NEW MEETING FOR DETERMINING THE RATE OF DIFFUSION (MOBILITY) OF SURFACE ACTIVE MOLECULES ON A SOLID--GAS BOUNDARY SURFACE

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP82-00039R000100110054-0
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 4
• Document Creation Date: December 22, 2016
• Document Release Date: June 8, 2012
• Sequence Number: 54
• Publication Date: April 12, 1951
• Content Type: REPORT

Declassified in Part - Sanitized Copy Approved for Release 2012/06/08 : CIA-RDP82-00039R000100110054-0
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Titles NEW METHOD FOR DETEIUW INO T RATE OF D~FPUSION MOBILITY)
OF SURFACE ACTIVE MOLECULES ON A SOLID -- (SAS BOUNDARY SURFACE
USSR B. F. Pokhil
Souroet Zhurnal Fizioheekoy Xhind.1, Vol XIII, No 1, 1939, pp 146
(O1FtDE1M.
Declassified in Part - Sanitized Copy Approved for Release 2012/06/08 : CIA-RDP82-00039R000100110054-0
 Declassified in Part - Sanitized Copy Approved for Release 2012/06/08 : CIA-RDP82-00039R000100110054-0
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CONFIDENTIAL
NEW TNOD Fort DETE PIING THE RATE OF DIF)iJ5oNthoBILrn )_OE
BUIU'AOE ACTWE MOLECULES ON A 5O14 ?~ GAS 8SURFACE
E. F. Pokhil
Lab of Surface Phenomena,
Inst for Phye and Chem Inveetigatione,
Leningrad
we have developed a new method for determining the rate of diffueion of
eurfaoe-active eubetanoea on the boundary eurfaoe between a solid eubetanoe
and a gas. Thie method yielde reproducible resulte. The principle of the
method ie deeoribed below.
If a platinum plate which had been previouely heated on a flame in or-
der to olea~ it ie brought into contact at one end with a eurfaoe of water
pourod into an LSD]' Adam balance while a surface-active oompound (for in-
~
etance, oleio acid) ie introduced onto the other end of the plate (the one
which ie eurrounded by air), the eurfaoe-active compound begins to evaporate
into the two-dimensional apace formed by tho solid -? gas boundary. The
rate of thie evaporation depends prinoipally on the nature of the underlying
eurfaoe anal the temperature of the surrounding medium. When the moleoulee
of the eurfaoe-active compound reach the oppoeite end of the plate (the one
which is in contact with water), they naturally begin to spread rapidly over
the water eurfaoe, indicating this fact by the two-dimensional pressure ore-
ated by them. This preeeure ie regietered c1iraotl3' by the Adam balance. Be-
fore each experiment the Adam balance ie brought into an operating condition;
then one end of the metal plate is brought into contact with the water eurfaoe,
the surface-active eubetance is introduced at the other end, and the number
of moleoulee transferred from the plate onto the water eurfaoe is determined
ac a funotion of time by means of the Adam balance. In oaeee when the dif-
fueion of a cubetance which develops a considerable pressure in the gas phase
of the film formed by it is studied, this pressure can be used directly for
determining the concentration of the e~betanoe in the film, i.e., the number
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CONFIDENTIAL
Declassified in Part - Sanitized Copy Approved for Release 2012/06/08 : CIA-RDP82-00039R000100110054-0
 Declassified in Part - Sanitized Copy Approved for Release 2012/06/08 : CIA-RDP82-00039R000100110054-0
(ONFI DEN hAL
of moleouleo tranoferrod From the plate to the eurfaoe of the water within
any given period of time. In order to do this, it ie only neoeesary to plot
the J~ our, wherelT'is the two-dimensional pressure exerted by the
film, and the area per 1 mol 5er I olecule in angetroma square37, or
use published data.
by relating two-dimaneional preasureo found in the investigation of the
diffusion rate to preoeuree from /1'. curves, we ow determine directly the
values in which we are intereeted. The bent reoulte, ac far as rc, duoi-
bility ie conoernod, are obtained at tow two-dinsenaional preeeuree oorree-
ponding to a gaeeoue etate or one near to it.
In the uaee of eubetanooe the gaeeouc file phase of which exhibits
very low two-dimen$ional preesuree (preeeuree which praotioally cannot be
determined), it ie neoeeeary to remove the net-a1 plate after keeping it for
some definite tiae in contact with the water eurfaoe, and then oomprees the
film until thn latter begins to break. If the total area ocoupiod by all
moleoulee of the film at the time when the film begins to break up is lmown,
and the limiting area corresponding to one molecule of the substance in
quostion is also known (for instance, this area oorreepondo to 20,5 angetrome
square in the case of myrietio acid), the number of moleculee tzraneferred
from the eurfaoe of the plate to thn eurfaoe of the water during the time
when the plate was in contact with the water can be calculated. The point at
which the film begins to break up is clearly noticeable, so that any error
which may occur due to thn determination of this point is ineignifioant.
Thie permitted us to utilize the phenomenon of film breakage not only in the
investigation described above, but also for tho study of adsorption of surf-
ace-active compounds by solid adsorbente. The latter investigation has not
yet been published.
In studying the rate of diffusion in the boundary solid-gas of mole-
oulee of crystalline (solid) surfaoe-aotive ubstanoee (for instance, myristio
acid) it is neoessary to have a temperature of the surrounding medium which
is higher than the oritical temperature of the substance; otherwise the
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CONFIDENTIAL
Declassified in Part - Sanitized Copy Approved for Release 2012/06/08 : CIA-RDP82-00039R000100110054-0
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Declassified in Part - Sanitized Copy Approved for Release 2012/06/08 : CIA-RDP82-00039R000100110054-0
(014F1 DENTIAL
e betanoe o nnot evapor Ito into the two-diiiienoiunal $paoe. A eP1a11 oryatal
of tho aubetanoe under invoatiation io fund to the end of the metal plate
removed from the water. Subsequently the experimont is aarried out as des?
oribod above. The reeulte of an investigation of trio typo will be published
by uQ in the future.
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CONFIDENTIAL
Declassified in Part - Sanitized Copy Approved for Release 2012/06/08 : CIA-RDP82-00039R000100110054-0