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Following previous researches on the oxidation of phloroglucinol 1 )2 )3 ), we investigated the kinetics of the oxidation of 2.4-dimethylphloroglucinol by K3Fe(CN)6. Our aim was to examine whether this oxidation could be described by the same mechanism as was found with phloroglucinol itself4 ). In addition, we wanted to obtain some data for a more detailed insight into this mechanism, as was done by Weissberger et al. 1 ) 2 ) 3 ) in the case of derivatives of hydroquinone.

Amorphous silica accelerates the hydration rate of 3CaO,SiO2. This acceleration can be explained by assuming that the silica, by lowering calcium- and hydroxyl-ion concentrations during the first minutes of the hydration, increases the conversion rate of a first protective hydrate layer into another less protective one. In Portland cement pastes, not only hydration of alite but also consumption of sulphate are accelerated, as judged by calorimetric experiments.

The results of following the quantities of free Ca(OH)2 in tricalcium silicate (3CaO.SiO2) of portland cement during the hydration and the influence of the presence of free CaO on the reaction are in agreement with the hypothesis of Stein and Stevels with regard to the hydration of 3CaO.SiO2 (CA 61: 9280g). The hydration process was studied by ir spectra and the electron microscope. When 3CaO.SiO2 comes in contact with the water, the hydrate (I) which is not distinguished from the 3CaO.SiO2 by an electron microscope is formed close to the 3CaO.SiO2 surface. Hydrate I has a very high CaO/SiO2 ratio (.apprx.3:1 moles) and strongly retards further hydration. Hydrate I is converted to a 2nd hydrate (II) which retards the hydration reaction less and has a lower CaO/SiO2 ratio. Once nuclei of hydrate II are formed the conversion takes place with a higher velocity and hydrate II converts to hydrate (III), the poorly crystd. hydrate with a CaO/SiO2 mole ratio >1.5 (tobermorite gel). The transition from hydrate I to hydrate II is accelerated by a decrease in the Ca2+ and OH- concn. in the water phase under which the formation of hydrate II nuclei is accelerated. [on SciFinder (R)]

Electrolytes with monomer and polymer organic cations act predominantly like the corresponding sodium salts in the same concentration. Electrolytes with organic anions vary in action from a retardation of ettringite crystallisation only (sodium oleate) to a complete inhibition of all hydration reactions during the first days polymer anions especially have a very strong effect. The results are in accordance with the concept of a positive surface charge on hydrating cement particles as well as on the hydration products.

Experiments by isothermal calorimetry, indicate that the hydration of 3CaO·SiO2 (C3S) is influenced very little by gibbsite; it is influenced by bayerite to a somewhat larger extent. In the presence of amorphous Al(OH)3 the reaction of C3S with water shows a very complicated course and gives four heat peaks. If CaO is added in addition to this Al(OH)3, the third and the fourth heat peaks are more pronounced. From qualitative d.t.a., infra-red, electron-microscope and X-ray investigations, as well as from quantitative X-ray analysis, a reaction mechanism is proposed. The quantity of C3S reacted, determined by means of quantitative X-ray analysis, is greater during the reaction of 2·00 g C3S with 0·40 g amorphous Al(OH)3, 0·08 g CaO and 2·00 ml water, than during the reaction of 2·00 g C3S with 2·00 ml water.

The influence of some non-ionic organic additives, dissolved in the water used for mixing cement pastes, on cement hydration was determined by isothermal calorimetry. The additives, all poly-alcohols, exert a retarding action on cement hydration. Glycerol has, in addition, a particular influence on the crystallisation of ettringite and calcium hydroalumino-monosulphate, accelerating the consumption of sulphate ions.

The existence of free radicals in the oxidation of phloroglucinol could be proved by initiating the polymerization of styrene.

High precision viscosity measurements of electrolyte solns. were used to obtain information about interionic interactions. In solns. of Me4N+ (TMA) silicates values for the A and D coeff. in the Jones-Dole equation are significantly higher than for Na and K silicate solns. Ion assocn. between cations and anions in the silicate solns. studied is excluded by EMF measurements. The A and D coeffs. of solns. which contain both alkali metal and TMA silicate were in the range of the values of alkali metal silicate solns. As an explanation for this behavior probably hydrophilic and hydrophobic structured solvent regions are present around resp. the silicate and the TMA which cannot overlap. This causes a repulsion between these ions superimposed on the electrostatic attraction. [on SciFinder (R)]

Coacervation (liquid/liquid separation) takes place in aqueous solutions containing short chain tetraalkylammonium (TAA) and silicate ions when other ions (Na+, Br) are present. The TAA bromide is predominantly present in the upper layer and the sodium silicate is mainly present in the lower layer. The coacervation can be described using the activity coefficients of the two separate salts and a RedlichKister type excess Gibbs free energy. Since part of the Gibbs free energy is dependent on the enthalpy of hydrophobic hydration of the TAA ions, the driving force for coacervation is ascribed to a mismatch of the hydration layers around the silicate and TAA ions.

