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The experimental data for the deactivation of CO2(00°1) in CO2–CF2Cl2 and CO2–C4H4S mixtures are presented in the temperature range 323–463 K for different compositions. The relaxation rate per unit pressure (Pτ)−1 showed deviations from the linear mixture rule.

Proton spin-lattice relaxation times have been studied in CH4He, CH4Ne and CH4$z.sbnd;Ar mixtures as a function of temperature, pressure and composition. The measurements were made in the region where T1 ∞ p. The values of T 1 ϱ extrapolated to 100% inert gases were found to be proportional to T−n where n = 0.28 ± 0.08 for He, n =1.1 ± 0.1 for Ne, and n = 1.25 ± 0.09 for Ar. These values are appreciably different from the value of n obtained in pure CH4 gas. The anisotropic part of the potential is obtained from these results within the framework of Bloom-Oppenheim theory, assuming that the correlation time of the spin-rotation interaction can be approximated by the average lifetime of the molecule in the given J state and allowing for transitions between J states. The form of the potential used has a term proportional to r−12 for the repulsive part and a term proportional to r−7 for the attractive part, as derived by Buckingham for the interaction between a spherical and a tetrahedral molecule. The latter depends on the molecular hyperpolarizability A, which describes the distortion of the molecule due to an external field and field gradient. The hyperpolarizability obtained from the experimental data is comparable with the theoretical estimates.

Proton spin-lattice relaxation times, T1, have been measured in H2–Ar and H2–N2 gas mixtures as a function of density (10 1 data obtained by Foster and Rugheimer and by Williams in these mixtures below 300 K have been analysed using the Bloom–Oppenheim theory. Models for intermolecular potentials to explain the T1 data have been proposed. It is found that the relative anisotropy in the attractive part of the intermolecular potential which fits the T1 data best compares well with that evaluated using polarizability data.

Proton spin‐lattice relaxation times were measured in C2H4 and mixtures of C2H4 with He, A, and N2 as a fuction of density, composition, and temperature (300–600 K) in the region where T1∝ρ using a 30 MHz spin‐echo spectrometer. The values of T1/ρ for infinite dilution of C2H4, (T1/ρ)C2H4–X were found to be proportional to T−n, where n=1.43 for C2H4–C2H4, 0.54 for C2H4–He, 1.18 for C2H4–A, and 1.25 for C2H4–N2. These data were analyzed, using Bloom–Oppenheim theory and assuming that the correlation time of the spin−rotation interaction in a J state is equal to the lifetime of a molecule in that J state, to obtain information on the spin‐rotation coupling constant, up to a constant, as well as the intermolecular anisotropic interactions responsible for spin‐lattice relaxation in these systems.

The proton spin—lattice relaxation time T 1 was measured as a function of density in gaseous methyl chloride in the vicinity of T 1 minimum at 298 K. The experimental data were interpreted to obtain the effective value of the spin—rotation interaction constant for proton spins and the effective cross section for molecular reorientation.

Proton spin-lattice relaxation times were measured in C2H2 and mixtures of C2H2 with He, Ar, and N2 as a function of density, composition, and temperature (300–600 K) in the region where T1 ∞ ϱ with a 30 MHz spin-echo spectrometer using phase-coherent detection. The values of T 1 ϱ for infinite dilution of C2H2, ( T 1 ϱ ) C 2 H 2 −X , were found to be proportional to T−n where n = 1.42 for C2H2C2H2, 0.69 for C2H2He, 1.14 for C2H2Ar, and 1.36 for C2H2N2. These data were used to obtain the parameters in the anisotropic intermolecular potential within the framework of Bloom-Oppenheim theory and assume that the correlation time of the spin-rotation interaction in a J state is equal to the lifetime of a molecule in that J state. Lennard-Jones (12-6) potential and modified Buckingham (exp-6) potential were used for the isotropic part. Relative anisotropy in the attractive r−6 term and the quadrupole moment of C2H2 molecule obtained from these two model potentials were compared with the calculated value from the polarizability data and the recommended value of C2H2, respectively.

1. Cacotheline has previously been employed as a colorimetric reagent for the detection of Sn +2 and V +3 ions. The present investigation covers its use as a reagent for the detection of Fe +2 and Fe +3 ions. 2. Fe +2 ions give a pink colour with a solution of cacotheline at a pH lying between 1.48 and 4.58 in the presence of a sufficient concentration of sodium oxalate, which serves to bind the Fe +3 ions by complex formation. At a pH below 1.24, only a very light pink colour is produced and this develops slowly. When the pH of the solution is about 5.2, a blue colour is obtained. The limit of identification is 1.5 γ and the concentration limit is 1 : 40,000 of Fe +2 . While testing for Fe +2 at very low concentration, it is necessary to employ a very dilute solution of cacotheline (0.025%), while for solutions of higher concentrations saturated cacotheline solution (about 0.25%) is recommended. A detailed investigation has been made concerning the conditions determining the stability of the pink colour. 3. It has also been observed that sodium malonate, sodium citrate, sodium malate, sodium tartrate and sodium lactate are effective as complexing agents for binding Fe +3 ions. 4. Orthophosphate has not been found effective as a complexing agent under the conditions adopted, while pyrophosphate and metaphosphate have been found effective. 5. Fe +3 ions are reduced to Fe +2 by exposure to sunlight or the light from a Philip's Repro lamp in the presence of the appropriate buffer solution and sodium oxalate.

The dependence of the proton T 1 in dilute CH 4 gas on temperature at constant density is appreciably different than for CH 4 in helium gas. This difference can give information on the CH 4 - CH 4 and CH 4 - He intermolecular potentials.

Rate constants for the transfer of energy from CO2(00°1) to ethane and n‐butane were measured using the laser induced fluorescence technique. The large magnitudes and the negative temperature dependence of the energy transfer rates indicate that near‐resonant energy transfer processes caused by long range forces are responsible for the deactivation of the asymmetric stretching mode of CO2. It is shown that the combination bands in the alkanes are likely to receive the energy from CO2(00°1). Using Sharma–Brau theory with Tam’s modification and our experimental results, the square of the transition dipole matrix elements of ν3+ν6 and ν9+ν11 bands of ethane are estimated. At any given temperature in the range 300–730 °K, the energy transfer cross section was found to increase linearly with n of CnH2n+2. It is suggested that the absorption intensity of the combination bands of the alkanes also increases linearly with n in the spectral range 2300–2400 cm−1.