March, 19%1 U. S. BUREAU OF CHEMISTRY NOTES. 419

THE PREPARATION OF METHYL-ISOPROPYL-ANTHRAQUINONE.

By Max Phillips.

[ABSTRACT.]

I -methyl-4-isopropyl-anthraquinone has been synthesized from p-cymene and phthalic anhydride. The reaction proceeds in two stages: p-cymene and phthalic anhydride combine to form cymoyl-benzoic acid ; this when condensed in the presence of sulphuric acid yields methyl-isopropyl-anthraquinone. Several derivatives of this anthraquinone have been prepared.

A New Determination of the Constant N of Avogadro, Based on Its Definition. PIERRE LECOMW DU Notiy, Rockefeller Institute for Medical Research. (T-‘hil. Mng., Oct., 1924.)-A few months ago the author made public the results of his study of the changes that take place in the surface tension of solutions of colloidal substances with the lapse of time. He found that a solution of sodium oleate of concentration 1,/750,000 decreased more in its surface tension during the given interval than either stronger or weaker solutions of adjacent concentrations. The minimum thus attained he attributed to the oleate molecules arranging themselves on end upon the bounding surfaces of the liquid and in a single layer. He argued further that, if at this particular concentration the surface was neatly covered by a single layer of oleate molecules, the water molecules would find more difficultv in escaping through this continuous film existing between the a& outside and the water inside that would be the case were the oleate molecules piled up on the surface as in more concen- trated solutions or were they too few to cover the entire surface as in more dilute solutions. He tried this suggested conclusion and actually found the solution of 1/750,000 to evaporate more slowly than the neighboring solutions. He has now gone farther and dis- covered there are for solutions of sodium oleate two additional concentrations for which the surface tension after the passage of two hours is a minimum, so that now three minima are known to show themselves for the concentrations of 1/750,000, 1,/1,220,000 and 1/1,390,000. The author’s understanding of what takes place is this. Conceive the molecule of sodium oleate to possess the form of a brick 8 x 4 x 2 inches. The first minimum corresponds to a film over the surface of contact of the solution with both glass container and air, the molecular bricks forming a pavement 8 inches deep with the dimensions of the bricks in the surface being 4 x 2 inches. In the other cases of minima the length of the brick is parallel to the surface

a Published in J. Aw. Chest. Sm., 46 (Nov., 1924) : 2533.