The adsorption of tetraalkylammonium (TAA) ions on silica shifts the isoelec. point to higher pH values. The IEP shift increases with increasing alkyl chain length. Also, tetraethylammonium (TEA) and tetrapropylammonium (TPA) ions can be adsorbed in larger amts. than tetramethylammonium (TMA) ions. The chemisorption of TAA ions can be explained by assuming an attraction between hydrophobically hydrated regions around surface siloxane bridges and around the TAA ions. The adsorption data of TMA ions are compatible with the stimulated adsorption model. [on SciFinder (R)]

Problems encountered in applying the marginal regeneration concept introduced by Mysels for describing drainage of free liquid films with mobile surfaces include the understanding of the dependence of the phenomenon on direction. This can be explained by the surface tension gradient in the film: new film elements entering from the border stretch especially in the vertical direction. Therefore the film/border transition at the top of a film drawn in a frame does not show turbulence caused by marginal regeneration. At the bottom it does show marginal regeneration phenomena but these are there not very active in promoting drainage because new film elements stretch in a direction perpendicular to the border/film contact line. At the vertical film/border transitions the new film elements stretch along the contact line and by so doing reinforce outflow from adjacent regions. This makes these border/film contact regions especially active with regard to film drainage.

The pressure in a Plateau border is calculated from the tatter’s profile measured by light interference, with the objective of better understanding the phenomenon of marginal regeneration. The local pressure in the border, at small heights above the bulk liquid, unexpectedly turns out to be lower than the hydrostatic equilibrium pressure. This can be understood through flows in the border caused by a surface tension gradient at the border/film transition. Such flows in the Plateau/border (upwards near the film, downwards far away from the film) have indeed been observed, by flow visualization through addition of solid particles.

A new, theoretically more satisfactory, definition for the relative viscosities of suspensions in non-Newtonian media is presented, according to which viscosities of suspension and pure liquid should be compared at equal liquid phase viscosities. Theoretical implications of this definition have been investigated, especially for very dilute suspensions. Rheological data of suspensions in liquids with a wide range of degree of pseudoplasticity have been analysed. According to the new definition the Einstein viscosity coefficient of these suspensions is 2.5 independent of the amount of pseudoplasticity.

A poly(vinyl chloride) membrane electrode, based on the ion-pair complex of tetramethylammonium bromide (TMAB) with sodium tetraphenylborate, is described. The electrode exhibits a linear response with a slope of 49 mV per decade of concentration at 20 °C within the range 1 × 10–4–0.1 M TMAB, at an ionic strength of 0.1 M NaBr. The effect of the pH of the test solution and the interference of other cations and SiO44–(or silicate ions of lower charge such as HSiO43– or H2SiO42–) were studied. Potentiometric titration was used to determine TMAB, in the presence of SiO44–, with satisfactory results.

The surface charge of Ca3Al2(OH)12 in water and NaOH solutions is negative when the solution is saturated towards this compound. When Ca3A12(OH)12 is formed during the reaction of Ca3A12O6 with water and NaOH solutions a positive surface charge is present. This positive charge is also found for other hydrates existing during this reaction; it indicates a disturbed surface layer with excess Ca2+ ions on the solid. Further it was shown that the absolute value of the surface charge calculated with the change of the activity coefficient in the diffuse double-layer taken into account is smaller than calculated with the equation without this correction.

The reaction of 3CaO,Al2O3 with water in the presence of CaSO4,2H2O is investigated in suspensions and in pastes. In both, essentially the same sequence of reactions is found, the hydration products being (in the order of their appearance) ettringite, hydrous alumina, calcium aluminate hydrate monosulphate, and sulphate-free hexagonal aluminate hydrates. In pastes, indications of water transport as an important factor in determining the reaction rate are found. Acceleration of the reaction after consumption of most of the sulphate ions present is probably due to chemical conversion of a retarding hydrate layer.

Hydration of pastes of 3CaO, Al2O3 with water shows two different heat effects: (1) on the first contact of the 3CaO, Al2O3 particles with water, (2) when crystallisation of the ultimate hydration product, the cubic 3CaO, Al2O3,6H2O, from the intermediate hexagonal calcium hydroaluminates becomes more pronounced. Addition of 3CaO, Al2O3,6H2O shifts the second peak to earlier times and accelerates the hydration. The results appear to be at variance with a mechanism involving particle disintegration through crystallisation of hydration products in surface cracks, as a cause for the second peak. The results suggest that water transport through a layer of hydration product is the rate-determining step, and that the layer is likely to be removed partly by being dissolved when 3CaO, Al2O3,6H2O is formed predominantly.

