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55 comments on It's Time for Summer Gasoline

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elwoodelmore on April 16, 2008 - 11:27am Permalink | Subthread | Comments top

"Butane, which has an RVP of 52 psi, can be blended into gasoline..."

but were it not for the other heavier components in gasoline, butane would leave the scene running, winter or summer. would you please comment on this ?

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memmel on April 16, 2008 - 11:41am Permalink | Subthread | Parent | Comments top

I think your asking why it stays in the gasoline. The simple answer is its soluble in the other components. This lowers whats called the partial vapor pressure. A example is a carbonated drink obviously C02 is a gas but its soluble in water and forms complex with it. This does slowly leak out at room temperature but as you know from experience a carbonated drink can taste bubbly for quite a while after opening.

Solubility itself is just a type of fleeting chemical bonding quite similar to say balls of velcro being tumbled around. The solute sees the solvent as "sticky".

Sorry I'm not sure you where asking a question and I'm not sure how much chemistry you know.

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elwoodelmore on April 16, 2008 - 11:49am Permalink | Subthread | Parent | Comments top

this problem has plagued oil reservoir engineers since the science was invented.
most of them simply treat every oil as a "black oil" (composed of methane which obeys the real gas law and heavy components which are liquid in the reservoir and stock tank). compositional models dont seem to get the job done either.
back in the old days, that was the mid '70's, texaco used fugacity(sp?)to try to calculate the part that would be liquid, that didnt work either.

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skorpela on April 16, 2008 - 12:36pm Permalink | Subthread | Parent | Comments top

Here is the explanation of Raoult's law and vapor pressure in ideal and real solutions.

Raoult's Law

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DIYer on April 19, 2008 - 5:33pm Permalink | Subthread | Parent | Comments top

Precisely.

If 10% of the molecules are butane, the vapor pressure of the resulting solution will be 10% that of pure butane, plus 90% of whatever pressure is contributed by other ingredients (of lower VP). There will be some deviation from this idel, but I believe hydrocarbons are pretty close to theoretical.

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elwoodelmore on April 20, 2008 - 6:40am Permalink | Subthread | Parent | Comments top

hydrocarbon mixtures probably behave as ideal components at relatively low temperature and pressure (i.e. atmospheric). not true at higher temperatures and pressures.

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55 comments on It's Time for Summer Gasoline

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