ASTM D1287 Standard Test Method for pH of Engine Coolants and Antirusts
10. Procedure
10.1 Make the pH determination on (1) the unused concentrated engine coolant or antirust (as received), or (2) any desired dilution, with distilled water, of the concentrated product, or (3) used engine coolant or antirust solution. For dilute solutions, suggested engine coolant concentrations arc 50 and 33 volume %; antirust solution concentration should be in the range of proposed usage. Prepare solutions as follows: Unused engine coolant or antirust solution samples to be tested should be obtained following the applicable portions of the procedure outlined in Practice D1176.
10.1.1 When a small, insoluble liquid layer is present, remove it prior to testing the unused sample or preparing diluted samples for testing. Using a 100-mL mixing cylinder and a pipet or other suitable measuring device, make up a solution of the concentration desired for testing by measuring the necessary amount of antifreeze or antirust solution into the cylinder and adding sufficient distilled water to bring the solution volume to 100 mL.
10.1.2 Thoroughly mix the contents of the cylinder by shaking, and transfer into a 250-mL tall-form spoutless or other suitable beaker.
NOTE 6 - Some pH apparatus is equipped with a sample cup. It is satisfactory to use these cups and the smaller sample required with them, as an alternative to the 100-mL sample and beaker specified.
10.2 Prepare the calomel and glass electrodes as directed in Section 8. Immerse the tip of the electrode in the solution and agitate. Where the instrument has a mechanical stirrer, this may be used. Allow the system to come to equilibrium, and record the pH value. Remove and wash the electrodes with distilled water and immerse them in distilled water until the next determination is made.
NOTE 7 - In the event that the glass electrodes become coated with an oil fitm. as the result of testing two-phase products, it is necessary to remove such film with a suitable solvent such as for inorganic deposits- wash with EDTA, ammonia, or acids; for grease and similar films-wash with acetone or methanol.
NOTE 8 - With silicate-containing engine coolant, it is important to specify that the pH reading be taken either immediately after preparing the dilution or after a specified period of time, such as 30 min. In contrast to an immediate pH, the 30-min value has been shown to be approximately 0.2 units lower and a measurement made alter 24 h can be from 0.3 to 0.5 pH units lower.
