The effect of placing electronegative substituents in the aliphatic portion of alkyl azides appears quite reasonable. By simple inductive means, they would tend to lower the energy of the electrons on NI, and thus increase the energies of both transitions. These are exactly the effects seen in the data of Tables I1 and 111. According to this, the effect should fall off rapidly with the distance of separation of the electronegative group and N1.

No abstract

The objective of this study was to develop an in vitro method to investigate the effect of ultrasound on the in vitro absorption of ibuprofen from a propylene glycol/water vehicle through human epidermis. A diffusion cell was modified so ultrasound could be applied to the vehicle and skin. Since ultrasound can increase the temperature underneath the area of application, control representing temperature effects ran concurrently to the ultrasound experiment. The results demonstrate that ultrasound can increase the penetration of ibuprofen through human skin. This increase in diffusion was greater than for controls where an equivalent increase in temperature was utilized. The results also indicate that evaporation of vehicle components may alter the skin/vehicle partition coefficient, decreasing the effects of ultrasound on the penetration of ibuprofen through the skin.

b A simple and accurate procedure is presented for the determination of pyridoxal. Pyridoxal is condensed with acetone in the presence of a base. Beer's law is obeyed over a concentration range of 10 to 400 pg. The method is suitable for determining pyridoxal in vitamin Be and for the study of nonenzymatic transamination of certain amino acids and keto acids. SIMPLE and accurate method hasA been developed for determining pyridoxal in the presence of pyridoxamine and pyridoxine. This procedure is suitable for studying nonenzymatic transamination of amino acids and is specific for pyridoxal in the presence of other members of the vitamin Be group.Several chemical methods have been reported (1,(3)(4)(5) for determining vitamin Be, but these do not distinguish among pyridoxal, pyridoxamine, and pyridoxine. Metzler and Snell (2) describe a specific colorimetric assay for pyridoxal which is based on the formation of a yellox Schiff base with an excess of ethanolamine. A nonlinear calibration curve over a rather narroTv concentration range was obtained. More recently Wada and Snell (6) have reported a sensitive and specific procedure for determining pyridoxal involving the formation of the phenylhydrazone. c 360 400 4 4 0 4 80 Figure 1 . Absorption spectrum for condensation product formed when pyridoxal is treated with acetone in presence of base Wavelength ( V u )In the proposed procedure pyridoxal is condensed with acetone in the presence of base to give an intense yellow product. The probable equation for the reaction is: CHO HOCHn I OH Base 2 ' 0 ' + CH&OCHB -Junior spectrophotometer. Water was used as a blank. A calibration curve was prepared by plotting absorbance us. concentration.Beer's law was obeyed over this range of concentrations.An alternate procedure was devised which required smaller over-all amounts of pyridoxal hydrochloride. A series of 1-ml. aliquots containing 20 to 400 pg. of pyridoxal hydrochloride was pre-PROCEDURE pared in 10 X 75 mm. cuvettes. To mixed thoroughly, permitted to stand a t room temperature for 15 minutes,The pyridoxal content of samples and then read a t 420 mp in a Coleman for analysis was readily determined concentration was plotted. Table 1. Determination of Pyridoxal Hydrochloride, Free and in Combination with Other Components