like-charge ions by their weak complexing p3wer; very little information of their chelating behavior has h e n reported. In this study, their formula and stability with Cu, Ni, Zn, Co, Cd, and Mg, Ca, Ba, Sr, were determined. The calculations were treated with a systematic algebratic rn~thodC;'~) a n d carried out by IBM 1620 with a computer programmi n g F
Calculations(1) Potentiometric method. (A) Determination of dissociation constants. From the equilibrium equations of four stepwise dissociations, mass balance and electroneutrality relationships, we can derive the equations: --*Present address: Chung Shan Institute of Science and Technology. MY Cu-($-PDTA) Ni-(p-PDTA) Co-(#-PDTA> Zn-(#-PDTA) Cd-WPDTA) Mg-(pPDTA) Ca-CpPDTA) S r-(PPDTA) Ba-(pPDTA) Cu-(m-PDTA) Ni-(m-PDTA) Zn-( m-PDTA) CO-( m-PDTA) Cd-( m-PDTA) Mg-( m-PDTA) Ca-( m-PDTA) Sr-( m-PDTA) Ba-( m-PDTA) These are the average value Of m'cllti-determinations.
The iron‐diethylenetriaminepentaacetic acid (DTPA) system has been investigated polarographically over the pH range 3–10 in the absence of maximum suppressor. The iron (III) complex is reversibly reduced at the dropping mercury electrode. Polarograms of mixtures of iron (III) and iron (II) yield a composite cathodic / anodic wave in the presence of excess DTPA. The half wave potential of the system is constant in the pH region 5.5–9, and from this the ratio of the stability of iron (III) DTPA to iron (II) DTPA has been evaluated. The stability constant of the ferric complex has been obtained from a spectrophotometric analyse of its dissociation equilibrium in 0.4–1.0 M perchloric acid medium at wavelength 380–520 mμ. μ dependence of the acid dissociation constant of DTPA verified that the Davies quation can be extended to μ = 1.0
Petroleum cokes, made from gas oil fraction of crude oil produced in different oil fields in Taiwan, were analyzed in ppm level for boron, vanadium, titanium, iron, calcium, aluminium, magnesium, chromium, cobalt, manganese, nickel, molybdenum, and copper.
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