Suspension of Manganese Dioxide in Detergents.

Abstract

The controlled formation of stable dispersions of solid powders in liquids is of both theoretical and practical interest. The suspendibility of a powder depends upon and aids in the understanding of the surface properties of the disperse phase, as these affect, cohesion between particles in various media and as they result, in selective adsorption of ions or molecules from solution. Moreox-er many commercial products, such as paints and printing inks, consist of finely clix idecl solids dispersed in liquids. It also seems likely that the relative effectiveness of detergents may be closely related to their ability to stabilize suspensions of removed dirt.In the present work the effectixre particle-size distribution of powdered manganese dioxide was determined in a number of media to aid in ascertaining the mechanism whereby relat.ix'ely stable dispersions may be produced in aqueous solutions. The amounts remaining in suspension after a 4-hr. settling period xvere also determined as a function of concentration in aqueous solutions of Aerosol OT, Oronite, Hyamine 1622, Triton X-100, sodium oleate, and p-t.oluenesulfonic acid. Characteristically, the curxres of amount suspended vs. concentration of dispersing agent pass through a maximum at low concentrations. It seems likely that the shapes of these cuives, as well as the differences between different, detergents, are explicable in terms of varying effectix'eness in disgregation of the aggregates xvhich normally form on introducing a powder of given ultimate particle size into a pure liquid. The mechanism by xvhich this is accomplished appears to be through change in the zeta potential effected by adsorption of ions from solution. MATERIALS Baker's c.p. manganese dioxide powder was used throughout this work without further purification.Aerosol OT was obtained from the American Cyanamid Company in the form of "100%" pellets and used directly. It is the sodium salt of dioctylsulfosuccinic acid.Oronite Actix'e, made by the California Research Company, was a sample receix'ed through the courtesy of the Lever Brothers Company, and described as 1 ITesentcd at the Twenty-second National Colloid Symposium, which was held under the auspices of the Division of Colloid Chemistry of the American Chemical Society at Cambridge. Massachusetts, .June 23-2.5, 1948.

Rates of OH Radical Reactions. I. Reactions with H2, CH4, C2H6, and C3H8 at 295 K

“…The value for C2H6 agrees well with both the recommended value and the value of Greiner (16). The reported values for C3H, (16,21,22) differ by over a factor of 2.…”

“…The value for C2H6 agrees well with both the recommended value and the value of Greiner (16). The reported values for C3H, (16,21,22) differ by over a factor of 2. Our value agrees well with the higher value of Gorse and Volman (22), determined indirectly, relative to the rate constant of the reaction OH + CO. For personal use only.…”

“…Prominent among the direct studies is the pioneering work of Greiner (ref. 16 and references therein) who used the flash photolysis kinetic spectroscopy technique. The rate constant of the Hz reaction, in particular, is more reliably known and is used to test our technique.…”

Evaluated kinetic and photochemical data for atmospheric chemistry: Volume II – gas phase reactions of organic species

“…The rate coefficients from these studies Baker et al, 1970;Baldwin and Walker, 1979;Hucknall et al, 1975; are fitted to the three parameter expression, k=CT 2 exp(-D/T ), resulting in k=1.81×10 −17 T 2 exp(114/T ) cm 3 molecule −1 s −1 over the temperature range 230-760 K. The preferred Arrhenius expression, k=A exp(-B/T ), is centered at 260 K and is derived from the three parameter expression with A = Ce 2 T 2 and B = D + 2T . The preferred values are in good agreement with the room temperature absolute and relative rate coefficients of Greiner (1970), Stuhl (1973, , Paraskevopoulos and Nip (1980), , , , , Barnes et al (1986), Behnke et al (1988) and Chuong and Stevens (2002), which were not used in the evaluation of the rate coefficient.…”

“…Preferred values are based on an average of the data from , Kuo and Lee (1991), Fulle et al (1997), Chuong and Stevens (2000), Klein et al (1984), Atkinson (1994, Davis et al (1975), Howard (1976, Greiner (1970), Morris et al (1971), Overend and Paraskevopoulos (1977), Atkinson et al (1977), , Cox (1975) and Vakhtin et al (2003), where the latter work showed the lowest scatter and, therefore, is given the highest weight. Falloff curves are constructed with the calculated F c =0.48 from Fulle et al (1997).…”