1. Test preparation.
Measure off 1, 2, 3, 4, 5, 6, 7 g of the concentrate with an accuracy of +/- 0.01 g using a laboratory balance, and pour tap water into each sample up to a total weight of 100 g; stir the solutions thoroughly with glass rods and leave for 40 minutes at room temperature;
Dispense 50 cm3 of the test reference working cutting fluid solution of each concentration into 250 cm3 conical flasks using graduated glassware;
Add 4-5 drops of 1% phenolphthalein alcohol solution to each flask. Then titrate the sample using 0.1 N hydrochloric acid solution until the pink colour in the test solution disappears. Record the amount of hydrochloric acid used for titration.
Using the obtained values, plot the calibration curve on graph paper by plotting the amount of hydrochloric acid (used for titration) along the Y-axis and the concentration of the cutting fluid solution along the X-axis.
It is recommended to centrifuge the sample of the working cutting fluid solution collected from the cooling system of the machine in order to separate “foreign” oils and solids;
Dip a measuring pipette into the middle part of the sample (preventing ingress of the top layer that usually contains “foreign” oils);
Add 4-5 drops of 1% phenolphthalein alcohol indicator to the sample. Then titrate the sample using 0.1 N hydrochloric acid solution until the pink colour in the test solution disappears. Record the amount of hydrochloric acid used for titration.
Determine the concentration of the working solution based on the amount of the acid used for titration using the calibration curve.
