[poorstudent83]

Hi.

I'm wondering what's the safe "highest temperature" for a paraffin oil bath.

I need to heat at 230 deg for 6 - 7 hours.

Note: the bath will be open to the atmosphere....not a closed system!

[rucik5]

Hi,
I think it largely depends on the oil. Some start to boil off slowly at 150, some go to 200 - don't know about 230. They also decompose slowly, especially when pushed to high temperatures. Either do a small test, check b.p. with the manufacturer or go for a heating mantle and a thermocouple. Wikipedia quotes 220 °C as the autoignition temperature for kerosene.

[Honclbrif]

If you need to keep it that hot for that long, try a sand bath

[poorstudent83]

The paraffin oil is "Heavy (68)".

I've tried the sand bath but it's not useful for larger quantities!!!

I've tried covering the sand bath with aluminium foil but it's never stable...

[Arctic-Nation]

I've successfully used silicon oil for shorter periods of time (up to 3 h) at about 230 °C. Something worth trying if you have some lying around.

(Entirely aside, 230 °C? Working with quinoline, perhaps?)

[fledarmus]

Sounds like a good time to switch to a microwave. Silicon oil would probably be okay if you didn't have to keep it there too long, but I wouldn't use a paraffin oil at those temperatures. The heating mantle is probably the best suggestion you've gotten so far.