[gudenlau]

I did read in a book that they used Karl fischer method(http://en.wikipedia.org/wiki/Karl_Fischer_titration) to measure the water content in lube oils. We want to know how much of the water remains in the lube oil after a run in the oil purifier. We expect the content to be from 0,1-0.3%. We use RH% sensors on the outlet on the oil purifier that says there is 0%(no decimals). We dont belive that the water content is actually 0%.

Can we use the Karl Fischer method to measure the water content? The wiki site states that "The major disadvantage is that the water has to be accessible and easily brought into methanol solution. Many common substances, especially foods such as chocolate, release water slowly and with difficulty, and require additional efforts to reliably bring the total water content into contact with the Karl Fischer reagents."

[Stepan]

There is a simple device for water in oil test. It is a pressure gauge connected to the vessel with oil, where you add CaH2. Last one reacts with H2O, H2 is produced. Pressure in the vessel increases proportionally to water content

[curiouscat]

There is a simple device for water in oil test. It is a pressure gauge connected to the vessel with oil, where you add CaH2. Last one reacts with H2O, H2 is produced. Pressure in the vessel increases proportionally to water content

Interesting! Though at 1% water levels the amount of H2 produced must be fairly small. What's the solubility of H2 in typical oils?

Could one use Calcium Carbide and base it on acetylene gas pressure? I wonder..

[Arkcon]

You can use the Karl Fisher method, but it isn't as easy as Wikipedia describes.  The hardest part is definitely not purchasing anhydrous methanol.  You have to calibrate the system carefully, and execute the protocol very carefully.  With practice, you can get good at the procedure, and when the rig is set up properly, the system can be flawless.  The darn problem is that, if you're a human, working on the surface of the planet Earth, there are always traces of moisture.  And if the sample gets contaminated, the auto-dispensing titrator just goes haywire.  And you have to let it finish before you flush out the chamber and start over.

[Corribus]

Have you considered thermogravimetric analysis (TGA)?  You can use this to determine water content in a lot of different substances.

[Stepan]

There is a simple device for water in oil test. It is a pressure gauge connected to the vessel with oil, where you add CaH2. Last one reacts with H2O, H2 is produced. Pressure in the vessel increases proportionally to water content

Interesting! Though at 1% water levels the amount of H2 produced must be fairly small. What's the solubility of H2 in typical oils?

Could one use Calcium Carbide and base it on acetylene gas pressure? I wonder..

Approximately 250 mL H2 on 50 ml oil sample. Solubility in oil is almost zero.
Calcium carbide is hard to use, as it reacts very slowly due to very limited surface area. We tried it for different application - to measure moisture content if gas stream.

[Stepan]

Have you considered thermogravimetric analysis (TGA)?  You can use this to determine water content in a lot of different substances.

I think TGA will be hard to use as the oil will foam when water boils. You can use oven drying at 105C, but you do not know how much weight loss is attributed to volatile organic.