Complexation of aluminium, yttrium, lanthanum and lanthanides with 4-(2-pyridylazo)resorcinol (par)

The sensitive reactions between 4-(2-pyridylazo)resorcinol (PAR) and yttrium, lanthanum and the lanthanides can be used for the spectrophotometric determination of these elements. The method has no advantage over other methods for the determination of aluminium and lanthanum. Only M(PAR)H and M(PAR) complexes are formed in solutions where the molarity of the metal ion is greater than or nearly equal to the molarity of the ligand at pH < 7-5. If there is molar excess of PAR, 1:2 complexes may be formed but this is certain only for the yttrium-PAR system. Errors in analysis may result from the simultaneous occurrence of optically different complexes; close control of pH and reagent concentration is essential. Optical and equilibrium data are given for the systems investigated.     

The 1,2,4-triazolyl cation: thermolytic and photolytic studies

The generation of the 1,2,4-triazolyl cation (1) has been attempted by the thermolysis and photolysis of 1-(1,2,4-triazol-4-yl)-2,4,6-trimethylpyridinium tetrafluoroborate (2) and the thermolysis of 1- and 4-diazonium-1,2,4-triazoles, using mainly mesitylene as the trapping agent. Thermolysis of 2 gave mostly 1,2,4-triazole, together with 3-(1,2,4-triazol-4-yl)-2,4,6-trimethylpyridine, 4-(1,2,4-triazol-4-ylmethyl)-2,6-dimethylpyridine, and 4-(2,4,6-trimethylbenzyl)-2,6-dimethylpyridine. Thermolysis of each of the diazonium salts in the presence of mesitylene again gave mainly triazole together with very low yields of 1-(1,2,4-triazol-1-yl)-2,4,6-trimethylbenzene and the corresponding -4-yl isomer in about the same ratio. On the other hand, photolysis of 2 in mesitylene gave mainly 1-(1,2,4-triazol-1-yl)-2,4,6-trimethylbenzene. A photoinduced electron transfer from mesitylene to 2 has been observed and preliminary laser flash photolyses of 2 and the corresponding 2,4,6-triphenylpyridinium salt have been carried out. The observed transients are explained as arising from the first excited states of the pyridinium salts rather than from 1. Ab initio MO calculations are reported and indicate that the predicted electronic ground-state of the triazolyl cation is a triplet state of B1 symmetry with five pi electrons, which corresponds to a diradical cation (1c). Possible mechanisms for the formation of the various products are proposed.     

Einfache Natriumbestimmung durch Ionenaustauscher Lewatit S 100

Zusammenfassung Es wird eine Methode zur Bestimmung von Natrium mittels Tetraphenyloborat angegeben. Mit Hilfe eines stark sauren Kationaustauschers in der Kaliumform wird das Natrium quantitativ und stöchoimetrisch gegen Kalium ausgetauscht und dieses mit Kalignost bestimmt.Durch Verwendung einer neuartigen Säule wird das Volumen des Filtrats gering gehalten.Eine Natriumgesamtbestimmung erfordert etwa eine Stunde Zeitdauer. Die reine Arbeitszeit beträgt 25 min.Herrn Prof. Dr. A. Kurtenacker zum 70. Geburtstag gewidmet.     

Linear crystallization and induction-period studies of the growth of calcium sulphate dihydrate crystals

The linear crystallization of well-formed crystallites of calcium sulphate dihydrate from supersaturated solutions has been studied by a microscopic method at temperatures ranging from 25 degrees to 55 degrees . The activation energy is 16 +/- 1.5 kcal/mole for the fast-growing faces. Induction periods in the crystallization of calcium sulphate dihydrate have been determined as a function of solution concentration at temperatures of 25 degrees and 90 degrees .     

Influence of foreign materials upon the thermal decomposition of dolomite,calcite and magnesite part I. Influence of sodium chloride

The influence of sodium chloride on the course of thermal decomposition of calcite, magnesite and dolomite was studied partly under dynamic, and partly under quasi-isothermal heating conditions. Four different types of sample holders were applied in the experiment, i.e., the partial pressure of carbon dioxide was also different in the four cases. It was found that the presence of sodium chloride reduced the decomposition temperature in every case. The extent of this reduction amounted to about 10°C in the case of calcite, 40–80°C in the case of magnesite, and 10–40°C and 10–20°C for the first and second decomposition stages, respectively, of dolomite.     

A comprehensive survey of the INAA of reference materials

The nature of summary reports now being prepared for issuance, summarizing the results of detailed INAA Advance Prediction Computer Program (APCP) calculations for many widely used reference materials, is discussed and illustrated. For each material, the best photopeak % _rel value (where it is10%) is shown for each of the 12 condition sets (t_i/t_d/t_c) calculated from the input elemental composition. These summary reports will be very useful to groups that use various reference materials as multi-element standards.