Nucleophilic subtitution of bromine by amines on (E)-α-(bromomethylene)glutaric acid ester leads to the corresponding enamines in high yields. Stereochemistry of the corresponding products is determined.
T. Ben Ayed, H. Amri, M.M. El Gaïed J. Villiéras
Pages 219-222
CA membranes are prepared according to Manjikian technic. Two casting techniques are tested : manual and automatic. Membranes are characterized on a laboratory hyperfiltration cell. The variation of performances (represented by Water Permeation Rate and Salt Rejection) with constitution parameters of the casting solution and with characterization conditions are investigated.
E. Ferjani, M. Jedidi, M.S. Roudesli
Pages 223-232
We have studied the dissolution kinetics of stainless steel 17-8 in various H2SO4 solutions with concentration varying from 0 to 100% by weight and having a temperature between 40 and 100°C. We find that the kinetics has a maximum corresponding to a [H2SO4] max which decreases from 55% at 40°C to 43% at 80°C. The first stage of attack corresponds to a preferential liberation of Cr and Ni. This occurs along a thickness of about 40 µm and can be explained by the continual formation of a passivation layer rich in Cr and Ni. This formation involves a migration of these elements from under layers to the surface.
N. Frini, M. El Maaoui
Pages 233-240
Diffusion equation under conditions of diffusivity variation with concentration is solved numerically by Crank-Nicholson method. A simple exponential dependence of diffusion coefficient with concentration is assumed.Comparison of experiments with theory shows that the model describes the adsorption kinetics adequately and allows the knowledge of the diffusional coefficient parameter.
M. Baguenne, A. Bellagi
Pages 241-253
The effect of flow pulsations on the current reduction at a tubular cathode has been studied theoretically in the range of Reynolds number going up to 860, the amplitude and the frequency varying respectively from zero to 4.5 cm and 2 Hz. The most important result of the application of the model, of which the convenience has been tested in steady flow, is that the transfer rate is decreased at low frequencies and amplitudes compared to the value at steady state ; the improvement is more than 300% when the amplitude or the frequency increases.
A. Gadri, A. Ratel, S.S. Romdhane, G. Lacoste
Page 255-267
In this paper, we study the damping effect of clothes during abrupt variation of ambiant temperature and humidity conditions. We showed that this effect is directly related to the cloth-mass and that the influence of fibre quality is practically of little importance.
H. Derbel, A. Ayadi, G. Serin
Pages 269-279