Improvements relating to reference electrodes for ph meters, and electrolyte solutions therefor

摘要

900,248. Electrolytic testing apparatus. NATIONAL RESEARCH COUNCIL. June 10, 1960 [June 15, 1959], No. 20410/60. Class 37. A reference electrode for pH determination is made suitable for operation at very low temperatures by using it with a salt bridge containing an aqueous solution of potassium chloride to which is added a sufficient quantity of a specified stable polyalcohol Fig. 1 shows a calomel reference electrode comprising aqueous paste 26 of mercurous chloride and potassium chloride in contact with mercury 24 to which is connected a lead 11. An aperture 27 provides ionic conduction to a saturated potassium chloride solution contained in a tube 10 having a capillary opening 12 connecting with a further saturated potassium chloride solution 13 containing 20-100% of glycerol, ethylene glycol, diethylene glycol or diethylene glycol monoethyl ether. The organic additive is stated to allow operation over a temperature range from - 40‹ C. to over 100‹ C. The organic substance may additionally be added to the electrolyte in tube 10. The reference electrode is connected via a small bore tube 19 having a flow-restricting aperture 21 and a stop cock 20 to the test sample 40. The apparatus is suitable for the determination of pH concentration in frozen milk and other foods as well as soils and plants in frozen state. The invention may be applied to a silver/silver chloride half-cell.