ASTM D1123 standard test methods for water in engine coolant concentrate
ASTM D1123 standard test methods for water in engine coolant concentrate by the Karl Fischer reagent method
4. Summary of Test Methods
4.1 These test methods are based essentially on the reduction of iodine by sulfur dioxide in the presence of water. This reaction can be used quantitatively only when pyridine and an alcohol are present to react as follows:
I2 + SO2 + H2O →SO3 + 2HI
4.2 In order to determine water, Karl Fischer reagent is added to a solution of the sample in anhydrous high-purity methanol until all water present has been consumed. This is evidenced by the persistence of the orange-red end point color, or alternatively by an indication on a galvanometer or similar current-indicating device that records the depolarization of a pair of noble metal electrodes. The reagent is standardized by the titration of water.
NOTE 1 - It is believed that these methods give all the information required for determining the water in coolant formulations. Should additional information on water determinations be needed, reference should be made to Test Method E 203.
5. Significance and Use
5.1 The total apparent water in engine coolant concentrate as determined by Karl Fischer titrations consists of the following: (1) water present in the original glycol base; (2) water added (for example, inhibitor solutions); (3) water of hydration of inhibitors (for example, Na 2B4O7•5H2O); (4) water formed in the chemical reaction between borate and ethylene glycol, producing boratediol condensate and water; and (5) quantitative interference by the reaction of the reagent with inhibitors such as tetraborate or sodium hydroxide.
