The effect of heat on metal incorporated silica gels

Silica gel prepared under varying conditions indicated that, in addition to the pH and kind of acid, the mode of adding the solutions govern the evolution of surface area of the produced xerogel. Co-precipitation with the oxides of iron, copper, or nickel showed a marked effect in decreasing the surface area of the dry gel. Xerogels incorporated with iron oxide suffered from a sharp sintering that appeared upon heating to 900 °C. Copper oxide-incorporated silicas showed a small decrease in surface area at the same temperature. However, silica incorporated with nickel oxide seems to be resistant to heat treatment at 900 °C, and exhibits only a small change in surface area. Acid treatment of the incorporated silicas resulted in negligible variations in surface area, probably due to the low content of oxides.     

The Role of Cations in Some Inorganic Hydrolysis Reactions

Cations which shift certain equilibria from left to right by forming a compound with one of the reaction products were investigated with respect to their kinetic role in the process. Silver ions have no influence on the rate of the hydrolysis of cyanogen iodide. Similarly, cations which form sparingly soluble carbonates do not influence the rate of hydration of carbon dioxide. On the other hand, the hydrolysis of chlorine is accelerated by Ag⁺ and, to a lesser extent, by Cd²⁺ and Fe(III). It is shown that the effect is not due simply to a bimolecular reaction between chlorine and the cation. In the case of Ag⁺, heterogeneous catalysis may play some role, in analogy with the solvolysis of organic halides. In the case of Cd²⁺, there is spectrophotometric evidence for compounds between Cl₂ and HOCl on the one hand, and the cation on the other. It is suggested that these compounds interconvert more rapidly than do the parent substances. A similar mechanism may be operative in the case of Fe(III), and, possibly, also in the case of Ag⁺.     

The removal of radioactive caesium contaminants from simple aqueous solutions

Cs ions can be removed from aqueous solutions by forming a precipitate of copper ferrocyanide which, having occluded the Cs ions, can in turn be floated by means of an anionic collector. Collection was achieved with either α-sulphopalmitic acid or sodium dodecyl sulphate depending on what interfering ions were initially present in the solution. Recoveries of 98–99% were obtained on batch scale experiments and 97.5–98.5% on continuous scale operation. The investigations of the flotation parameters of pH, gas-rate, concentrations of precipitating reagents and collector, as well as the interference effects of other ions are discussed. Using data obtained in batch scale tests, continuous scale experiments were designed and operated.     

Composition of mixed octadecadienoates via ozonolysis,chromatography and computer solution of linear equations

An approach to the analysis of 55 possible nonconjugated positional isomers of octadecadienoic acid is described and tested with mixtures of individual synthetic methyl esters. In the first example, by ozonolysis a sevencomponent mixture consisting ofcis,cis 5,12-, 6,10-, 6,11-, 6,12-, 7,12-, 8,12-, and 9,12-octadecadienoates was converted to aldehydes, aldehyde-esters and dialdehydes. These fragments were separated on a 50 m×0.2 mm free fatty acid phase (FFAP) vitreous silica capillary column. Equations for an arbitrarily restricted 12×15 matrix of linear simultaneous equations and a computer solution of the matrix provided the composition of the initial methyl octadecadienoate mixture. The power and significance of this method became apparent with the observation that only two of the seven isomers in the known mixture were resolved as single peaks by state-of-the-art capillary gas chromatography, but all seven were identified and estimated with acceptable error by the ozonolysis-capillary gas chromatography-computer procedure. In a generalized approach to the analysis of the 55 possible nonconjugated isomers, a computer program selects the appropriate matrix of linear simultaneous equations based on the aldehyde data supplied by the analyst. Twenty of 21 combinations of seven isomeric esters taken five at a time have been analyzed to assess the efficiency of the method. To illustrate applicability at this stage of development, the method has been used to analyze the diene products of the hydrazine reduction of γ-linolenic acid and the diene products from the biological desaturation of isomeric monoenes. The possibility of distinguishing geometric and positional isomers of 18∶2 has been opened by the observed separation ofcis-andtrans-unsaturated aldehydes and aldehyde-esters. Presented in part at the 16th World Congress of the International Society for Fat Research, October 4–7, 1983, in Budapest, Hungary, and at the American Oil Chemists' Society Meeting, May 15, 1986, in Honolulu, Hawaii.     

