Author Topic: 30% H2SO4  (Read 3288 times)

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Elementary

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Re: 30% H2SO4
« Reply #20 on: March 07, 2002, 11:49:00 PM »
I agree with you, it does not seem logical for the density to go down as the concentration goes up at the end of the scale.

Unfortunately it is the only ref I can find, searching with webferret brought nothing up but single densities on datasheets that don't even state the temperature it was measured at.

I just find it strange that there is this oddity with the oleum densities as well. Maybe they had SO3 bubbles clinging the the hydrometer, the book was printed in 1954.



Umm, how interesting !!

Mountain_Girl

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Re: 30% H2SO4
« Reply #21 on: March 08, 2002, 08:53:00 AM »
Unfortunately I can't explain why it happens (chemistry resembles voodoo sometimes) , but the density peak is for real.
Ullman's Encyc. of Ind. Chem. says:

'At constant temperature, the density of sulfuric acid increases steeply with rising H2SO4 concentration, reaching a maximum at about 98 %. From there up to a concentration of 100 % the density decreases slightly, but it rises again in the oleum range up to a concentration of ca. 60 % free SO3.'

Also I have table of densities at 20°C issued by a company which shows the same trend.

I neglected to mention in my previous post that using density as an indicator of composition is only useful up to about 95% H2SO4 for this reason. That is, if you measure a density of 1.838 say, then it could be either 100% or about 94% H2SO4 - you wouldn't know.

[That was nicely spotted Archaeoptrix.]

Elementary

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Re: 30% H2SO4
« Reply #22 on: March 08, 2002, 09:06:00 PM »
Thanks for that Mountain_Girl !!  :)

Umm, how interesting !!