Buddhadev Sen

Hydrogen generation by hydrolysis of sodium tetrahydroborate: effects of acids and transition metals and their salts

A study was undertaken in order to investigate the potential of NaBH4 as a precursor fuel source for a hydrogen–oxygen (air) fuel cell. At appropriate initial acid concentration, hydrolysis of NaBH4 is nearly 80% complete in 2.5 min, and nearly 90% complete in 10 min at 21.7 °C. Transition metals and their salts also accelerate hydrolysis of NaBH4. The effect of transition metals is characterized by zero-order kinetics.

Spectrophotometric determination of traces of formaldehyde

SummaryA comparative study of various colorimetric methods for determining and detecting traces of formaldehyde has been made. Chromotropic acid and 2,7-duiydroxynaphthalene were found to be the best reagents and were subjected to a thorough study. Precise and accurate methods for determining formaldehyde using either chromotropic acid or 2,7-dihydroxynaphthalene are described. The color system produced by following the standard procedure obeys Beers law. Using chromotropic acid 0.05 μg to 2.0 μg of formaldehyde per ml can be determined quite accurately. Acrolein seems to be the only seriously interfering substance, and its interference can be much diminished by slightly modifying the standard procedure. The reagent solutions are perfectly stable.

Characterization and studies of some triethanolamine complexes of transition and representative metals

Abstract The ligand triethanolamine, 2,2′, 2″-nitrilotriethanol, forms air-stable, crystalline complexes with the bi- and the trivalent transition and representative metal salts from chromium to zinc. These compounds have not previously been characterized. They have the general formula: M (NTEH 3 ) ∗ (NTEH n ) X m where X is Cl− or CH3CO2−, and n is 2,3; m is 1,2 or 3, respectively, depending upon the charge the central metal cation, and on the value of n. Analytical and spectral data indicate that the metal is six coordinate in these compounds when the cation has unfilled 3 d subshells. These compounds are all of the high-spin type. Electronic reflectance and paper-mull spectra support the octahedral, Oh, formulation within the metallic-polyhedron, but an actual overall C2h point group for the entire monomeric group assemblage. The relative i.r. hydroxyl band intensity ratios provide direct evidence that the two axial positions in the monomers are occupied by the more basic nitrogen donor groups, and that the four equatorial positions are occupied by oxygens from the ligands. Conductance data indicate a 1:3 electrolyte in the case of Cr(NTEH3)2Cl3 and Fe(NTEH3)2Cl3; a 1:2 electrolyte in the case of Co(NTEH3)2Cl2 and Ni(NTEH3)2Cl2; and a 1:1 electrolyte in the case of Ni(NTEH3)(NTEH2)OAc, Cu2(NTEH2)2Cl2 and Cu(NTEH3)2Cl2.

Computation techniques of bjerrum's method of determination of successive formation constants

Abstract General equations for computation of the step formation constants of complexes through the determination of the degree of formation of the system and measurement of the free ligand concentration are derived. The methods of graphical solution and of solution by successive substitution are demonstrated.

Monomeric and dimeric complexes of group IIIA metal alkyls with piperidine effect of coordination on the carbon-metal bond

Abstract Complexes of the type R3Mpip and (R2Mpip′)2(pip  H NCH 2 CH 2 CH 2 CH 2 C H22; pip′  - NCH 2 CH 2 CH 2 CH 2 CH 2) have been prepared and characterized by elemental analyses, molecular weight determinations (in a few cases), i.r., mass, and NMR spectroscopy. Analysis of i.r. and NMR spectral data seems to suggest that CM bond polarity in R3Mpip is enhanced inductively by coordination. On the other hand, the exchange of an XM bond for one covalent CM bond more than compensates for this inductive enhancement due to coordination. The inductive effect seems to be more influenced by the size of the metal atom and possible participation of the d-orbitals in bonding rather than electronegativity of the metal atom.

α-Picolinic acid as a colorimetric reagent: Determination of ferrous ion

α-Picolinic acid has been used as a reagent for the colorimetric estimation of ferrous ion. The transmittancy measurements show that iron from 0.08 p.p.m. to 12 p.p.m. may be easily determined with a cell of capacity 16 ml and thickness 20 mm. The effect of time, temperature and of diverse ions on the coloured system with an absorption maximum at 440 mμ have been critically examined. The optimum range with minimum relative error is found to be in the region of 1.6 to 8 p.p.m. By jobs method the composition of the ferrous complex, which is highly soluble and stable in water, is Fe(C6H4O2N)2 with a dissociation constant in the order of 10-5. α-Picolinsaure wurde als Reagens zur kolorimetrischen Bestimmung von Ferroionen benutzt. Mit dieser Methode kann man leicht Eisen in einer Konzentration von 0.08-12‰ in einer Zelle mit einem Fassungsvermogen von 16 ml und einer Dicke von 20 mm bestimmen. Der Einfluss der Zeit, der Temperatur und verschiedener anderer Ionen auf das gefarbte System mit einem Absorptionsmaximum bei 440 mμ wurde kritisch uberpruft. Der optimale Bereich mit dem geringsten relativen Fehler wurde in dem Gebiet von 1.6-8‰ gefunden. Die Zusammensetzung des Ferrokomplcxes, der ausserordentlich gut loslich und stabil in Wasser ist, ist nach der Jobschen Methode Fe(C6H402N)2 und besitzt eine Dissoziationskonstante in der Grossenordnung von 10-5.

Spectrophotometric determination of gold with phenyl-α-pyridyl ketoxime

Abstract A method is described for the spectrophotometric determination of gold in the concentration range of 2 to 16 p.p.m. using phenyl-α-pyridyl ketoxime as the reagent. The reagent permits to detect Iμ of gold in I ml of a solution. The method is particularly free from interference by the ions with which gold is frequently associated.

Quinolinolato-complexes of aluminum, gallium and indium dialkyls

Abstract Monomeric complexes of the type R2MQ (R = Me, Et, iBu; M = Al, Ga, In; Q = quinoline-8-olate anion) have been isolated, and characterized by elemental analyses, and i.r., electronic, NMR and mass spectroscopy. Molecular weight of Et2GaQ was determined by vapor pressure osmometry. The compounds are generally yellow and crystalline. The reactivity of CM bond seemed to be much reduced compared to the CM bond in free metal alkyls. The chemical shifts in the NMR the participation of s and d orbitals of the metal atom, which in turn reduced the CM bond reactivity. Electronic spectra suggested ligand π → metal d (or s) transition. Metal-nonmetal vibrations a1 and t2 could be identified for iBu2MQ in the region 535-380 cm−1.

A catalog of retention times of a number of organic compounds

Summary The relative retention times of organic compounds on tri- m -tolyl phosphate and β,β′-oxydipropionitrile columns have been determined and tabulated. The method for the use of these tables has been suggested. Through the use of the two columns with subsequent reference to the data on the respective retention times, a wide variety of compounds can be tentatively identified.

Indirect complexometric titration of potassium, rubidium, cesium, thallium and ammonium

Abstract A titrimetric method using EDTA for the determination of potassium, rubidium, cesium, thallium and ammonium has been developed. These cations are precipitated as M 2 Ag[Co(NO 2 ) 6 ] and the blue cobalt thiocyanate complex in acetone-water mixed system is titrated with EDTA. Milligram quantities have been determined in the present work