scholarly journals The structure of surface films. Part XVIII. ─The effect of alkalinity in the underlying solution on films of fatty acids

1933 ◽  
Vol 142 (847) ◽  
pp. 401-415 ◽  
Keyword(s):  
Fatty Acids ◽  
Acid Solution ◽  
Aqueous Solutions ◽  
Complete Solution ◽  
Alkaline Solutions ◽  
Carboxyl Group ◽  
Surface Films ◽  
Electrolytic Dissociation ◽  
End Groups ◽  
Monomolecular Films

Historical . It has been known for some time that extensive changes occur in monomolecular films of fatty acids on aqueous solutions, as the alkalinity or acidity is varied. These changes are of at least tow kinds; changes in the packing of the molecules in the coherent types of film, and changes in the lateral adhesion between molecules have already been described. Thus Adam found changes in the packing of the molecules in the condensed films on changing from neutral to acid solution; and also a change from condensed to gaseous or vapour expanded films, on changing from natural to strongly alkaline solutions. The second of those effects was considered to be due to a decrease in the lateral adhesion between the molecules, caused by the development of similar electric charges on the end groups, through electrolytic dissociation of the carboxyl group on alkaline solutions. On alkaline solutions, it has previously been noted that the films contract spontaneously; Adam called this "solution," but did not examine it in detail; Lyons and Rideal believed it to be not a complete solution, but the formation of a bimolecular layer two molecules thick; Zocher and Stiebel, by ultramicroscopic examintion, concluded that this disappearance of the film was due to a partial collapse into thick, localized aggregates, not into a uniform bimolecular film.

scholarly journals The structure of surface films. Part XIX.—Influence of alkaline solutions on films with various end groups

1933 ◽  
Vol 142 (847) ◽  
pp. 416-422 ◽  
Keyword(s):  
Caustic Soda ◽  
Surface Pressure ◽  
Soluble Group ◽  
Alkaline Solutions ◽  
Surface Films ◽  
Polar Group ◽  
Pressure Measurements ◽  
End Groups ◽  
Pressure Area

In this paper, the effect of alkalinity of the underlying solution on substances with end groups other than carboxyl is studied. Surface pressure measurements only were made. Fig. 1, curves I to III, show the pressure-area relations found with three members of the series on twice normal caustic soda. The acid with n = 32 is condensed at 20°, tending to an area at no compression of about 30 sq. A.; this figure is not very accurate, owing to collapse of the films; the area is nearly the same as with the films of monobasic acids on this solution. The condensed films of these dibasic substances, with a polar group at each end of chain, were shown in Part IX to be oriented upright with one soluble group only in the water. On 2N soda, the acids with n = 24 and 20 are both gaseous at the lowest temperature attainable (3°), the acid ( n = 20) being the naturally the more perfectly gaseous film.

scholarly journals The structure of surface films. Part XVII.—γ hydroxy-stearic acid and its lactone

1933 ◽  
Vol 140 (840) ◽  
pp. 223-226 ◽  
Keyword(s):  
Stearic Acid ◽  
Aqueous Solutions ◽  
Surface Pressure ◽  
Surface Films ◽  
Hydroxy Stearic Acid ◽  
Monomolecular Films ◽  
Made In

This paper describes observations, mostly made in 1924 and not hitherto published in detail,* on the surface pressure of γ hydroxy-stearic acid (I) and its lactone (II) spread as monomolecular films on aqueous solutions. CH3 3 CH3 3 (CH 2 ) 13 (CH 2 ) 13 CHOH CH CH 2 CH 2 CH 2 O COOH CH 2 – CO I II Most of the measurements were made with the modification of Langmuir’s apparatus described in Parts I and II of this series of papers,† in which jets of air prevent the film passing the ends of the float. A few confirmatory observations have been made since, with the apparatus of Adam and Jessop, in which thin metallic ribbons block these gaps. The acid and lactone were kindly given me by Dr. P. W. Clutterbuck, of Manchester University.

scholarly journals The structure of surface films. Part XVI.—Surface potential measurements on fatty acids on dilute hydrochloric acid

1932 ◽  
Vol 138 (835) ◽  
pp. 411-430 ◽  
Keyword(s):  
Fatty Acids ◽  
Dipole Moment ◽  
Dilute Hydrochloric Acid ◽  
Vertical Component ◽  
Water Molecules ◽  
Surface Films ◽  
Pressure Measurements ◽  
Contact Potential ◽  
Surface Potential Measurements ◽  
Air Liquid Interface

Guyot, Frumkin, and Schulman and Rideal have shown that it is possible, by means of an air electrode covered with a small amount of a radioactive deposit, which ionises the air in its neighbourhood, to measure changes in the contact potential at an air-liquid interface caused by spreading a film over the surface. It is now clear that this change in contact potential is caused by the dipoles of the film molecules, the magnitude of the change in potential depending on the vertical component of the dipole moment of the molecules in the film, and on the extent to which the water molecules and the ions in the solution are re-arranged near the surface under the influence of these dipoles. In combination with surface pressure measurements, which have already given a great deal of information as to the orientation of the molecules in the surface, and their shapes, sizes, and adhesive fields of force, this method, which indicates the orientation of the dipoles of the film molecules to the surface, is a valuable addition to our methods of investigating the structure of surface films.

Fatty Acids: Crystals, Monomolecular Films, and Soaps

Lipids ◽  
1986 ◽  
pp. 49-68 ◽  
Author(s):  
James F. Mead ◽  
Roslyn B. Alfin-Slater ◽  
David R. Howton ◽  
George Popják
Keyword(s):  
Fatty Acids ◽  
Monomolecular Films
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