scholarly journals The rate of evaporation of droplets. III. Vapour pressures and rates of evaporation of straight-chain paraffin hydrocarbons

1949 ◽  
Vol 198 (1053) ◽  
pp. 239-251 ◽  
Keyword(s):  
Diffusion Coefficients ◽  
The Self ◽  
Straight Chain ◽  
Evaporation Coefficient ◽  
A Value ◽  
Evaporation Of Droplets ◽  
Hydrocarbon Molecules ◽  
Rate Of Evaporation ◽  
Latent Heats ◽  
And Diffusion

The vapour pressures, latent heats of vaporization and fusion and diffusion coefficients of the vapours in air, have been determined at 15 to 40° C, by a combination of Knudsen’s vapour-pressure technique and studies on the rate of evaporation of drops and solid beads, for n -C 16 H 34 , n -C 17 H 36 and n -C 18 H 38 . The rates of evaporation of drops and solid beads agree with the previously published theory, and lead to a value of unity for the evaporation coefficient. A new experimental method is described for determining the self-cooling on evaporation of a drop. The bearing of the results on the size and shape of hydrocarbon molecules is discussed.

The rate of evaporation of droplets. V. Evaporation characteristics of some branched-chain hydrocarbons and a straight-chain fluorocarbon

1951 ◽  
Vol 206 (1084) ◽  
pp. 65-72 ◽  
Keyword(s):  
Diffusion Coefficients ◽  
Vapour Pressure ◽  
Straight Chain ◽  
Evaporation Coefficient ◽  
Evaporation Of Droplets ◽  
Branched Chain ◽  
Rate Of Evaporation ◽  
Latent Heats ◽  
Heats Of Vaporization

The vapour pressures, latent heats of vaporization and densities have been determined for (C 7 H 15 ) 2 CH and (C 10 H 21 ) 3 CH at 25 to 40° C, and the rate of evaporation of droplets has been studied at a range of air pressures at 25 to 35º C. Diffusion coefficients in air and collision radii have been calculated. The evaporation coefficient is unity. For n -C 16 F 34 the vapour pressure and heat of sublimation have been determined at 15 to 30° C, and the values of diffusion coefficients and collision areas have been determined from the evaporation characteristics of solid beads. A comparison has been made of the data for straight- and branchedchain hydrocarbons, and for straight-chain fluoro- and hydrocarbons.

scholarly journals The rate of evaporation of droplets. Evaporation and diffusion coefficients, and vapour pressures of dibutyl phthalate and butyl stearate

1946 ◽  
Vol 186 (1006) ◽  
pp. 368-390 ◽  
Keyword(s):  
Diffusion Coefficients ◽  
Atmospheric Pressure ◽  
Dibutyl Phthalate ◽  
Droplet Evaporation ◽  
Medium Size ◽  
Good Accordance ◽  
Butyl Stearate ◽  
Rate Of Evaporation ◽  
Low Pressures ◽  
And Diffusion

The rate of evaporation of drops of dibutyl phthalate and butyl stearate of radius approx. 0.5 mm. has been studied by means of a microbalance over a range of atmospheric pressures down to approx. 0*1 mm. of mercury. Wide departures from Langmuir’s evaporation formula were found to occur at these low pressures, but results are in good accordance with the theory of droplet evaporation advanced by Fuchs which hitherto has not been tested experimentally. This experimental verification of Fuch’s theory for droplets of medium size evaporating at low pressures shows that the theory can be applied to the evaporation of very small drops at atmospheric pressure. The vapour pressures of the above liquids have been measured by Knudsen’s method and the evaporation and diffusion coefficients calculated fro n the experimental data.

scholarly journals The accommodation coefficient and the evaporation coefficient of water

1935 ◽  
Vol 149 (866) ◽  
pp. 104-116 ◽  
Keyword(s):  
Liquid Surface ◽  
Pure Water ◽  
Direct Calculation ◽  
Accommodation Coefficient ◽  
Evaporation Coefficient ◽  
Saturated Vapour Pressure ◽  
Saturated Vapour ◽  
A Value ◽  
Temperature Equilibrium ◽  
Rate Of Evaporation

Previous experiments have already indicated that the maximum rate of evaporation of water into a vacuum is not so great as would be expected theoretically. The ratio of the experimental to the theoretical rate is defined as the evaporation coefficient f and has been found to have a value of about 0⋅04 for pure water at temperatures about 0º C. This result would indicate that, of the vapour molecules striking the liquid surface, about 96% must return to the vapour without entering the liquid. It is therefore of interest to enquire whether these vapour molecules attain temperature equilibrium with the surface or rebound at once before this equilibrium can be established. In the present paper experiments are described in which vapour molecules are incident on a liquid surface which is at a temperature lower than that of the vapour itself and the itself and the energy transferred to the surface by the vapour molecules is measured. If α, the accommodation coefficient, is defined as usual as the ratio of the energy actually transferred to the maximum possible transfer, it is found that for water at 10º C— α= 1⋅0 f = 0⋅036 so that, while only a very small fraction of the vapour molecules enter the liquid, all of them reach temperature equilibrium with the surface before re-evaporating into the vapour. Method If a drop of water is allowed to form on a glass tip in a vessel maintained at a pressure ( p ) which is lower than the saturated vapour pressure corresponding to the temperature of the drop, steady evaporation takes place from the surface of the latter throughout the period of its formation. This evaporation cools the surface. When the drop is fully formed it falls from the tip and may be collected and the drop weight determined. The surface tension can be deduced therefrom and hence the surface temperature may be obtained. This data makes possible the direct calculation of f as follows.

scholarly journals Studies on Transformations of Hemophilus influenzae

1961 ◽  
Vol 44 (6) ◽  
pp. 1229-1239 ◽  
Author(s):  
Sol H. Goodgal ◽  
Roger M. Herriott
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Sedimentation Coefficient ◽  
Close Correlation ◽  
Erythromycin Resistance ◽  
Hemophilus Influenzae ◽  
A Value ◽  
Transforming Activity ◽  
Separation Cell ◽  
And Diffusion

The sedimentation and diffusion coefficients have been determined for Hemophilus influenzae transforming activity and DNA using P32-labeled DNA. The methods employed the Spinco fixed boundary separation cell for measurements of the sedimentation coefficient and the Northrop-Anson diffusion cell to determine the diffusion coefficient. There was a very close correlation between the amount of DNA and transforming activity sedimented or diffused. The sedimentation coefficient (s20°), for both biological activity and DNA was 27 and the diffusion coefficient (D20°) 1 x 10-8 cm2/sec. The molecular weight calculated from these coefficients gave a value of 16 million. There was no difference in the sedimentation coefficients for the two unlinked markers, streptomycin and erythromycin resistance, and the diffusion coefficients for single markers or the linked markers, streptomycin and cathomycin, were the same.

Rates of evaporation VI. The vapour pressure and rate of evaporation of potassium chloride

1953 ◽  
Vol 217 (1131) ◽  
pp. 508-523 ◽  
Keyword(s):  
Potassium Chloride ◽  
Single Crystals ◽  
Latent Heat ◽  
Vapour Pressure ◽  
Evaporation Coefficient ◽  
Heat Of Vaporization ◽  
A Value ◽  
Rate Of Evaporation ◽  
Latent Heat Of Vaporization ◽  
Effusion Method

The vapour pressure of potassium chloride has been determined by an effusion method at 438 to 597°C and is given by log 10 p mm of Hg = – 11310/ T +10·451; the latent heat of vaporization over this range is 51720 ± 500 cal mole -1 ,giving a value of 54430 + 500 cal mole -1 at 0°K. The rate of evaporation of single crystals has been determined at 399 to 515°C. The evaporation coefficient for (100), (111) faces is 0·72 ± 0·015 (independent of temperature). A crystal with (110) and (100) faces gave an evaporation coefficient of 0·63 (independent of temperature), suggesting that the evaporation coefficient for the (110) face is 0·56.

scholarly journals Aggregation Behavior of 6-Isocassine and N-Methyl-6-Isocassine: Insights into the Biological Mode of Action of Lipid Alkaloids

2016 ◽  
Vol 11 (11) ◽  
pp. 1934578X1601101
Author(s):  
Luis Reina ◽  
Gualberto Bottini ◽  
Zohra Bennadji ◽  
Vittorio Vinciguerra ◽  
Fernando Ferreira ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Diffusion Coefficients ◽  
Mode Of Action ◽  
Aggregation Behavior ◽  
The Self ◽  
Self Diffusion ◽  
And Diffusion

