A simple dewar type calorimeter has been constructed to determine the enthalpy of mixing in dilute concentration range and its performance checked by determining the heats of mixing of cyclohexane (l)-n-hexane (2) and ethanol (1)n-hexane (2) systems. The heats of mixing ofn-butylamine withn-hexane and ethanol have been determined at 30° C. The enthalpy of ethanol-butylamine complex calculated by a thermochemical cycle was found to be-40.3 kJ/mol.

The heats of mixing ofn-butyl amine with methanol andn-propanol have been determined at 30° C and the enthalpies of alcohol-amine complex formation have been calculated by thermochemical cycle. The enthalpies of complex formation of butyl amine with methanol andn-propanol were found to be-44.3 kJ/mole and-39.4 kj/mole respectively. The heats of mixing of synthetically prepared 1:1 molar mixtures of n-butyl amine with methanol, ethanol andn-propanol withn-hexane have also been determined at 30° C. The enthalpy of amine-alcohol complexes was obtained from the partial molar heats of dissociation of the complexes inn-hexane. The values agree with those obtained by the thermochemical cycle method.

The excess free energy, enthalpy and entropy of mixing of isomeric butanols withn-heptane determined at 55°C were found to be positive due to the breaking of hydrogen bonds. In the case ofn-butanol the excess entropy was negative beyond the concentration rangex₂>0.4. The data on excess free energy and enthalpy of mixing could be well represented by the Redlich-Kister equation. An attempt to calculate excess enthalpy from temperature dependence of excess free energy for iso and sec-butanol systems has been made. The results are discussed in the light of the idealised model.

The enthalpy of complex formation between different isomers of butylamine and butylalcohol was determined at 30°C by obtaining the partial molar enthalpy of dissociation of 1∶1 complexes inn-hexane. In both seriesviz. normal amine with isomeric alcohols and normal alcohol with isomeric amines, the enthalpy of complex formation showed the same trend ast>n>iso>sec.

The trend in normal-normal, normal-tertiary, tertiary-tertiary and secondary-secondary omplexes was ast−n>n−n>t−t> sec-sec. Both these trends were explained in terms of steric and electromeric effects.

Enthalpies of complex formation (ΔH_c) of dibutyl and tributyl amines with the four isomeric butanols were determined at 30°C. The present data were compared with the previous data on isomeric butanols with monobutyl amine complexes. The ΔH_c in the case ofn-alcohol has been found to decrease by about 4·0±0·4 kJ/mole on replacement of each hydrogen atom of the NH₂ group. The branching of the butyl chain, also, decreases the strength of the complex due to steric hindrance.

The excess volume of mixing for 1-aminobutane, 2-aminobutane, 1-amino-2-methylpropane and 2-amino-2-methylpropane with chloroform were determined at 30° by the density method. TheV^E were negative for all the systems and showed the following order: 2-amino-2-methylpropane>2-aminobutane>1-amino-2-methylpropane>1-aminobutane. The negativeV^E were attributed to complex formation between the amine and chloroform molecules owing to H bonding, while the particular trend was attributed to the decreasing degree of self-association of amine isomers.

Enthalpies of mixing of isomeric butylamine with chloroform were determined at 30°C by a Calvet-type microcalorimeter. The system showed highly exothermic behaviour due to hydrogen-bonded complex formation on mixing. The enthalpies of complex formation were calculated by means of a thermo-chemical cycle and the values vary from 1-aminobutane to 2-amino-2-propane complexes.

The enthalpies of mixing of four isomeric butanols with di-n-butyl ether were determined at 30°C by a Calvet type microcalorimeter. All the four systems showed endothermic behaviour. The enthalpies of complex formation were calculated by the thermochemical cycle. The strength of H-bonding decreases in the order l-butanol, l-methyl-1-propanol, 2-methyl-2-propanol, 2-butanol. The results are explained on the basis of a steric effect on interaction.

The excess volumes of four isomeric butanols with di-n-butyl ether were determined at 30°C. The isomeric effect was distinctly observed in the excess volume profiles. 1-Butanol and 2-methyl-l-propanol systems exhibited negative excess volumes throughout the concentration range. The 2-butanol system had positive excess volumes up to 0.9 mol fraction of alcohol after which it became negative, while the 2-methyl-2-propanol system exhibited positive excess volumes throughout the concentration range.

The enthalpies of mixing of four isomeric butanols with acetonitrile were determined at 30°C by a Calvet type microcalorimeter. All the four systems showed endothermic behaviour. The enthalpies of hydrogen bonded complex formation were determined by means of a thermochemical cycle. 1-butanol formed a stronger bonding (−13kJ/mole) than the other three isomers (−11.20kJ/mole). The strength of the H-bond of alcohol with C ≡ N is much less than that with C-N.