Sodium Cetyl Sulfate Research Articles

Measurement of calcium ion suppression by protection of foam of sodium cetyl sulfate solutions

SummaryRelative protection of various compounds against calcium salts was determined by a pour‐foam test, using sodium cetyl sulfate as a foam‐producing indicator. The sensitivity of the test corresponds to less than 2 p.p.m. of calcium salt.Some of the data are compared with similar tests, using sodium oleate as an indicator, and advantages of the cetyl sulfate test are noted.The test is discussed from the point of view of a competition for calcium ion by the cetyl sulfate anion to precipitate calcium cetyl sulfate and by the compound tested to precipitate a calcium salt or form complex calcium ions.On the basis of the equilibria involved an estimate is made of the approximate solubility of calcium cetyl sulfate in the salt solutions tested.

Metal ion—monolayer interactions. Monolayers of sodium cetyl sulphate and their interaction with polyvalent metal ions

Metal ion—monolayer interactions. Monolayers of sodium cetyl sulphate and their interaction with polyvalent metal ions

Molecular interaction in monolayers. I. Complex formation

With the aid of a compensated Langmuir balance an investigation of the interaction between insoluble monolayers and soluble surface-active compounds has been undertaken by studying monolayer penetration at constant pressure and constant area, and by mixed monolayer compression. The studies have been limited to cases where the interaction is known to be strong. Compression force-area curves of cholesterol spread on solutions of sodium cetyl sulfate and digitonin, and of eicosylamine spread on sodium cetyl sulfate have shown that 1:1 association mixtures of the soluble and insoluble components are stable up to the collapse point of the mixed film. It is suggested that the film which collapses is, in fact, the 1:1 complex. Monolayer penetration experiments at constant surface area on the above systems have yielded results consistent with the earlier hypothesis that under these conditions 1:1 complexes are formed. Experiments at constant surface pressure on single and mixed films have provided further evidence in support of the existence of complexes between cholesterol and digitonin (or saponin); it is shown, however, that such an interpretation cannot be drawn in the experiments involving sodium cetyl sulfate as penetrant. A mechanism has been suggested in outline to explain the characteristic shape of these expansion curves.

Molecular interaction in monolayers. II. Steric effects in the nonpolar portion of the molecules

The interaction between long-chain alcohols and sodium cetyl sulfate has been examined by the monolayer penetration technique. Molecular association is shown to be strongest when the alcohol possesses a straight hydrocarbon chain and can be weakened considerably by altering the configuration of the chain. The concept of a two-dimensional Dalton's Law has been invoked to explain the results obtained with expanded alcohol monolayers at constant pressure.

Adsorption and haemolytic action of diacetyldeoxycholate.

IN an investigation of the relation of the haemolytic activity of sodium cetyl sulphate and sodium lauryl sulphate to their adsorption to red blood cells, we found that haemolysis only starts when a minimum quantity of the detergent is really fixed to the cell walls1,2. On the assumption that such haemolysis does not necessarily involve a unique mechanism, we undertook the study of the relationship between haemolysis and adsorption for a bile acid derivative.

On monolayer penetration

The techniques used for the study of the penetration phenomenon have been discussed in the light of recent work, and a new method of investigation, based on monolayer expansion and using the automatic compensating balance, is described. Two processes have been found to occur, solution and complex formation. For the two systems investigated, cholesterol—sodium cetyl sulfate and cholesterol—saponin, a 1:1 association between monolayer and water—soluble compounds occurs. The cause of the very slow variation in pressure in mixed films has been found to be due to a solution process of the injected molecules into the monolayer. The technique has also been shown to be applicable to the study of tricomplex films. It has also been found that the interaction can be sensitized or partially prevented.

Electrokinetic properties of Cassiterite

Simultaneous ζ-potential and surface conductivity measurements have been made on three samples of cassiterite (SnO2) in water, in solutions of HCl, alkalis, inorganic salts, and the flotation collector reagent sodium cetyl sulphate. It is probable that the intrinsic surface charge of cassiterite in water is negative and that it is due to surface ionization as a very weak acid. Two of the solids possessed a negative surface whilst the positive charge of the third seemed to be due to ionization of a strongly basic impurity. Those samples having a negative charge showed little reaction with sodium cetyl sulphate alone, but appreciable adsorption of cetyl sulphate ion took place in acid solution. On the other hand, the sample with the positive surface reacted with cetyl sulphate ion even in the absence of acid. In all cases adsorption of cetyl sulphate was completely reversible.

