Carbon Tetrachloride Vapor Research Articles

The Concentration of Isotopes by the Evaporative Centrifuge Method

The air-driven vacuum-type tubular centrifuge has been used for the concentration of the isotopes of chlorine by the "evaporative" centrifuge method. The separations obtained were about the same as predicted by the theory provided the experimental conditions approximately conformed to the assumptions of the theory. With a steel tube 11\ensuremath{''} long and 3\ensuremath{''} inside diameter, containing baffles to prevent remixing, and spinning at 1060 r.p.s., carbon tetrachloride vapor could be withdrawn from the axis at the rate of 3.2 grams per minute without decreasing the separation factor. This separation factor for chlorine, which at any instant is the ratio of the concentrations of the light to heavy isotopes at the axis, divided by the same ratio at the periphery, was 1.025 in the above case. It is believed that the method is practical in the case of the heavier elements.

Diffraction of X-Rays and Electrons by Carbon Tetrachloride Vapour

RECENT electron-diffraction investigations1 of the molecular structure of gaseous carbon tetrachloride give values of the interatomic distances, which are appreciably lower than those obtained in earlier electron-diffraction measurements and those obtained by Bewilogua2 from X-ray photographs. This discrepancy of about 4 per cent is so important that it cannot be explained by the probable errors given by the authors. As, moreover, carbon tetrachloride is generally used as a standard substance for testing the apparatus, it seemed to us to be of interest to compare X-ray and electron-diffraction results from as wide a field as possible with the corresponding theoretical calculation, using in both cases the most trustworthy experimental methods.

The Red CN Band System

Rotational Structure of red CN bands. The rotational structure of the (4,1), (5,2), (6,1), (6,2), (7,2), (7,3) and (8,3) bands of this system is measured on plates from the first order of a 21-foot grating. To excite the spectrum, carbon tetrachloride vapor was mixed with active nitrogen. The lines of each band are arranged in eight branches, giving a structure characteristic of a $^{2}\ensuremath{\Pi}\ensuremath{\rightarrow}^{2}\ensuremath{\Sigma}$ transition in which the spin doubling in $^{2}\ensuremath{\Sigma}$ is small. Missing lines show the $^{2}\ensuremath{\Pi}$ state to be inverted. Good agreement is obtained for the constants of the lower state with those of the violet CN system. The rotational constants of the $^{2}\ensuremath{\Pi}$ state are: $A=\ensuremath{-}52.2$ ${\mathrm{cm}}^{\ensuremath{-}1}$, ${B}_{v}=1.6990\ensuremath{-}0.01746 (v+\frac{1}{2})$ ${\mathrm{cm}}^{\ensuremath{-}1}$, ${D}_{v}=\ensuremath{-}[6.133+0.0127 (v+\frac{1}{2})]\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ ${\mathrm{cm}}^{\ensuremath{-}1}$, ${I}_{e}=16.28\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}40}$ g ${\mathrm{cm}}^{2}$, ${r}_{e}=1.236\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$ cm. The $^{2}\ensuremath{\Pi}$ terms are represented accurately by the Hill and Van Vleck formula. Microphotometer measurements of photographic densities in the 8,3 band are given, and agree qualitatively with the theory. They show the $^{2}\ensuremath{\Pi}_{\frac{3}{2}}\ensuremath{\rightarrow}^{2}\ensuremath{\Sigma}$ band to be stronger than the $^{2}\ensuremath{\Pi}_{\frac{1}{2}}\ensuremath{\rightarrow}^{2}\ensuremath{\Sigma}$ band.Spin doubling and $\ensuremath{\Lambda}$-doubling. A rough evaluation of the difference ${{F}_{1}}^{\ensuremath{'}\ensuremath{'}}(K)\ensuremath{-}{{F}_{2}}^{\ensuremath{'}\ensuremath{'}}(K)={\ensuremath{\gamma}}_{0}(K+\frac{1}{2})$ is possible, and gives ${\ensuremath{\gamma}}_{0}=+0.0071 \mathrm{and} 0.0082$ and for ${v}^{\ensuremath{'}\ensuremath{'}}=3 \mathrm{and} 2$, respectively. For the states ${v}^{\ensuremath{'}}=4, 5 \mathrm{and} 8$, the $\ensuremath{\Lambda}$-doubling is regular, and of the form recently discussed by Mulliken and Christy. We find ${p}_{0}=0.00621, 0.00853, 0.01872$, ${q}_{0}=\ensuremath{-}0.000252, \ensuremath{-}0.000365 \mathrm{and} \ensuremath{-}0.000435$ for ${v}^{\ensuremath{'}}=4, 5 \mathrm{and} 8$.Perturbations. Three strong perturbations are found in ${v}^{\ensuremath{'}}=6$, in ${T}_{1c}$ at $J=13\frac{1}{2}$, in ${T}_{1d}$ at $J=25\frac{1}{2}$ and in ${T}_{2d}$ at $J=27\frac{1}{2}$. These are exactly as expected theoretically from the three corresponding perturbations found in the violet system by Rosenthal and Jenkins, and from an extrapolation of the unperturbed levels. An anomalous $\ensuremath{\Lambda}$-doubling in ${^{2}\ensuremath{\Pi}_{\frac{1}{2}}}^{(7)}$ is explained as a perturbation, with the difference that here the perturbing levels of ${^{2}\ensuremath{\Pi}_{\frac{1}{2}}}^{(7)}$ and ${a}^{2}{\ensuremath{\Sigma}}^{(12)}$ do not cross, but merely approach closely.Vibrational structure. From measurements of the ${R}_{2}$ heads of 17 other bands, and correction to origins, the following expression is obtained for band origins: $\ensuremath{\nu}=11,043.20+1788.66 ({v}^{\ensuremath{'}}+\frac{1}{2})\ensuremath{-}12.883 {({v}^{\ensuremath{'}}+\frac{1}{2})}^{2}\ensuremath{-}2068.79 ({v}^{\ensuremath{'}\ensuremath{'}}+\frac{1}{2})+13.176 {({v}^{\ensuremath{'}\ensuremath{'}}+\frac{1}{2})}^{2}.$ Perturbations of the band origins by 1 or 2 ${\mathrm{cm}}^{\ensuremath{-}1}$ occur for ${v}^{\ensuremath{'}}=6 \mathrm{and} 7$, and are evidently of similar origin to the rotational perturbations in these states. The vibrational numbering used here for the $^{2}\ensuremath{\Pi}$ state is that of Asundi and Ryde. This numbering, hitherto in doubt, has now been definitely established by a comparison of the observed vibrational intensity relations with those predicted by the wave mechanics with the method of Condon.

