HONEYWELL’S Lloyd Lazarus has posted a tip on the Metalworking Fluids blog on how metal workers can work out the amount of oil in semi-synthetic or soluble oil and water based fluid.
To divide the oil from metalworking fluid, a process called the acid split test is used. This involves the utilisation of a Cassia flask calibrated from 100 to 110ml.
Two flasks are filled with 100ml samples of the metalworking fluid mix. Three to five millilitres of concentrated sulphuric acid are added to one of the flasks and mixed into the fluid. 5ml of water is then added.
Sulphuric acid destroys the emulsifying agent, freeing the oil in the mix and allowing it to float on top of the water.
24 hours later, the amount of oil in the sample will have formed in the narrow neck of the bottle. Given 100ml of fluid was added in the first place, the amount of oil measured at this stage is an indication of the percentage. For example, 2.2ml of oil will equate to 2.2% oil content.
Sulphuric acid is a hazardous substance, and personal protection equipment should be used if conducting the test. It should also be handled with care and added carefully in small amounts, according to occupational health and safety guidelines.

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