Determination of carbonate in the presence of hydroxide : Part I. Analysis of first-derivative potentiometric curves

Mathematical consideration of the course of neutralization of a solution containing a moles of a strong base (e.g. sodium hydroxide) and a moles of a salt of a weak dibasic acid (e.g. sodium carbonate) with a strong acid (e.g. hydrochloric acid) shows that the first derivative of the titration curve should contain three maxima. The first, corresponding to neutralization of most of the hydroxide, is small (with height proportional to a^{$\text{1}\text{2}$}), displaced slightly from the equivalence point, and disappears for a less than 0.01 mol l^-1. The second corresponds to the conversion of most of the CO₃^2- to HCO₃^- and its height is almost independent of a. The third corresponds to the conversion of HCO₃^- to H₂CO₃, with height proportional to a^{$\text{1}\text{2}$}. The two minima are independent of a and of the dissociation constants of the weak acid. These conclusions were examined experimentally and were extended to the titration of hydroxide contaminated with a small amount of carbonate.     

Determination of the Wiener molecular branching index for the general tree

The many applications of the distance matrix, D(G), and the Wiener branching index, W(G), in chemistry are briefly outlined. W(G) is defined as one half the sum of all the entries in D(G). A recursion formula is developed enabling W(G) to be evaluated for any molecule whose graph G exists in the form of a tree. This formula, which represents the first general recursion formula for trees of any kind, is valid irrespective of the valence of the vertices of G or of the degree of branching in G. Several closed expressions giving W(G) for special classes of tree molecules are derived from the general formula. One illustrative worked example is also presented. Finally, it is shown how the presence of an arbitrary number of heteroatoms in tree-like molecules can readily be accommodated within our general formula by appropriately weighting the vertices and edges of G.     

Experimental measurement and prediction of hydrate forming conditions in the nitrogen-propane-water system

Experimental data on initial hydrate formation conditions have been obtained for the nitrogen-propane-water system in the L₁HG, L₁L₂H, and L₁L₂HG regions, where L₁ is the water rich liquid phase, L₂ is the hydrocarbon rich liquid phase, H is the hydrate and the G is the vapor phase. The measurements covered a range of temperatures from about 275 to 293 K and pressures from about 0.3 to 17.0 MPa. The concentrations covered for the L₁HG region extended from 0.94 to 75.0 mole percent propane in the gas phase, and for the L₁L₂H region they extended from 83.1 to 99.0 mole percent in the condensed liquid phase. Four-phase measurements were made at concentrations of propane from 18.1 to 71.1 mole percent in the gas phase.The experimental data were used to find a fitted binary interaction parameter for predicting hydrate formation in systems containing nitrogen and propane.     

The autoxidation of 2-(2-aminophenyl)-3- methylindole

Fischer indolisation of 2-aminophenyl ethyl ketone phenylhydrazone using glacial acetic acid saturated with hydrogen chloride as catalyst affords 3-methylindolo(l′:2′-3:4)2-methylquinazoline and 2-(2-aminophenyl)-3-methylindole. The latter compound is autoxidised to 2-(2-amino-phenyl)-3-hydroxy-3-methyl-3H-indole, a reaction which is shown to be dependent upon the presence of the primary amino group at the 2-position of the 2-phenyl substituent and which is much slower than the corresponding autoxidation of 2-(2-hydroxyphenyl)-3-methylindole to 3-hydroxy-2-(2-hydroxyphenyl)-3-methyl-3H-indole previously reported.Nitration of isopropyl phenyl ketone occurs preferentially at the ortho- rather than the meta- positions of the benzene nucleus.     

Thermogravimetric determination of magnesium,potassium and lead by precipitation with dilituric acid

The thermolysis curves of magnesium, potassium, and lead diliturate have established that either the hydrated or anhydrous forms of these precipitates are stable enough for their gravimetric use to be possible. Magnesium and lead were determined by precipitation with dilituric acid while potassium was precipitated with trimethylamine diliturate.     

Adsorption configuration and local ordering of silicotungstate anions on Ag(100) electrode surfaces

X-ray reflectivity, cyclic voltammetry, and scanning tunneling microscopy (STM) are used to examine the structure of alpha-SiW12O4(4-) or silicotungstic acid (STA) adsorbed on Ag(100) in acid solution. The voltammetry shows that STA passivates the Ag surface relative to electron transfer to a solution redox species. STM images reveal the formation of a series of lattice structures, one of which can be associated with a commensurate ( radical13x radical13)R33.69 degrees structural model. X-ray reflectivity measurements show uniquely that STA orients with its four-fold axis perpendicular to the Ag(100) surface and that the center of the STA molecule is 4.90 A above the top layer of the Ag substrate. Analysis of bond lengths leads to a footprint of STA on Ag(100), in which the four terminal O atoms are located near the hollow sites and have a Ag-O bond length of 2.06 A. This bond length is consistent with a strong covalent interaction between STA and the Ag surface.     

Nitrosyl derivatives of tricobaltcarbon clusters

The nitrosyl clusters PPN[YCCo₃(CO)₇(NO)] (Y = Me, Ph, COOH, (C₅H₅)Fe(C₅H₄)) have been prepared in high yield from the reaction of YCCo₃(CO)₉ with PPN(NO₂) in THF, acetone or acetonitrile. Spectroscopic evidence indicates the structure of the nitrosyl anions is derived from that of YCCo₃(CO)₉ by the replacement of two CO ligands on one cobalt atom by a linear, terminal nitrosyl group. The nitrosyl metallates are extremely sensitive to oxidation and attempts to protonate the anions resulted in the reformation of the parent YCCo₃(CO)₉, molecules. The oxidative electrochemistry of the ferrocene complex, PPN[(C₅H₅)Fe(C₅H₄CCo₃(CO)₇(NO)] is also discussed.     

ortho-metallation reactions involving some triphenyl phosphite complexes of osmium

Osmium triphenylphosphine complexes, OsH₄(PPh₃)₃, OsH₂ (CO)(PPh₃)₃ and OsHCl(CO)(PPh₃)₃ react with triphenyl phosphite in boiling organic solvents to yield triphenyl phosphite derivatives which subsequently undergo ortho-metallation reactions.     

Rapid computer simulation of ESR spectra. Conventional ESR of axially symmetric 14N-nitroxide spin labels

A computer algorithm is presented for the simulation of the effect of molecular tumbling on ESR spectra, and is applied to simulation of the conventional ESR signal (the absorption signal detected at the first harmonic of the modulation frequency and in-phase with the modulation frequency, in the limit of low microwave and modulation power) of axially symmetric ¹⁴N-nitroxide spin labels. The algorithm is extremely fast and is economical in terms of computer memory requirements.