A note on the estimation of carbon dioxide in serum by the Van Slyke method in the presence of ether.

Abstract

When serum contains an amount of ether such as is present in an animal fully anesthetized, an appreciable error is introduced into the analysis of the CO₂ content by the Van Slyke method, using the ordinary technique with either the constant pressure or the constant volume machine. This is due to the extraction of a considerable part of the ether during the initial extraction of the gases and to the reabsorption of most of this ether by physical solution during the absorption of the CO₂ with alkali. By the ordinary technique the apparent CO₂ content may be too high by as much as 10 volumes per cent.

A modification of the technique has been developed which makes it possible to measure the CO₂ in the presence of ether. This consists essentially of reextraction of the alkaline solution after absorption of the CO₂ with alkali. The CO₂ remains held by the alkali but the ether is again extracted in part into the gas phase. An empirical correction must be introduced to correct for a greater solubility of the ether in the acidified solution than in the alkaline solution.