Quantitative treatment of indicator equilibria in micellar solutions of sodium decyl phosphate and sodium lauryl sulfate

Laurence Romsted, Dino Zanette

Research output: Contribution to journalArticle

65 Citations (Scopus)

Abstract

The pseudophase ion-exchange (PIE) model provides both a qualitative and quantitative interpretation of micellar effects on reaction rates and equilibria for a number of reactions between organic molecules and ions in aqueous solution in the presence and absence of buffer. Our results show that this model is also applicable to micellar solutions of sodium decyl phosphate monoanion, NaDP. We measured the ratio of the acid and base forms of the indicator, pyridine-2-azo-p-dimethylaniline (PADA), in the pH range of 4-6, succinate buffer, at a variety of surfactant and counterion concentrations. Measurements were carried out at 50°C to ensure that NaDP remained in solution at the lower end of the pH range. Parallel experiments were run in sodium lauryl sulfate, NaLS, to check for special effects of the head groups of micellized NaDP in the indicator equilibria. None were found. NaDP micelles behave "normally", and the assumptions of the model are well-obeyed provided (a) measured values of the pH are used instead of assuming that the buffer maintains the pH of the aqueous phase constant at all salt concentrations and (b) the concentrations of sodium ions in the aqueous phase are converted to activities by using the mean ion activity coefficient of NaCl. Limitations of the approach and sources of error are discussed.

Original languageEnglish (US)
Pages (from-to)4690-4698
Number of pages9
JournalJournal of physical chemistry
Volume92
Issue number16
DOIs
StatePublished - Jan 1 1988

Fingerprint

Sodium dodecyl sulfate
sodium sulfates
Sodium Dodecyl Sulfate
phosphates
Buffers
Phosphates
Sodium
sodium
Ions
buffers
Special effects
ions
Activity coefficients
Micelles
Succinic Acid
Surface-Active Agents
Pyridine
Reaction rates
Ion exchange
Surface active agents

All Science Journal Classification (ASJC) codes

  • Engineering(all)
  • Physical and Theoretical Chemistry

Cite this

@article{f9af106172cb46a38f4844fa31bd445e,
title = "Quantitative treatment of indicator equilibria in micellar solutions of sodium decyl phosphate and sodium lauryl sulfate",
abstract = "The pseudophase ion-exchange (PIE) model provides both a qualitative and quantitative interpretation of micellar effects on reaction rates and equilibria for a number of reactions between organic molecules and ions in aqueous solution in the presence and absence of buffer. Our results show that this model is also applicable to micellar solutions of sodium decyl phosphate monoanion, NaDP. We measured the ratio of the acid and base forms of the indicator, pyridine-2-azo-p-dimethylaniline (PADA), in the pH range of 4-6, succinate buffer, at a variety of surfactant and counterion concentrations. Measurements were carried out at 50°C to ensure that NaDP remained in solution at the lower end of the pH range. Parallel experiments were run in sodium lauryl sulfate, NaLS, to check for special effects of the head groups of micellized NaDP in the indicator equilibria. None were found. NaDP micelles behave {"}normally{"}, and the assumptions of the model are well-obeyed provided (a) measured values of the pH are used instead of assuming that the buffer maintains the pH of the aqueous phase constant at all salt concentrations and (b) the concentrations of sodium ions in the aqueous phase are converted to activities by using the mean ion activity coefficient of NaCl. Limitations of the approach and sources of error are discussed.",
author = "Laurence Romsted and Dino Zanette",
year = "1988",
month = "1",
day = "1",
doi = "10.1021/j100327a027",
language = "English (US)",
volume = "92",
pages = "4690--4698",
journal = "Journal of Physical Chemistry",
issn = "0022-3654",
publisher = "American Chemical Society",
number = "16",

}

Quantitative treatment of indicator equilibria in micellar solutions of sodium decyl phosphate and sodium lauryl sulfate. / Romsted, Laurence; Zanette, Dino.

In: Journal of physical chemistry, Vol. 92, No. 16, 01.01.1988, p. 4690-4698.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Quantitative treatment of indicator equilibria in micellar solutions of sodium decyl phosphate and sodium lauryl sulfate

AU - Romsted, Laurence

AU - Zanette, Dino

PY - 1988/1/1

Y1 - 1988/1/1

N2 - The pseudophase ion-exchange (PIE) model provides both a qualitative and quantitative interpretation of micellar effects on reaction rates and equilibria for a number of reactions between organic molecules and ions in aqueous solution in the presence and absence of buffer. Our results show that this model is also applicable to micellar solutions of sodium decyl phosphate monoanion, NaDP. We measured the ratio of the acid and base forms of the indicator, pyridine-2-azo-p-dimethylaniline (PADA), in the pH range of 4-6, succinate buffer, at a variety of surfactant and counterion concentrations. Measurements were carried out at 50°C to ensure that NaDP remained in solution at the lower end of the pH range. Parallel experiments were run in sodium lauryl sulfate, NaLS, to check for special effects of the head groups of micellized NaDP in the indicator equilibria. None were found. NaDP micelles behave "normally", and the assumptions of the model are well-obeyed provided (a) measured values of the pH are used instead of assuming that the buffer maintains the pH of the aqueous phase constant at all salt concentrations and (b) the concentrations of sodium ions in the aqueous phase are converted to activities by using the mean ion activity coefficient of NaCl. Limitations of the approach and sources of error are discussed.

AB - The pseudophase ion-exchange (PIE) model provides both a qualitative and quantitative interpretation of micellar effects on reaction rates and equilibria for a number of reactions between organic molecules and ions in aqueous solution in the presence and absence of buffer. Our results show that this model is also applicable to micellar solutions of sodium decyl phosphate monoanion, NaDP. We measured the ratio of the acid and base forms of the indicator, pyridine-2-azo-p-dimethylaniline (PADA), in the pH range of 4-6, succinate buffer, at a variety of surfactant and counterion concentrations. Measurements were carried out at 50°C to ensure that NaDP remained in solution at the lower end of the pH range. Parallel experiments were run in sodium lauryl sulfate, NaLS, to check for special effects of the head groups of micellized NaDP in the indicator equilibria. None were found. NaDP micelles behave "normally", and the assumptions of the model are well-obeyed provided (a) measured values of the pH are used instead of assuming that the buffer maintains the pH of the aqueous phase constant at all salt concentrations and (b) the concentrations of sodium ions in the aqueous phase are converted to activities by using the mean ion activity coefficient of NaCl. Limitations of the approach and sources of error are discussed.

UR - http://www.scopus.com/inward/record.url?scp=0001224895&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0001224895&partnerID=8YFLogxK

U2 - 10.1021/j100327a027

DO - 10.1021/j100327a027

M3 - Article

VL - 92

SP - 4690

EP - 4698

JO - Journal of Physical Chemistry

JF - Journal of Physical Chemistry

SN - 0022-3654

IS - 16

ER -