Quantitative determination of sodium cetyl sulphate in its solution in water

Quantitative determination of sodium cetyl sulphate in its solution in water

The Adsorption of Sodium Cetyl Sulphate on Cassiterite

The adsorption of sodium cetyl sulphate on pure synthetic cassiterite has been measured under various conditions of concentration and pH and the results related to flotation. It was found that only a small proportion of the surface need be covered with collector ions to make flotation possible. At high concentrations of collector no evidence was found of a double layer of collector ions on the mineral surface, and it is concluded that the cessation of flotation at these concentrations is due to " armouring " of the bubble surfaces. A mechanism for the adsorption of cetyl sulphate ions is proposed, in which these ion3 exchange with hydroxyl ions on the hydrated surface. An attempt is made to describe the ionic equilibria at the cassiterite surface. Samples of natural cassiterite differed from one another and from the synthetic mineral in their ability to be floated under certain conditions : this is attributed to the effect of metallic impurities.

The Sorption of Anionic Detergents by Wool

The rates of sorption of sodium cetyl sulphate by wool at 50d̀c. under varying conditions of salt concentration and pH have been measured. A qualitative explanation of the results is given using the approximation that the concentrations of ions have their stoichiometric relationship (as in equilibrium systems).

Penetration of sodium cetyl sulphate into cetyl alcohol. Effect of salt on the time-penetration curves

Penetration of sodium cetyl sulphate into cetyl alcohol. Effect of salt on the time-penetration curves

The Determination of Critical Concentrations for the Formation of Soap Micelles by the Spectral Behavior of Pinacyanol Chloride

The absorption spectrum of pinacyanol chloride in aqueous solutions of anionic soaps changes sharply to that characteristic of its solutions in organic solvents over a short range of soap concentration. This effect is attributed to the formation of micelles, in whose hydrocarbon-like layers or cores the dye is solubilized. The concentration of soap at which this spectral change occurs is taken as ``the critical concentration for the formation of micelles.'' In water the dye exhibits an absorption band at 5500A which disappears rapidly as the concentration of molecular soap increases. Thus, even 0.00006 molar potassium laurate gives a large effect. At about 0.0126 M the γ-band at about 4800A reaches a high intensity, which falls, with further increase of concentration, very rapidly close to the critical concentration. At 2.3 to 2.4×10−2 for potassium laurate and 6×10−3 for the myristate the α-band (ca. 6150A) and the β-band (ca. 5700A) begin to increase rapidly in intensity and these are considered as the critical concentrations, since these are the prominent bands in the solution of the dye in an oil. Alkali oleate and dilinoleate soaps exhibit an additional band (ω-band) at about 5200A. Some other critical concentrations determined by this method are 3.6–5.2×10−4 molar for sodium cetyl sulfate, 2.5–3.2×10−2 molar for potassium dehydroabietate, 7–12×10−4 molar for potassium oleate, and 2.5×10−4 molar for potassium dilinoleate. The values for the last two soaps are uncertain, since their behavior differs considerably from that displayed by the salts of saturated acids. All measurements were made at 25.8°C with the exception of the sodium cetyl sulfate which was investigated at 35.8°C. An absorption band at approximately 4800A appears in all the soap solutions measured below the critical concentration with the exception of potassium dilinoleate. This band is absent when salts or bases are added to the dye solution. A titrametric method has been developed for the determination of critical concentrations of soaps in the presence of added salts and hydrocarbons.

New Evidence for the Formation of Molecular Complexes in Monolayers by Penetration

THE formation of complexes of definite composition in monolayers as described by Schulman and Stenhagen1, in particular with cetyl alcohol and sodium-cetyl sulphate, has been questioned by Harkins2. Harkins did not succeed in reproducing the discontinuities on the isotherms and has expressed doubt about the existence of the corresponding complexes and the validity of the experimental results in general. In fact, the shape of the isotherms is a function of time, on account of the instability of the monolayer (collapse or solubility) ; it is possible to notice changes of behaviour, of rate of collapse, of stability and of physical state, but without much precision about the molecular areas corresponding to the different regions. I have taken up again this question of the interaction in monolayers between cetyl alcohol and sodium alkyl sulphates using a slightly different technique which removes any doubt about the existence of the 1–1, 1–2 and 1–3 complexes.

