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recovered from the carbon in that work may have resulted from reactions similar to those reported here.Reactions of chlorine and organic compounds on activated carbon have several environmental implications. The quiñones and polyphenols formed on the carbon surface are of interest since they are toxic to aquatic plants (19) and participate in redox reactions in the environment. Quinones have also been shown to be toxic to blue-green algae (20) and to inhibit the photosynthesis of green algae (21).The columns in these experiments were run for only a short period of time, and many oxidized compounds were found in the inlet to the bed. It would be expected that these compounds could be displaced further into the column during the life of the bed and eventually pass into the effluent. Although outside the scope of the present study, it would be interesting to observe the conditions under which displacement could occur and the concentrations and biological properties of the effluent organic compounds.

~~The ion-exchange isotherm for Ca2+ exchange with sodium zeolite A was determined at 25 OC by using a novel solid uptake analytical scheme and a Langmuir adsorption model, resulting in an improved value for the thermodynamic equilibrium constant. Ion-exchange isotherms and approximate thermodynamic equilibrium constants were also determined for calcium zeolite A exchange with Pb2+, Cd2+, and Cu2+. Pb2+ and Cd2+ exchanges were found to be reversible, whereas Cu2+ exchange was not, probably due to Cu(OH),(s) precipitation upon or within the zeolite.Ion exchange was attempted but found to be irreversible with C$+, Hg2+, Fe3+, and A13+. Except for Cr3+, these ions caused zeolite A structure degradation, probably through extensive proton exchange. Cr3+ exchanged partially and then formed a precipitate. Data obtained in this work provide an improved understanding of the possible environmental water effects of zeolite A.

Silver oxide is stable in boiling water and decomposes but very little at room temperature in strongly alkaline solutions. The presence of Ag~O does not affect this stability, but the presence of unoxidized silver does increase the rate of decomposition. When AgO dissolves in strongly alkaline solutions the dissolved form is primarily AgO and Ag(OH)~-. The standard free energy of formation of the latter is --85,380 cal/mole.

Precipitation boundaries in alkaline calcium-pyrophosphate and calcium-ethane-1-hydroxy-1,l-diphosphonate (RHDP) systems have been determined and an interpretation is given in terms of mass action principles ignoring activity coefficients It is found experimentally that In systems containing ligand in excess of the stoichiometric amount the ratio of total metal to total ligand is generally less than unity for pyrophosphate, whereas the ratio for EHDP approaches the value of 2 The pyrophosphate boundary is shown to be that of a typical nonpolynucleating ligand, and the EHDP data are interpreted in terms of a "core-links" polynuclear complex model which postulates species of the general form Cazn--1Ln2-= CaL(Ca2L),-i2-From the analyses it is estimated that log Knl(Ca2P~07) = 2 80, pK80(Ca~P207) = 12 87, log KI1(CaEHDP) = 5 60, log Kzl(Ca2EHDP) = 4 18, log Kz,-,,, = 4 83, and pK,,(Ca,EHDP) = 14 60 Low molecular weight phosphates and phosphonates tend to precipitate from solution when allowed to react with alkaline earth ions, particularly calcium. This is in contrast to the behavior of aminopolycarboxylates, e.g., ethylenediamine-N,N,N,'N'-tetraacetic acid (ED-TA), whose alkaline earth salts are soluble in amounts approaching 1.0 M.l The tendency of phosphates and phosphonates to precipitate makes impossible or severely restricts the use of a number of techniques for the determination of soluble complex species. The present work was undertaken for the purpose of determining the extent of these restrictions in calcium-pyrophosphate (PP) and calcium-ethane-1 -hydroxy-1 ~ 1-diphosphonate (EHDP) systems. Experimental SectionChemicals.-Stock solutions of CaC12 were prepared by weight from "Baker Analyzed" CaClz * 2H20. Tetramethylammoniuni hydroxide (TMAOH) solutions were prepared from commercial aqueous solutions (either Eastman Chemicals 10% solution or Matheson Coleman and Bell 25% solution) by passage through a column of Dowex 21K anion exchanger in the hydroxyl form. Tetramethylammonium chloride (TMACI) stock solutions were prepared by weight from Eastman Chemicals TMAC1. The source of E H D P was the acid monohydrate prepared by the Brooks method2 and recrystallized twice from water. This was subsequently neutralized with TMAOH in the Preparation of stock solutions. "Baker Analyzed" Xa4Pz0,. ~OHZO was.converted to (TMA)dP207 by ion exchange using Domex 50W-X2 in the TMA+ form (prepared by repeated aiternate washings with TMACl and TMAOH).Procedures.-All stock solutions were passed through 0.45-p Millipore filter paper and then kept in a nitrogen atmosphere throughout the sample preparations.Each point in the right branch of the P P precipitation boundary (points for which CL > 2Ca1) and points in the vicinity of the minimum were determined by CaCl2 additions to series of aliquots of each of several stock P P solutions up to the point of precipitation. In these cases precipitation was usually very rapid and voluminous so that end points could be determined visually. The actual point of precipitation was taken to be ...