The Red CN Band System

Rotational Structure of red CN bands. The rotational structure of the (4,1), (5,2), (6,1), (6,2), (7,2), (7,3) and (8,3) bands of this system is measured on plates from the first order of a 21-foot grating. To excite the spectrum, carbon tetrachloride vapor was mixed with active nitrogen. The lines of each band are arranged in eight branches, giving a structure characteristic of a $^{2}\ensuremath{\Pi}\ensuremath{\rightarrow}^{2}\ensuremath{\Sigma}$ transition in which the spin doubling in $^{2}\ensuremath{\Sigma}$ is small. Missing lines show the $^{2}\ensuremath{\Pi}$ state to be inverted. Good agreement is obtained for the constants of the lower state with those of the violet CN system. The rotational constants of the $^{2}\ensuremath{\Pi}$ state are: $A=\ensuremath{-}52.2$ ${\mathrm{cm}}^{\ensuremath{-}1}$, ${B}_{v}=1.6990\ensuremath{-}0.01746 (v+\frac{1}{2})$ ${\mathrm{cm}}^{\ensuremath{-}1}$, ${D}_{v}=\ensuremath{-}[6.133+0.0127 (v+\frac{1}{2})]\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ ${\mathrm{cm}}^{\ensuremath{-}1}$, ${I}_{e}=16.28\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}40}$ g ${\mathrm{cm}}^{2}$, ${r}_{e}=1.236\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$ cm. The $^{2}\ensuremath{\Pi}$ terms are represented accurately by the Hill and Van Vleck formula. Microphotometer measurements of photographic densities in the 8,3 band are given, and agree qualitatively with the theory. They show the $^{2}\ensuremath{\Pi}_{\frac{3}{2}}\ensuremath{\rightarrow}^{2}\ensuremath{\Sigma}$ band to be stronger than the $^{2}\ensuremath{\Pi}_{\frac{1}{2}}\ensuremath{\rightarrow}^{2}\ensuremath{\Sigma}$ band.Spin doubling and $\ensuremath{\Lambda}$-doubling. A rough evaluation of the difference ${{F}_{1}}^{\ensuremath{'}\ensuremath{'}}(K)\ensuremath{-}{{F}_{2}}^{\ensuremath{'}\ensuremath{'}}(K)={\ensuremath{\gamma}}_{0}(K+\frac{1}{2})$ is possible, and gives ${\ensuremath{\gamma}}_{0}=+0.0071 \mathrm{and} 0.0082$ and for ${v}^{\ensuremath{'}\ensuremath{'}}=3 \mathrm{and} 2$, respectively. For the states ${v}^{\ensuremath{'}}=4, 5 \mathrm{and} 8$, the $\ensuremath{\Lambda}$-doubling is regular, and of the form recently discussed by Mulliken and Christy. We find ${p}_{0}=0.00621, 0.00853, 0.01872$, ${q}_{0}=\ensuremath{-}0.000252, \ensuremath{-}0.000365 \mathrm{and} \ensuremath{-}0.000435$ for ${v}^{\ensuremath{'}}=4, 5 \mathrm{and} 8$.Perturbations. Three strong perturbations are found in ${v}^{\ensuremath{'}}=6$, in ${T}_{1c}$ at $J=13\frac{1}{2}$, in ${T}_{1d}$ at $J=25\frac{1}{2}$ and in ${T}_{2d}$ at $J=27\frac{1}{2}$. These are exactly as expected theoretically from the three corresponding perturbations found in the violet system by Rosenthal and Jenkins, and from an extrapolation of the unperturbed levels. An anomalous $\ensuremath{\Lambda}$-doubling in ${^{2}\ensuremath{\Pi}_{\frac{1}{2}}}^{(7)}$ is explained as a perturbation, with the difference that here the perturbing levels of ${^{2}\ensuremath{\Pi}_{\frac{1}{2}}}^{(7)}$ and ${a}^{2}{\ensuremath{\Sigma}}^{(12)}$ do not cross, but merely approach closely.Vibrational structure. From measurements of the ${R}_{2}$ heads of 17 other bands, and correction to origins, the following expression is obtained for band origins: $\ensuremath{\nu}=11,043.20+1788.66 ({v}^{\ensuremath{'}}+\frac{1}{2})\ensuremath{-}12.883 {({v}^{\ensuremath{'}}+\frac{1}{2})}^{2}\ensuremath{-}2068.79 ({v}^{\ensuremath{'}\ensuremath{'}}+\frac{1}{2})+13.176 {({v}^{\ensuremath{'}\ensuremath{'}}+\frac{1}{2})}^{2}.$ Perturbations of the band origins by 1 or 2 ${\mathrm{cm}}^{\ensuremath{-}1}$ occur for ${v}^{\ensuremath{'}}=6 \mathrm{and} 7$, and are evidently of similar origin to the rotational perturbations in these states. The vibrational numbering used here for the $^{2}\ensuremath{\Pi}$ state is that of Asundi and Ryde. This numbering, hitherto in doubt, has now been definitely established by a comparison of the observed vibrational intensity relations with those predicted by the wave mechanics with the method of Condon.

The sorption of carbon tetrachloride at low pressures by activated charcoals. Part III.— isosteres —discussion

The essential ain of these measurments of the dependence of equilibrium pressure on temperature for charcoals with definite charges of carbon tetrachloride was the calculation of heats of sorption by the Clapeyron-Clausius equation. This was effected by plotting each isostere in the form of the logarithm of the pressure against the reciprocal of the absolute temperature, the slope of the resulting linear curve measuring the molecular heat of sorption. A few points regarding experimental detail will be briefly referred to. The number of pressure-temperature measurements made on each charged charcoal sample varied between 3 and 13. As each pressure measurement involved opening up the charcoal container to the pressure gauge and connecting tubes (of total volume about 330 c. C.), this space was, prior to turning the container tap, charged with carbon tetrachloride vapour from the supply bulb until its pressure was near to (although still below) the pressure which it was estimated the charged charcoal would exert at the temperature in question. In this way, loss of sorbate from the charcoal during the set of measurements, which might have proved appreciable without this precaution, was reduced to a quite negligible figure.

Preliminary Report on Carbon Tetrachloride Vapor as a Delousing Agent

Preliminary Report on Carbon Tetrachloride Vapor as a Delousing Agent