Studies on the pitting corrosion of zinc in aqueous solutions II. Measurement of pitting corrosion currents operating under natural conditions

A simple experimental arrangement was applied for the measurement and the evaluation of pitting corrosion currents operating under natural conditions. The feasibility of the procedure was examined by using Zn as a test metal, K₂CrO₄, Na₂HPO₄ and Na₂WO₄ as inhibitors, and Cl^?, Br^? and I^? as pitting corrosion agents. Both the type and concentration of the inhibiting and corroding agents were varied in a programmed manner. In CrO₄^2? and HPO₄^2? solutions, the pitting corrosion currents started to flow after an induction period, which decreased with increase in the concentration of the attacking agent. In WO₄^2? solutions, on the other hand, initially high currents were recorded due to the reduction of the agent to soluble, non-inhibiting species.In all solutions tested the corrosion current reached steady-state values which depended on the type and concentration of both the inhibiting and the aggressive anions. When keeping the inhibitor concentration constant, the corrosion current varied with the concentration of the aggressor according to: log i_corr = a₁ + b₁ log c_agg On the other hand, in solutions of constant aggressor concentration, with varying inhibitor amounts, the relation was: log i_corr = a₂ ? b₂ log c_inh where a₁(a₂) and b₁(b₂) are constants.The two equations were derived theoretically on the basis of competitive adsorption of the two counteracting agents on the surface of the metal. Comparison between the experimental values of a and b, with the corresponding terms of the theoretical equations was made.The aggressivity of the three tested anions decreases in the order Cl^? > Br^? > I^?, whilst inhibition varied as CrO₄^2? > HPO₄^2? > WO₄^2?.     

Trap mutation in He-doped ion-implanted tungsten

In this work, we report on an investigation of the defect complexes InVe₂He _n in tungsten by means of PAC. The release steps InVe₂He _n InV₂He _n-1 + He were identified forn=1t–5. The dissociation energies, in the range of 2.9–4.5 eV, agree perfectly with the values that have been previously determined by means of THDS. The quadrupole frequency is about 122 Mrad/s forn=1,2 and about 101 Mrad/s forn=3,4. These values are smaller than the frequency of the undecorated vacancy (n=0). The vacancy mutates into a divacancy if it is filled with about 10 He atoms, giving rise to a quadrupole frequency of about 218 Mrad/s. This so-called trap mutation ultimately leads to bubble information. We observed at least three different bubble-associated quadrupole interactions.     

Eriochrome blue S.E. as indicator in chelatometric titrations

Summary The use of eriochrome blue S. E. as a metal indicator for the EDTA titrations of zinc, cadmium, magnesium, lead, nickel and manganese is described. Spot tests for the determination of the sensitivity limits of dectection of the end points are given.     

Metomega chrome cyanine bll as a metal indicator in edta titrations

A study was made of the suitability of Metomega Chrome Cyanine BLL as a metal indicator for the EDTA titration of zinc, cadmium, manganese and lead. Spot tests for the determination of the sensitivity limits are described.     

Synthesis and biological activity of some new aminoacylcarbazole derivatives. Part I

The syntheses of different 9-(N-phthalyl- or N-tosyl- or free aminoacyl)carbazoles and the corresponding derivatives of 3,6-dinitrocarbazoles and some derivatives of 3,6-diamino-9-(N-phthalylaminoacyl)carbazoles (II-XXXII) are described. Compounds VIII, XIII-XVII and XXIII-XXVII were found to be active against a number of microorganisms.     

The thermodynamic behaviour of Sm3+-doped LiKSO4 crystals

The influence of the point defects introduced by means of Sm³⁺ on the thermal properties of LiKSO₄ crystals was studied in the vicinity of the high-temperature phase at 708 and 940 K. The temperature dependence of the specific heat was found to vary monotonously with the Sm³⁺content, while the first transition temperature was unchanged. The change in the value of the specific heat was attributed to the correlation between the defect-defect interaction and the presence of internal local strain generated inside the crystal. The variation of the excess specific heat with the reduced temperature obeys the 3d Ising model.     

Omega Chrome Black PPV, a new metal indicator

Summary The use of Omega Chrome Black PPV for the EDTA titration of zinc, manganese, nickel, cadmium, magnesium and lead is described. The sensitivity limits of detection of the equivalence points are determined. The indicator has been found to be suitable in titrations of mixtures of manganese and zinc.     

Redox polymerization of methyl acrylate in absence and in presence of some inorganic silicon compounds

The polymerization of methyl acrylate in water using ammonium, potassium, and sodium persulphates with sodium bisulphite as redox initiation system was studied. It has been found that ammonium persulphate had the least activity on the rate of polymerization and resulted in the formation of the highest viscosity average molecular weights for the obtained polymers. The rate of polymerization was found to increase with sodium bisulphite concentration in the redox system, but the viscosity average molecular weights were found to decrease with the increase of sodium bisulphite concentration. Addition of some inorganic silicon compounds (containing the same weight equivalent of SiO₂) resulted in increasing the rate of polymerization and decreasing the induction period. The average molecular weights obtained in presence of china clay were found to be the highest and those obtained in presence of talc were the least.