A method for determining the pH of small quantities of fluid

Abstract

The micro-glass electrode used in measuring the pH of blood from the stomachs of mosquitoes was a modification of that described by Caldwell (1954). The electrode was made of capillary tubing, drawn from Corning 015 glass, the outer diameter being 0·5–0·75 mm. and the length about 6 cm. As the electrode was used with a Pye Universal pH meter, and not with the electrometer impedance converter circuit used by Caldwell, it was important that the wall of the capillary tube should be very thin, in order that the resistance of the electrode should not exceed 500 MΩ, the maximum electrode resistance permissible with the Pye Universal pH meter.