Dissociation constants of the ampholyte glycine in 50 mass % methanol-water from 5 to 55°C,with related thermodynamic quantities

The two thermodynamic dissociation constants of glycine at 11 temperatures from 5 to 55°C in 50 mass % methanol-water mixed solvent have been determined from precise emf measurements with hydrogen-silver bromide electrodes in cells without liquid junction. The first acidic dissociation constant (K ₁)for the process HG⁺H⁺+G^± is expressed as a function ofT(^oK) by the equation pK ₁ = 2043.5/T – 9.6504 + 0.019308T. At 25°C, pK ₁is 2.961 in the mixed solvent, as compared with 2.350 in water, with H°=1497 cal-mole^–1, G°=4038 cal-mole^–1, S°=–8.52 cal-°K^–1-mole^–1, and C _p ^o =–53 cal-°K^–1-mole^–1. The second acidic dissociation constant (K ₂)for the process G^±H⁺+G^– over the temperature range studied is given by the equation pK ₂ = 3627.1/T – 7.2371 + 0.015587T. At 25°C, pK ₂is 9.578 in MeOH–H₂O as compared with 9.780 in water, whereas H° is 10,257 cal-mole^–1, G° is 13,063 cal-mole^–1, S° is –9.41 cal-°K^–1-mole^–1, and C _p ^o is –43 cal-°K^–1-mole^–1. The protonated glycine becomes weaker in 50 mass % methanol-water, whereas the second dissociation process becomes stronger despite the lower dielectric constant of the mixed solvent (=56.3 at 25°C).     

Micro-Raman investigations of myelins in aerosol-OT/water system

Surfactant outgrowth during dissolution as myelin figures, which happens on contact with water, is of prime importance in emulsification and detergency. Micro-Raman investigation of different lyotropic phases formed during dissolution of aerosol-OT (bis 2-ethylhexyl sulfosuccinate) in water during myelin formation reveals the flexible arrangement of the surfactant bilayers in myelin. The conformation around CC-CS bond and the hydrocarbon chains of aerosol-OT in the different liquid crystalline phases were identified from the fingerprints of CC-CS stretching, C-C stretching, C-H bending, and stretching frequencies. Existence of mixture of trans and gauche conformations around CC-CS bond and that of the hydrocarbon chains in myelin supports the fluid nature of bilayers by which it is made. Similar conformations of hydrocarbon chains in lamellar phase and in myelin support the concept of myelins being rolled up lamella. The observations are in line with the disorderness of the hydrocarbon chains in the bilayers of phospholipids that has been reported earlier. From the C-C stretching frequencies at the root of myelins, the kinked structure of the hydrocarbon chain is identified, and loose packing of molecules which would facilitate water transport across membranes is evident.     

Highly efficient water promoted allylation and propargylation of arylepoxides via rearrangement-carbonyl addition

A simple and highly efficient one-pot procedure for allylation and propargylation of arylepoxides has been developed. A combination of SnCl₂ and catalytic Pd(0) or Pd(II) promotes the reaction of organic halides and epoxides in DMSO with controlled water addition, leading to the regioselective formation of the corresponding homoallyl and homopropargyl alcohols in good yields.     

Evaluating the Frechet derivative of the matrix exponential

LetM _n denote the space ofn×n matrices. GivenX, ZM _n define

Energy dependence of the fast fragment of the target nucleus in high energy hadron-nucleus interaction

This paper presents an extensive study on the dependence of the mean number of the fast fragment of the target nucleus n _g on the incident beam energy in proton-nucleus interaction in emulsion in the range 6·2E ₀400 GeV/c. It has been observed that n _g decreases in the range 6·2E ₀200 GeV/c, then increases and attains an approximately steady value up to 400 GeV/c. It is very difficult to explain this behaviour with the help of the existing nuclear production models.The author would like to thank Prof A. J. Herz (CERN), Prof. K. D. Tolostov (Dubna, U.S.S.R.), Prof. P. L. Jain (State University of New York, U.S.A.), Prof. G. Giacomelly (Italy) for kindly supplying the exposed emulsion plates.     

Thermal noise in Hg0.795Cd0.205Te detectors for large biasing fields

Thermal noise in Hg_0.795Cd_0.205Te detectors is estimated for large biasing fields at a lattice temperature of 77 K, by computing the correlation functions of the velocity fluctuations with the Monte Carlo technique. The noise temperature for current components transverse to the field is almost independent of the field, but that corresponding to the parallel component increases by a factor of about 1.3 at 50 V/cm and by a factor of 3.0 at 300V/cm. The thermal noise voltage for a detector of 85 resistance increases from 0.6nV/Hz^1/2 at low biasing fields to about 3nV/Hz^1/2 at a field of 300 V/cm. The noise power is also found to remain constant up to about 75 GHz, and it decreases thereafter by a factor of 0.25 for doubling of the frequency.     

New products

Summary An efficient and economical GC method for rapid determination of FAMEs in rapeseed-mustard is described. The seeds were transmethylated with acetylchloride, using microwave heating and separation achieved on a 3 m column packed with a mixture of 2% SP-2300 and 3% SP-2310 on Chromosorb ‘W’. The method is compared with the conventional heating method and extended efficiently for half-seed analysis. The fatty acid composition of the FAMEs mixtures prepared by both methods was similar with highly significant correlation coefficients (P<0.001).