Model compounds of hydrophilic polymers

Summary From the products of hydrolysis of dimethyl 2-methoxymethyl-2, 4-dimethylglutarate, the pure stereoisomers of 2-methoxymethyl-2,4-dimethylglutaric acid and their anhydrides have been prepared. Alkaline hydrolysis of the stereoisomeric anhydrides yields the corresponding pure stereoisomeric acids which can be transformed to the corresponding pure threo- and erythrodimethyl esters by means of diazomethane. The configuration of the stereoisomeric anhydrides was determined by analysis of¹H-NMR spectra, the configuration of the other compounds was derived from the anhydride structures based on the preparative procedure controlled by¹H-NMR spectra.     

The effect of liquid flow distribution on the behaviour of a trickle bed reactor

A mathematical model has been formulated of the effect of flow distribution of the liquid phase carrying a dissolved reactant on the progress of an nth order, irreversible, catalytic reaction with heat effects in an adiabatic trickle bed reactor. The model has been stated in terms of the density of irrigation, temperature and concentration of the reactant in the liquid, all treated as spatially distributed variables. Provisions have been made to account for the existence of the flow down the surface of the wall, which has no catalytic effect.Local concentration and temperature have been proven to be coupled by the invariant T + Uγc = γU. The same invariant governs also local concentration and temperature of the wall flow. Mathematically, the model is represented by a coupled set of nonlinear parabolic partial differential equations enabling concentration and temperature fields to be obtained for an arbitrary type of liquid distribution and intensity of the wall flow.Numerical solutions have been obtained by the finite-difference method simulating reactors irrigated by liquid distributors as central discs of different radii, or a central annulus, and strongly exothermic reactions with the reaction order ranging between 0.1 and 2. Numerical results have shown the effect of liquid distribution on the overall reaction conversion to be very complex. Optimum initial distribution varies depending on the reaction order as well as the required degree of conversion. In general, however, the entrance region flow pattern may play a significant role in affecting especially reactions exhibiting kinetics close to zero order (hydrogenations). The effect of the wall flow has been found unambigously adverse to reaching high conversions and of increasing importance for low order reactions.     

On the measurement of crystal size distributions in the micrometer size range

The steady state crystal size distribution in a continuous mixed suspension mixed product removal crystallizer has been measured during the precipitati of calcium oxalate trihydrate from aqueous solution. Two different instruments, both working over the size range 1.4–25 μm, were used, a Coulter Counter and an instrument based on the principle of forward scattering of laser light. The form of size distribution obtained with both instruments was very similar and lends confidence to such measurements at these sizes. The crystal number density for sizes less than about 5 μm was much higher than expected from the number density at larger sizes. This behaviour is similar to that found for systems of higher solubility but raises important questions concerning the reasons for such effects.     

Formation of scawtite from mixtures of CaO,magnesite and quartz under hydrothermal conditions

The phase composition of samples prepared under hydrothermal conditions at 200°C from a suspension of mixtures of CaO, quartz and magnesite has been studied. When 10, 20, 30 and 50 wt % of CaO were substituted by magnesite, the mole ratio CaO/SiO₂ being 0,83 and 1,20 - chiefly tobermorite, gyrolite and calcite or scawtite and tobermorite were formed, and the strength of the tested materials was observed to decrease.     

The effect of the overpotential of deposition on the porosity of metal deposits

The porosity of copper deposits on steel obtained by constant and pulsating overpotential electrolysis has been investigated and determined as a function of the overpotential of deposition. Optimal conditions for copper plating on steel from pyrophosphate baths have been established.