A Quinhydrone-Collodion Electrode of Special Applicability in Experimental Pathology.

Abstract

All the accepted methods of determining the hydrogen ion activity of biological fluids require extensive alteration and manipulation of the fluid itself. If the hydrogen electrode is used, the solution must be saturated with hydrogen; if an oxidation-reduction system is set up, as with quinhydrone, the solution must be saturated with the substance comprising the system. The only exception to this is the glass electrode, which for several reasons is unsuited to routine work.

There appeared to be a real need for an electrode which would be precise in potential values, reasonably rapid in its responses, simple to prepare and, above all, capable of functioning without alteration of the solution being examined. Such an electrode obviously could not be a gas electrode; and of the possible oxidation-reduction systems, the utilization of quinhydrone appeared the most feasible since this system has been well studied.

In principle, the device which we have called the quinhydrone-collodion electrode consists of a very minute collodion sac, the interior of which contains solid quinhydrone. On immersing the sac in the fluid to be examined, the interior, which may have contained water at first, rapidly reaches equilibrium with the exterior with respect to the readily diffusible molecules and ions. Quinone and hydroquinone liberated by the quinhydrone diffuse through the collodion membrane very slowly so that in effect a very small portion of the fluid is isolated and saturated with the quinhydrone. A platinum or gold wire introduced into the interior of the sac will acquire a potential which will be a function of the hydrogen ion activity of the contained fluid.