Dielectric constants and loss tangents of a Portland cement paste were measured during and after hardening in the frequency range 60 c/s-300 kc/s.

Measurements of the diffusion coefficients of products of the oxidation of phloroglucinol indicate that substances are formed containing a number of benzene rings per molecule.

The phase diagram K2WO4-WO3 in the vicinity of the eutectic point is presented and X-ray powder diffraction data of the solid compounds involved are tabulated. In addition to the stable compounds K2WO4, K2O · 2WO3, K2O · 3WO3 and K2O · 4WO3, two metastable compounds of as yet unknown composition may be formed.

Experiments on the hydration of 3CaO.Al2O3 in a solution of Ca(OH)2 in the presence of CaSO4.2H2O are described. An approximate theoretical treatment of the retarded stage of this reaction is offered on the basis of water transport through a calcium hydrosulphatoaluminate (ettringite) layer on the 3CaO.Al2O3 particles as the rate-determining step of the reaction. The water transport may be effected either by diffusion or by Poiseuille flow. The most plausible explanation of the experimental results is that the deposition of ettringite on the surface layer continues during the retarded stage, and that the surface layer expands at its outside more rapidly than the particles themselves shrink in the course of the reaction.

With the oxidation of phloroglucinol, phenomena are observed reminiscent of humification processes. It is suggested, that in discussing humification more attention should be paid to the oxidation of phenols, which are not likely to give quinones when being oxidised.

Glass formation in alkali molybdate systems is investigated through measurements of the critical cooling rate, i.e. the cooling rate necessary to prevent crystallization entirely. Similarities and differences with alkali tungstate systems are noted, and the latter are explained by postulating a more continuous transition of the molybdenum ion from tetrahedral to octahedral coordination with decreasing alkali oxide content of the systems as compared with the behavior of tungstates, where tetrahedral coordination is found in all glasses. In addition, disproportionation of dimolybdate ions into monomers and higher polymeric units is assumed to be less pronounced in molybdate systems than the disproportionation of ditungstate ions in the corresponding tungstate systems. Density and thermal expansion data on molten alkali molybdate systems indicate that glass forming melts have a relatively spacious structure, in accordance with the idea that glass formation is facilitated by the formation of chains of (distorted) tetrahedra.

Information on interfacial mass transport of cadmium in cadmium sulfide suspensions and er equilibrium conditions has been obtained by probing with a radiotracer for cadmium. The transport of Cd2+ ions from the cadmium sulfide solid particles to the saturated solution and visa versa is followed by adding radioactive 109Cd2+ to the solution and measuring the amount of radioactivity present in the solution as a function of time. The amount of exchangeable cadmium in or at the solid/liquid interface, which is deduced from the final value of radioactivity in the solution appeared to be 1.8 to 2.3 times the amount of cadmium in one lattice layer. Compartmental analysis of the experimental data revealed that 4 different cadmium species are involved in the exchange processes, one of which being the cadmium in the bulk of the solution, and another one, representing 40% to 50 of one lattice layer, which exchanges rapidly with the solution in comparison with the other two species left.

The viscosity of suspensions of glass spheres (15 – 80 μm) in aqueous glycerol decreases at a given solid volume fraction φ with increasing particle size. In such suspensions, no rheologically measurable effects of coagulation are found. The influence of particle size can be understood by immobilization of the liquid between surface irregularities.

Removal of excess water from cement/sand/water mixes can be effected by electroosmosis with an efficiency of several hundred g per Watt sec, if an additive is applied which increases the absolute value of the zeta potential.

Amorphous silica influences tricalcium aluminate (C3A) hydration both in pastes and in suspensions. Two heat peaks are found by isothermal calorimetry during the paste hydration of C3A. The addition of amorphous silica causes the second heat peak to shift towards shorter reaction times and become more pronounced. In suspensions, the change in ion concentration in the water phase is not influenced by the presence of amorphous silica except that the change in concentration occurs more quickly. Quantitative X-ray analysis shows that more 3CaO.Al2O3.6H2O is present in suspensions containing amorphous silica than in silica-free suspensions at equal hydration times.

Kinetic experiments indicate that the first step of the oxidation of phloroglucinol by Fe (CN)6− − − is reversible. The equilibrium concerned, however, is not stable, since one of the species participating, i.e. the first oxidation product of phloroglucinol, is broken down irreversibly. Some data are given about the reaction rates concerned, and the existence of a free radical as an experimentally accessible substance is established.