In 1955, Bowcott and Schulman coined the term microemulsions and, in passing, proposed a cosurfactant titration of interfaces tailored for water-in-oil systems (Bowcott, J. E.; Schulman, J. H. Z. Elektrochem. 1955, 59, 283). This procedure, elegant and inexpensive, is accomplished by dilution with both oil and cosurfactant up to the onset of microemulsion formation. The rationale they proposed for this method should furnish, with high accuracy, the composition of reverse micelles and continuous bulk in the presence of cosurfactant partition. The present paper demonstrates, by means of pulsed gradient spin-echo NMR, that the Schulman's titration quantitatively describes the cosurfactant partition and that the titration path really corresponds to a dilution path for reverse micelles (at constant composition) dispersed in a continuous bulk (at constant composition).