The aggregation behavior of 6-isocassine and N-methyl-6-isocassine, two piperidin-3-ol alkaloids isolated respectively from the barks of Prosopis nigra and P. affinis, was investigated using a combination of NOE experiments and diffusion measurements in solvents of varying polarity and hydrogen bonding capacity. While the NOE enhancements for N-methyl-6-isocassine are positive, regardless of the solvent, those for 6-isocassine shift from negative to positive when going from chloroform- d to methanol- d 4 solution. In addition, despite the self-diffusion coefficients of both compounds being virtually identical in methanol- d 4, N-methyl-6-isocassine diffuses nearly twice as fast as the non-methylated alkaloid in chloroform- d. The changes in rotational and translational dynamics observed between solvents for 6-isocassine suggest that the molecule forms dimeric head-to-head aggregates in non-polar aprotic environments, a behavior that could help explain the biological mode of action that has been proposed for this type of alkaloids.

The rate of evaporation of droplets. II. The influence of changes of temperature and of the surrounding gas on the rate of evaporation of drops of di-n-butyl phthalate

1949 ◽  
Vol 198 (1053) ◽  
pp. 226-239 ◽  
Keyword(s):  
Diffusion Coefficient ◽  
Vapour Pressure ◽  
Experimental Error ◽  
Spherical Shape ◽  
Evaporation Coefficient ◽  
Evaporation Of Droplets ◽  
Loss Of Mass ◽  
Butyl Phthalate ◽  
Rate Of Evaporation ◽  
Heat Of Evaporation

The vapour pressure of di- n -butyl phthalate has been determined by Knudsen’s method at 15 to 40° C and is given by log ' 10 p (in microns) = — 4790/ T + 14-502. The latent heat of evaporation is 21,910 cal. per mole. Rates of effusion through a small hole in the presence of pressures of air 2 to 0 01 cm. have also been determined and shown to conform to the equation rate of loss of mass = A|(B + P) , where A and B are constants. The rate of evaporation of drops of di- n -butyl phthalate about 0-5 mm. in radius has been determined at 15 to 40° C, in air at pressures 20 to 0-01 cm. and in hydrogen at 19.90° C and Freon 12 (CC1 2 F 2 ) at 19.90 and 30.00° C and has been accounted for theoretically. Within the experimental error the evaporation coefficient is unity at all temperatures. The diffusion coefficient D in air at 76 cm. varies from 0.0341 to 0.0473 for a temperature variation 15 to 40° C, D being proportional to T 3 . The diffusion coefficient in H 2 at 19*90° C is 0*153 for 76 cm., and for diffusion in Freon 12 at 76 cm. is 0.0126 at 19.90° C and 0.0140 at 30.00° C. The collision radius of di-n-butyl phthalate is 4.45 A as determined from the experiments in air at 19*90° C and the sum of the radii of di-n-butyl phthalate and air molecules is proportional to T ~$. From the experiments in hydrogen the collision radius of di- n -butyl phthalate is 4.68 Å at 19.90° C and from the experiments using Freon 12, 5.24 Å at 19.90° C. The shape of the drops has been studied, and errors introduced by assuming a spherical shape are shown to be negligible.

scholarly journals Self-Diffusion Coefficients, Aggregation Numbers and the Range of Existence of Spherical Micelles of Oxyethylated Alkylphenols

2021 ◽  
Author(s):  
Victor P. Arkhipov ◽  
Natalia A. Kuzina ◽  
Andrei Filippov
Keyword(s):  
Aqueous Solutions ◽  
Diffusion Coefficients ◽  
The Self ◽  
Self Diffusion ◽  
Aggregation Numbers ◽  
Temperature Ranges ◽  
Spherical Micelles ◽  
Limiting Values

AbstractAggregation numbers were calculated based on measurements of the self-diffusion coefficients, the effective hydrodynamic radii of micelles and aggregates of oxyethylated alkylphenols in aqueous solutions. On the assumption that the radii of spherical micelles are equal to the lengths of fully extended neonol molecules, the limiting values of aggregation numbers corresponding to spherically shaped neonol micelles were calculated. The concentration and temperature ranges under which spherical micelles of neonols are formed were determined.

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