Ammonium aurin tricarboxylate as a reagent in inorganic analysis

Summary Ammonium aurin tricarboxylate produces characteristic colour with various metallic ions. The colour reactions are quite sensitive especially in the case of uranium and thorium besides aluminium and beryllium. The use of the reagent in analysis is suggested.     

On counting triangulations in d dimensions

Given a set of n labeled points on S^d, how many combinatorially different geometric triangulations for this point set are there? We show that the logarithm of this number is at most some positive constant times n^d/2+1. Evidence is provided that for even dimensions d the bound can be improved to some constant times n^d/2.     

Protonated,hydroxo, and mixed protonated - hydroxo species in metal - ligand equilibria: Complexes of thorium(IV) with xylenol orange in aqueous solution solution

Summary The equilibrium constants of chelate formation of thorium(IV) with 3,3-bis[N,N-di(carboxymethyl)-amino-methyll-o-cresolsulphonphthalein (xylenol orange, dcac) at 25° in aqueous solution have been evaluated. The values have been obtained both while considering and ignoring the presence of metal hydroxo species, using the method described earlier. The change in equilibrium constant values obtained in both these situations has been explained by introducing some possible equations, and it has been concluded that the consideration of metal hydroxo species, does not lead to any marked changes in the valules of the formation constants of complex formed, even at higherpH.Presented at the National Symposium on Coordination Chemistry, I.A.C.S., Calcutta, January 1977.     

Ag nanoparticle mediated growth of CdS nanobelts

Catalytic growth of CdS have been carried out on large scale by evaporation of bulk CdS on Ag deposited Si (1 1 1) at atmospheric pressure. The as prepared CdS had wurtzite structure as evidenced by X-ray diffraction. The nanostructures were beltlike with several tens of micrometers length, several micrometers width and few nanometers to tens of nanometers thick as seen by scanning electron microscope and confirmed by TEM studies. The nanobelts were single crystalline in nature and showed reflection corresponding to (1 1 2) and (0 0 2) planes in SAED. The PL studies revealed the green band due to band gap emission and red band due to emission from the surface states. The higher intensity of the defect emission indicated the presence of considerable concentration of surface defects in the as prepared sample. The deposition of CdS could be explained on the basis of catalyst assisted vapor-liquid-solid and vapor-solid mechanism.     

Thermoelectric power of potassium doped lanthanum manganites at low temperatures

The temperature-dependent resistivity and thermoelectric power of monovalent (K) doped La_1−xK_xMnO₃ polycrystalline pellets (x=0.05, 0.10 and 0.15) between 50 and 300 K are reported. K substitution enhances the conductivity of this system. Curie temperature (T_C) also increases from 260 to 309 K with increasing K content. In the paramagnetic region (T>T_C), the electrical resistivity is well represented by adiabatic polaron hopping, while in the ferromagnetic region (T<T_C), the resistivity data show a nearly perfect fit for all the samples to an expression containing, the residual resistivity, spin-wave and two-magnon scattering and the term associated with small-polaron metallic conduction, which involves a relaxation time due to a soft optical phonon mode. Small polaron hopping mechanism is found to fit well to the thermoelectric power (S) data for T>T_C whereas at low temperatures (T<T_C) in ferromagnetic region (S_FM), S_FM is well explained with the spin-wave fluctuation and electron–magnon scattering. Both, resistivity and thermopower data over the entire temperature range (50–300 K) are also examined in light of a two-phase model based on an effective medium approximation.