|Bruce (VA) said: (quoted from post at 10:03:49 08/05/14) " with the lighter components beginning to boil at temperatures below 100 degrees F "|
Isn't that called evaporation?
As was explained to me........
Ethanol boils at 172* F. Period.
Gasoline, however, will not really "boil" until around 200*.
So it's just a coincidence that frequent reports of gas boiling in N tanks has only been a recent (past 15 years or so) phenomena?
The "boiling point" of a liquid is the temperature at which it changes state from liquid to gas. Gasoline is a mixture of many different liquids and they boil at different temperatures.
In casual use, when we talk about a mixture boiling we are generally describing the state where visible gas bubbles are forming in the liquid and rising to the surface where the burst. That is not evaporation. Evaporation is a surface phenomenon where the molecules at the surface layer of a liquid reach the "boiling" temperature and change state to a gas. The gas molecules quickly coalesce into a partially saturated vapor - part liquid part gas. Only a very small percentage of the surface layer molecules do that at any given time and it is not generally detectable to the naked eye.
A moonshiner will tell you that ethanol "boils" at roughly 172F and water boils at roughly 212F. Consequently he can extract "pure" ethanol from a vat of fermented corn mash at temperatures right around 175F leaving the water and other byproducts behind. The ethanol gas is then passed through a condenser where it is cooled and turns back into "pure" liquid alcohol. That is "distillation". :D
As JMOR demonstrated you can produce visible "boiling" behavior in pump gasoline at temperatures well below the boiling point of ethanol (172F). In fact, if you look it up the boiling point of "gasoline" it is generally stated to be in the range of 100 to 400F. That doesn't mean different "gasolines" have different boiling points. It means the constituent parts of ANY gasoline blend have widely different boiling points. The individual components used to blend gasoline are refined from crude into their "pure" forms primarily through fractional distillation. After blending them into a new liquid mixture called "gasoline" you can extract them again using their boiling points and the process of distillation in just the same way a moonshiner makes "white lightning".
According to this 1999 publication (data from Shell) about 30% by weight of the hydrocarbons in unleaded pump gasoline have boiling points at or below 60C (140F). (nb. for some reason the YT bbcode software doesn't like the link but you can cut and paste to get to the document). The blending of pump gasoline has been an evolving science and that percentage may have changed slightly since the 40's but I don't think boiling gasoline in an N-series is a new phenomenon. The topic however has recently become red hot ;-)
TOH :D This post was edited by TheOldHokie at 09:02:43 08/05/14.