Dosage de petites quantités de chlorate

A rapid titrimetric method is described for small quantities of chlorate by means of a standardised solution of helianthine. It is possible to determine 10 γ of NaClO₃ to about 5 %.     

M/'ethode d'analyse qualitative des cations sans s/'eparations syst/'ematiques

The authors have formerly described a qualitative method for the analysis of Cations according to which separations were reduced to a minimum, each metal being detected by an independent test.They presently seek to improve this method, with special regard to the case when small quantities of an element are to be found in the presence of large proportions of one or more other cations.In this first paper are given the results for the following metals arsenic, tin, antimony, bismuth.     

Utilité de la définition de brönsted des acides et des bases en chimie analytique

Brönsted's definition of acids and bases presents the following advantages: One may reason along the lines of the acid-base couple and the proton exchange just as done in the case of an oxidation-reduction couple and the electron exchange. The force of the acid is connected with that of the corresponding base.The acid or basic character of certain compounds is evidenced by their tendency to exchange protons, something that does not necessitate the use of “hydrolytic” phenomena.Properties of “strong acids” and “strong bases” are explained.The formulas of the pH of acid solutions, basic solutions, or salt solutions are unified and their use simplified.In acidimetry the reasoning is simplified, and complex problems may be approached with more facility.In the case of non-aqeous solvents that offer great possibilities in acidimetry spbrönsted's theory permits predictions about limitations in the acidityscale. It furnishes an explanation of phenomena in inert solvents.     

Synthesis of thermosensitive guar‐based hydrogels with tunable physico‐chemical properties by click chemistry

Thermosensitive guar‐based hydrogels are obtained in water solutions by copper‐catalyzed 1,3‐dipolar cycloaddition between alkyne‐functionalized guars and α,ω‐diazido‐poly[(ethylene glycol)‐co‐(propylene glycol)]. Characterization by TGA, HR‐MAS ¹H NMR, and rheology have shown that hydrogels with tunable physico‐chemical properties, such as crosslinking density, viscoelasticity, swelling ratio, and so forth, could be obtained by varying the guar molar mass, the degree of alkyne functionality, the guar/crosslinker weight ratio, and the reaction temperature. Based on swelling measurements, it has been shown that the thermal sensitiveness of guar‐based hydrogels is fast, reversible, and intimately related to the weight fraction of the thermosensitive crosslinker in the network. Finally, the monitoring of doxorubicin hydrochloride release has demonstrated the potential of these hydrogels as temperature‐dependent drug release devices. The robust, efficient, and orthogonal approach described herein represents a general approach towards the development of well‐controlled guar‐based hydrogels using α,ω‐diazido crosslinkers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2733–2742, 2010     

Restricted rotations and stereodynamics of aziridine-2-methanol derivatives

‘Gear-like’ rotations of simple C-C bonds have been observed in some aziridine methanol derivatives. These restricted rotations have been studied by dynamic and multinuclear magnetic resonance experiments, and the barrier for rotations of Csp³-Csp³ and Csp³-Csp² bonds have been calculated. The role of an intramolecular hydrogen bond on the stereodynamics has also been demonstrated.     

Efficient electron transfer through a triazole link in ruthenium(II) polypyridine type complexes

Spectroscopic, electrochemical and theoretical characterisations of photoactive systems readily assembled via click-chemistry show an efficient bi-directional charge shift through the triazole link.