Determination of micellar weights for di-alkyl sodium sulfosuccinates in anhydrous and hydrous hydrocarbon solutions

✍ Scribed by Sylvan G. Frank; George Zografi

• Publisher: John Wiley and Sons
• Year: 1969
• Tongue: English
• Weight: 747 KB
• Volume: 58
• Category: Article
• ISSN: 0022-3549
• DOI: 10.1002/jps.2600580820

✦ Synopsis

Sorensen Buffer-Table VI lists the literature and calculated values along with the experimentally determined values of pH for the 10 official phosphate buffer mixtures. It can be seen that the pH values reported by Sorensen (10) and cited by Goyan and Hind (4) in their formulation of isotonic phosphate buffer mixtures which have been transcribed into the USP (8) and NF (9) agree quite well with the experimental values obtained in this study at 25". However, it should be pointed out that the pH values found in the USP (8) and NF (9) are somewhat ambiguous since they do not represent isotonic buffers' pH values as they might lead one to suspect; but instead represent the buffer mixtures' pH before the addition of the appropriate amounts of sodium chloride needed to render the solution isotonic. A rigorous approach involving all phosphate equilibria, mass balance, and charge balance was employed in calculating the pH. Because of the complexity of the relationship that results from such a rigorous approach, a computer (IBM-1130) was used to perform the required Newton-Raphson iteration. It can also be noted in Table VI that tonicity values calculated from freezing point depression data of the buffer mixtures are somewhat lower than those determined experimentally with the osmometer at 37". This seems to indicate that at higher temperatures the ability of phosphate species to associate is slightly diminished. This was found to be true when the phosphate salts' E values were reviewed. Table I1 illustrates that the E values of both phosphate salts are 5 to 10% higher at 37" than at 0". The pH values of the buffer mixtures at 37" are also included in Table VI.

The compilation of the data obtained in the re-evaluation of the official isotonic phosphate buffer found in Table VII demonstrates that the 10 buffer mixtures that were calculated to be isotonic at 0" are slightly hypertonic at 37". The resulting solutions were hypertonic due to the low tonicity values assigned to the buffer mixtures which dictated the quantities of sodium chloride that would be necessary to render the buffers isotonic. The pH values for these buffer mixtures at 25 and 37" are listed in Table VII. The USP (8) and N F (9) do not list such values; however, it was thought more important to know the pH of the resulting mixtures than the pH of the buffer mixture itself.