The Oil/Water Interface, with and without Monomolecular Film, as a Model of the Living Cell Membrane.1

Summary. 1 An oil/water interface (benzene/salicylic acid solution) has been employed as a model of a cell membrane. 2 The velocity of penetration of salicylic acid from the aqueous into the non-aqueous phase, and the influence of interposed mono-molecular interfacial films (gliadin, sodium cetyl sulphate) on the penetration velocity have been investigated. 3 The penetration constants found were of the order of 106cm2sec-1. An effect of interfacial films on the penetration could not be demonstrated. 4 The reasons for the failure of the interfacial films to affect the penetration are discussed. The influence of the unstirred layers around the phase boundary is found to be negligible. It is concluded that the penetration velocity is principally determined by an “energy barrier” situated in the phase boundary, which must be overcome by the penetrating molecules. 5 The order of magnitude of the penetration constants found in model systems is the same as that observed for living cell membranes. The kinetics of penetration through the latter may therefore be considered as determined by the conditions at the phase boundary as well as by the pore dimensions etc.

The Change with Time of the Surface Tension of Solutions of Sodium Cetyl Sulfate and Sodium Lauryl Sulfate

The Change with Time of the Surface Tension of Solutions of Sodium Cetyl Sulfate and Sodium Lauryl Sulfate

Interaction between adsorbed substances of simple constitution, and insoluble monolayers

Extensive studies of the effect of injecting soluble, capillary active substances underneath insoluble monolayers made in recent years (Hughes 1935; Schulman and Hughes 1935; Schulman and Rideal 1937; Schulman and Stenhagen 1938) have shown that many rather complex, and very easily adsorbed substances can either penetrate an insoluble monolayer, or in some cases displace the monolayer from the surface of the solution. Sodium cetyl sulphate is exceptionally active in penetrating monolayers. Quite recently Bilham (1938) has investigated the reason for the exceptionally low cohesion found by one of us (Adam 1930), with films of long-chain, insoluble amines on acetate buffer solutions of p H about 4; these are gaseous films with very much less lateral cohesion than films of the same amines on other acid solutions of equal or greater acidity. He has shown that the low cohesion is due to the adsorption of acetic acid at the surface, from the buffer solution. He also found that sodium ethyl sulphate has a similar destructive action on the cohesion of amine films. In the work here described, we study the effect of placing insoluble monolayers on the surface of solutions of simple, capillary active substances, principally butyl alcohol, butyric acid, and phenol. Equilibrium between the monolayer and the adsorbed solute appears to be reached very quickly in these cases; generally there is no change in the surface pressure or potential more than about 10 sec. after the area of the film is changed, and a minute always sufficed for the attainment of a final value for the surface pressure or potential, which did not change for an hour or so, provided, of course, that the film was not collapsing.

Effects of Traces of Metallic Ions on Monolayers

IN a recent issue of NATURE, Myers and Harkins1 directed attention to the possibility of considerable errors arising in experiments on monomolecular films where small quantities of ions are introduced from the glass vessel or the metal trough. Experiments which we have carried out recently at University College, London2, show that corresponding errors may arise in the measurement of interfacial tensions as a result of the presence of minute quantities of ions in the distilled water. Thus when using ordinary laboratory distilled water, minima were obtained in the interfacial tension-concentration curves for sodium cetyl sulphate against various oils, the interfacial tension with 0.05 per cent sodium cetyl sulphate being several hundred per cent higher than the minimum which occurred at about 0.015 per cent. Similar results were obtained with sodium salts of other long-chain acids. On using very good conductivity water (specific conductivity 0.l × 106 ohm.1 cm.1 or less) these minima were no longer found. The ordinary distilled water evidently contained small quantities of a cation which strongly depresses the interfacial tension of such systems, its effect being greater in the lower concentrations of long-chain salt.