# Heating a sealed glass bottle of liquid from 20'C to 90'C

1. Jan 8, 2012

### science squir

Hi
I have people heating liquids in sealed glass Schott bottles in our lab if they cannot find any metal containers in our lab. These are 1 liter bottles they are approximately filling to 500ml with very aqueous solutions.
The bottles have not actually broken one, but Schott advises not to apply pressure to glass bottles.
What is the actual pressure inside the sealed glass bottle once it is heated to 90'C from 20'C?

Are there three things to consider?

1/ The Boyle gas law where PV/T = PV/T
So approx P of gas after heating is = ( 1atm * 363K ) / 293K = 1.23atm.
(I am assuming that in a closed glass container that the volume of the gas would not change significantly)

2/ The aqueous solution would expand by the thermal expansion of water. 500ml. Water thermal expansion coefficient of 206x10*-6 / 'C. From 20'C to 90'C. So the expansion is only about 0.07ml. So maybe not such a big influence on the pressure.

3/ Vapour pressure graphs for water show no increase in Vapour pressure until 100'C. I would have thought there would be some increase in pressure with evaporation of water below 100'C in a closed container?

So does that mean that the pressure has increased to approx 1.23atm within the sealed glass container with 500ml of aqueous solution heated from 20'C to 90'C?

Thanks

2. Jan 9, 2012

### Dr_Morbius

The vapor pressure of water is ~525 mm Hg at 90°C so I don't know what graphs you used but they were wrong. But other than that your calculations are correct.

3. Jan 9, 2012

### science squir

That is great. Thanks!! I was reading the vapour pressure as Absolute not gauge, so that was my bad...

4. May 6, 2012