Sodium sulphanilate

Additional physico-chemical information

Administrative data

Endpoint:

other: Osmotic and activity coefficient

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

November 10, 1981

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: Experimental result from a Bibliographic source.

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1981

Report date:

1981

Materials and methods

Test guideline

Qualifier:

no guideline followed

Deviations:

not applicable

GLP compliance:

not specified

Results and discussion

Results:

Osmotic coefficients at 298.15K: 0.928 (0.1m), 0.919 (0.2m), 0.912 (0.3m), 0.906 (0.4m), 0.904 (0.5m).

Activity Coefficients at 298,15K: 0.773 (0.1m), 0.725 (0.2m), 0.694 (0.3m), 0.673 (0.4m), 0.658 (0.5m).

Applicant's summary and conclusion

Executive summary:

Osmotic and acttvity coefficients are reported for solutions of the sodium sulfanilic acid and for the parent acid.

The sulfanilic acids were purchased as the certified grade with lot analysis from Fisher Scientific Co. The sulfamic acid was stored under vacuum over P₂0₅, and the molecular weight by titration agreed with the theoretical weight within the uncertainty of the titration. The dried sample was used without further purification. The sulfanilic acid was the monohydrate, but it was too insoluble for isopiestic studies in any case. Samples of both parent acids were carefully neutralized with NaOH or KOH, and the salts were recrystallized

from alcohol-water mixtures.

The osmotic and stoichiometric activity coefficients at rounded concentrations were reported by the extrapolation of the molality ratio m(NaCl)/m(sutfamic acid) to infinite dilution. Data at constant water activities for HIO₃ and sulfamic acid solutions were, therefore, used to aid in the extrapolation.

Results obtained for sodium 4-aminobenzenesulfonate were as follows:

Osmotic coefficients at 298.15K: 0.928 (0.1m), 0.919 (0.2m), 0.912 (0.3m), 0.906 (0.4m), 0.904 (0.5m).

Activity Coefficients at 298,15K: 0.773 (0.1m), 0.725 (0.2m), 0.694 (0.3m), 0.673 (0.4m), 0.658 (0.5m).

Results indicated the order of osmotic coefficients for a strong acid and its salts at any concentration is H⁺ > Li⁺ > Na⁺ > K⁺, an order due primarily to the differing degrees of hydration of the cations. Incomplete ionization causes the coefficient of an acid to be smaller than that of its salts. The ratio of the coefficients of an acid and its sodium salt at any concentration gives a rough idea of the degree of ionization since the solvation effect of the anion is largely compensated, especially in the case of fairly large anions.