Resorcinol contact time

Structural studies of two complexes with dimethylformamide (DMF) and dimethylacetamide (DMA) were reported. In the former, three types of solvent molecules are embedded in the crystal lattice first, disordered isolated molecules located just above the cavities formed by the resorcinol units second, clusters of four DMF molecules located between the calixarene layers and third, single DMF molecules located inside the layers close to the alkyl chains. The challenge for solid state NMR is to recognize and locate guest molecules in the lattice. CP/MAS, dipolar dephasing and variable contact-time exper-... 

Resorcinol paste is compact and dilEcult to apply. It is easily softened by putting it in a bain-marie at 45° for around 10 minutes. If that is not possible, small blocks of paste should be applied to the patient s skin. Heat from the skin will slowly melt the paste and make it easier to spread, although the resorcinol may penetrate too deeply where contact time has been longer. 

First application (first day) contact time 10-25 minutes. A few minutes after the first application, the patient feels some heat and then a tolerable burning sensation. This sensation starts where the resorcinol has penetrated most rapidly. The cheeks are usually more permeable than the forehead. The areas where the patient first feels burning are the first to be cleaned of the resorcinol paste at the end of the peel. The sensation of acid burning can sometimes become intense, and a yellow serous fluid may be seen to weep through the partially lysed epidermis. In this case, the patient should be given an analgesic for the first night paracetamol (acetaminophen) plus codeine. 

Second application (second day) contact time 20-30 minutes. The resorcinol is left to work for longer 10 minutes more than the first session, or even 15 minutes more on areas that did not react as well on the first application, mainly on the forehead. 

Third application (third day) contact time 30-35 minutes. The third application must be carried out with extreme caution if the resorcinol membrane that is forming has modified the permeability of the skin, epidermolysis is present and the skin has been badly injured rough handling (or paste that is too compact) could pull away the skin and sharply increase the risk of post-peel complications in the form of erythema and pigmentary changes. 

At the end of contact time, the paste is removed with a tongue depressor and a dry gauze pad. A small amount of paste can be left on the skin at the end of the peel so that a thin layer of resorcinol remains to give full results. It is not strictly necessary to take the paste olf in the same order it was applied. It can be left to work longer in certain places to increase the strength of the peel locally - for example on the more resistant skin on the forehead. 

The adsorption isotherms of catechol and resorcinol onto ACC were determined on the basis of batch analysis. ACC pieces of varying weights were allowed to equilibrate with adsorbate solutions of constant initial concentration at 25°C for 48 h. The initial concentration was 7.5 x 10 M for catechol 7.6 x 10 M for resorcinol. Preliminary tests showed that the concentration of adsorbates solutions remained unchanged after 18-24 contact with ACC depending on the type of adsorbate. So, the allowed contact time of 48 h ensures the equilibration for two adsorbates. The equilibrium concentrations of adsorbate solutions were measured spectrophotometrically. The amount of adsorbate adsorbed per unit mass of ACC at equilibrium, q, was calculated by Eq. 21.1,... 

Proton spin-temperature equilibration between the hard- and soft-segment-rich domains of the polyurethane elastomer on the order of 10-100 ms might be considered fast relative to a macroscopically phase-separated blend [26] or copolymer, but slow relative to a strongly interacting mixture [25]. This is reasonable for a microphase-separated material whose solid state morphology has been the subject of considerable theoretical and experimental research. Under fortuitous circumstances, intimate (near-neighbor) contact between dissimilar molecules in a mixture can be studied via direct measurement of proton spin diffusion in a two-dimensional application of the 1H-CRAM PS experiment (Combined Rotation And Multiple Pulse Spectroscopy). Belfiore et al. [17,25,31] have detected intermolecular dipolar communication in a hydrogen-bonded cocrystallized solid solution of poly(ethylene oxide) and resorcinol on the f00-/xs time scale, whereas Ernst and coworkers [26] report the absence of proton spin diffusion on the 100-ms time scale for an immiscible blend of polystyrene and poly(vinyl methyl ether), cast from chloroform. 

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