Creep and drying shrinkage of calcium silicate pastes IV. Effects of accelerated curing

The dependent deformations and evidence of structural changes were measured on pastes of C₃S containing CaCl₂, and on pastes of C₃S or a C₃S/C₂S blend cured at 65°C. It was concluded that the addition of CaCl₂ enhances the role of the “pore component” in controlling irreversible strains even when well-hydrated pastes are dried. The formation of ore stable CSH at 65°C can explain the reduction in time-dependent deformations observed for these pastes. Even though a change in pore size distribution occurs at 65°C, it is not considered to affect irreversible strains in well-hydrated pastes.     

Some Observations on the Effect of Urea on the Dyeing Behaviour of Wool at Low Temperatures

The effect of adding urea to the dyebath on the rate of absorption of reactive and acid dyes by wool, and of acid dyes by other protein bres, has been studied. Possible modesof action of aqueous solutions of urea on wool are discussed. The observed increase in the ite of dyeing in the presence of urea is due to disaggregation of the dye in solution and reduction in dye-protein hydrophobic interactions. The action of urea in promoting fibre swelling is also likely to be a contributory factor.     

The production of salad oil by fractional crystallization with solvents

A fractional crystallization method for the winterization of cottonseed oil with solvents was developed in our laboratories and pilot plant. Small amounts of solvent (e.g., 10% by weight of acetone) were mixed with the oil. This mixture was rapidly chilled to 0°C. and kept at this temperature for 3–4 hrs.; the liquid portion was separated from the solids. After solvent evaporation a salad oil of good quality was obtained. The yield is equal to or better than that obtained with conventional methods. The method is suitable for a continuous operation since rapid chilling can be used, and only a short over-all time is necessary. Great advantages of the process are the use of low amounts of solvent and of a refrigeration system not requiring temperatures below 0°C.     

Side-chain functionalized liquid crystalline polymers and blends, 10: phase behavior and structure of side-chain liquid crystalline ionomers containing ions of d-metals

Novel side-chain liquid crystalline (LC) ionomers containing d-metals Co(II) and Ni(II) were synthesized and characterized. Both families of the ionomers are characterized by the same influence of charged group content in polymer on their phase behavior. The incorporation of 2-3 mol% of metal ions in the nematic polymer matrix leads to the induction of SmA phase and rise in the clearing point. The peculiarity of their phase behavior in comparison with the earlier investigated LC ionomers with alkaline or alkali-earth metals is the full destruction of the mesophase at the concentration of d-metal higher than 12 mol%. This phenomenon was associated with the well-known ability of the transition metal ions to form various complexes that, in the case of LC ionomers, can negatively influence the ordering of the side mesogenic groups. The proposed structure of the LC ionomers is discussed in comparison with the metallomesogenic polymer systems.     

Wet milling: A model based on hydrodynamics and particulate media mechanics

A mechanism for force transfer from the active tool surfaces of a mill to the particles in wet grinding is advanced. Use is made of the observation that in some mills a well defined gap develops between the active tool surfaces. Experimentally it can be demonstrated that a squeezing action on any slurry after an initial phase of slurry expulsion at constant concentration ($\text{oozing}$) results in an increase in the concentration in the squeezed zone, when only liquid is expelled ($\text{consolidation}$). The transition between these stages is discontinuous and can be understood from hydrodynamics and particle interaction. This phenomenon is shown to explain the formation of a distinct load carrying particle bed, apparent as the gap in wet milling.The resulting bed permits force transfer of the same nature as in a stressed particulate medium. Stresses in particulate media are transferred through stress chains forming a stress fabric. Stress concentration is a typical feature of such systems and is a function of the bulk. At sufficient load on the system one particle in this stress fabric will reach its limit of strength. The stress fabric simultaneously breaks down. The resulting denser system will on further compression develop another stress fabric with less stress concentration. Thus a higher load is required for the next particle failure. Eventually particle failure will stop. Mixing and shuffling the charge will result in new particle configurations with a high probability of higher bulk and higher stress concentration. In this new configuration particle failure will again be possible at low applied load to the system.The model explains the mechanims of bed formation in mills, the necessity of particle mixing for progressive particle failure and also identifies a neglected energy consumption factor in wet milling. An adaption of the model to dry milling is indicated.