The validity of prediction of shelf stability from ultracentrifugal parameters determined on newly prepared Nujol-in-water emulsions stabilized with sodium dodecylsulfate (0.2 to 0.4%), cetylpyridiniumchloride (0.1 to 0.2%), Triton X-100 (0.08 to 0.4%), or Tween 20 (0.08 to 0.4%) was tested by allowing samples to age for periods up to 3 yr. They were then reexamined visually, and an empirical rating scheme devised for describing their stability semiquantitatively. In some cases it was also possible to redetermine the ultracentrifugal parameters on the aged emulsions. None of the ultracentrifugal parameters of the fresh emulsions predicted the order of actual shelf stability correctly in all cases. Possible reasons for the discrepancies are discussed.

The rate of loss of oil from 50% Nujol-50% water emulsions stabilized with varying concentrations of Tween 20 or Triton X-100, and from 50% olive oil-50% water emulsions stabilized with sodium dodecyl sulfate (SDS), was determined by ultracentrifugation at 39,460 rpm. In all cases the ultracentrifugal stability increased with increasing initial concentration of emulsifier, although, unlike the behavior of Nujol-water-SDS emulsions, the rate of separation of oil decreased with time. The quantity of olive oil separated after a given time of centrifugation decreased linearly with increasing concentration of SDS, reaching zero at a concentration of SDS somewhat below the critical micelle concentration, and at adsorption of SDS corresponding to only about half the saturation capacity. The ultracentrifugal stability of Nujol emulsions with Tween 20 or Triton X-100 continued to increase slowly with increasing concentration of emulsifier, even at concentrations far greater than the critical micelle concentration.

The rate of separation of oil from Nujol-water emulsions stabilized with sodium dodecylsulfate (SDS), cetyl pyridinium chloride (CPyCl), Tween 20 or Triton X-100 was determined over the temperature range from 5 to 30°C in an ultracentrifuge at 39,460 rpm. The emulsions were all found to be less stable at the higher temperatures, but the change in stability with temperature was such as to suggest that it is not caused primarily by changes of the viscosity with temperature. The results with SDS could be fitted to a zero-order rate expression, leading to a calculated activation energy of 9.0 kcal, but the rate of loss of oil by the other emulsions conformed to no simple rate law.

The optical density of carbon black suspensions in heptane, toluene, and solutions of polystyrene in toluene and in cyclohexane, decreases with time and ultimately reaches a steady-state value. This is interpreted in terms of the simultaneous occurrence of flocculation and deflocculation following, respectively, second- and first-order kinetic rate laws. A method is developed for obtaining an absolute value of β, the rate constant for deflocculation, from the time dependence of the optical density, assuming that optical density is proportional to floc concentration.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Effect of Varying Centrifugal Field and Interfacial Area on the Ultracentrifugal Stability of Emulsions1,2Robert D. Vold and Robert C. GrootCite this: J. Phys. Chem. 1964, 68, 12, 3477–3484Publication Date (Print):December 1, 1964Publication History Published online1 May 2002Published inissue 1 December 1964https://pubs.acs.org/doi/10.1021/j100794a006https://doi.org/10.1021/j100794a006research-articleACS PublicationsRequest reuse permissionsArticle Views61Altmetric-Citations19LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts

The rate of separation of oil from 50 volume per cent Nujol-50 volume per cent water emulsions stabilized with either 0.2% or 0.4% sodium dodecyl sulfate (SDS) on the basis of the aqueous phase was determined on ultracentrifugation at 113,200 g over a range of concentrations of sodium chloride from zero to 0.1 M. The oil-water interfacial area of these emulsions and the effect of added salt on the adsorption of SDS at the interface were also determined.

ADVERTISEMENT RETURN TO ISSUEPREVReportNEXTSummer conference: Fundamental aspects of colloid and macromolecular chemistryRobert D. Vold Cite this: J. Chem. Educ. 1962, 39, 4, 193Publication Date (Print):April 1, 1962Publication History Received3 August 2009Published online1 April 1962Published inissue 1 April 1962https://doi.org/10.1021/ed039p193RIGHTS & PERMISSIONSArticle Views26Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts

Formation of precipitates or soluble complexes between solutions of zinc chloride and surfactants was investigated by means of pH and conductivity titrations. Precipitates were characterized by chemical analysis and X-ray diffraction.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAN ULTRACENTRIFUGAL METHOD FOR THE QUANTITATIVE DETERMINATION OF EMULSION STABILITY1Robert D. Vold and Robert C. GrootCite this: J. Phys. Chem. 1962, 66, 10, 1969–1975Publication Date (Print):October 1, 1962Publication History Published online1 May 2002Published inissue 1 October 1962https://pubs.acs.org/doi/10.1021/j100816a037https://doi.org/10.1021/j100816a037research-articleACS PublicationsRequest reuse permissionsArticle Views201Altmetric-Citations43LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts

Observations at a series of temperatures of the changes in viscosities and depolarization factors of 1% and 18% solutions of calcium stearate in cetane to which varying amounts of water have been added can be interpreted in terms of the existence of anisometric micelles. In general, changes in the size of the micelles inferred from values ofρh agree with those deduced from the viscosity data. The correlation between anisometry of micelles from rheological and optical observations is much poorer in the case ofρν, presumably because of the difficulty in differentiating the contribution of anisometry and anisotropy toρν.

ADVERTISEMENT RETURN TO ISSUEPREVBook and Media Revie...Book and Media ReviewNEXTThe Chemistry and Physics of Clays and Other Ceramic Materials (Searle, Alfred B.; Grimshaw, Rex W.)Robert D. Vold Cite this: J. Chem. Educ. 1960, 37, 2, 108Publication Date (Print):February 1, 1960Publication History Received3 August 2009Published online1 February 1960Published inissue 1 February 1960https://doi.org/10.1021/ed037p108.3RIGHTS & PERMISSIONSArticle Views781Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts

Preparations of sodium humate made by different extractive procedures all showed a similar dependence of reduced viscosity on concentration and on added salt despite the fact that lignins were present in some preparations and absent in others. The results obtained are characteristic of the behavior of flexible polyelectrolytes, and suggest that the sodium humate molecule or aggregate must have many single bonds in its structure so as to permit the indicated configurational changes. In the case of the purest sodium humate studied the apparent degree of dissociation is only about 50%.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTechnical education and development in an Indian environmentRobert D. Vold Cite this: J. Chem. Educ. 1958, 35, 10, 522Publication Date (Print):October 1, 1958Publication History Received3 August 2009Published online1 October 1958Published inissue 1 October 1958https://pubs.acs.org/doi/10.1021/ed035p522https://doi.org/10.1021/ed035p522research-articleACS PublicationsRequest reuse permissionsArticle Views36Altmetric-Citations1LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Origin of the Maximum in the Adsorption Isotherms of Association ColloidsRobert D. Vold and N. H. SivaramakrishnanCite this: J. Phys. Chem. 1958, 62, 8, 984–989Publication Date (Print):August 1, 1958Publication History Published online1 May 2002Published inissue 1 August 1958https://pubs.acs.org/doi/10.1021/j150566a025https://doi.org/10.1021/j150566a025research-articleACS PublicationsRequest reuse permissionsArticle Views107Altmetric-Citations55LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts