Abstract
In the course of our investigations of the effects of antiseptics and neoarsphenamine on egg albumin and on the colloids of the plasma, it became evident that although the substances tested altered the appearance of egg albumin solutions from the bubble-like picture of lyophillic colloids to the star and comet-like appearance given by the lyophobic colloids, no such intense change was observable when these drugs were added to oxalated rabbit's plasma, or injected intravenously. It did appear, however, that the bubble-like particles of the plasma became definitely brighter in the presence of the drug. In order to obtain a method for objective recording of this fact, we have devised a wedge-photometer, which is applicable to a variety of investigations of colloidal phenomena.
The hollow wedge-shaped chamber of an ordinary wedge-colorimeter is removed from the colorimeter, the opening at the top is sealed with plastein into which a rubber stopper is fitted, and the chamber is filled with a dilute suspension of a colloid. For this purpose we have found a diluted non-water-proof American India Ink very satisfactory. The wedge chamber which we used was from a home-made colorimeter 30 cm. long, 2.5 cm. wide and 2.5 cm. thick at its thickest portion.
In observing the ultramicroseopic particles the photometer wedge was slid across the ocular of the ultramicroscope until the particles being studied just became invisible. The particles were observed at the instant of their maximum brightness. The distances read off on the wedge were then recorded, and the observation was repeated with the second colloid with which the particles first observed were being compared. The illumination (small automatic feed carbon arc), magnification, etc., were kept constant. To exclude the subjective factor, the observations were always checked by 2 observers, whose readings coincided within 0.5 cm.
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