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What is the solvent ?
3

What is the solvent ?

What is the solvent ?

(OP)

I was lately confronted with the issue of finding the solubility of water in pentane. A MSDS of normal pentane quoted data for water solubility at 20 deg C.

The question now is what is the solvent ? Does the statement mean "water in pentane" or "pentane in water" ? What is the norm or the custom in cases like this ?

RE: What is the solvent ?

I'm sure they meant "pentane in water."  I'm not sure that it makes a difference which way you call it, as long as you keep your concentrations straight.  I don't have any data to offer.

RE: What is the solvent ?

Pentane in water infers there is more water than pentane.
Water in pentane infers there is more pentane than water.

RE: What is the solvent ?

Perhaps...  but could you dissolve water in sugar?  The component being dissolved always undergoes a chemical change (dissociation), while the solvent doesn't, right?  (any chems care to butt in?)

Either way, if it's on an MSDS sheet, chances are good that they put the same field on every sheet, which means that "water solubility" means solubility in water (since table salt, sugar, and pentane would probably all have "water solubility" on the form).

RE: What is the solvent ?

2
Solute, Solvent, and Solution

It is important to distinguish between three closely related terms solute, solvent, and solution.

Solute – The substance that dissolves to form a solution
Solvent – The substance in which a solute dissolves
Solution – A mixture of one or more solutes dissolved in a solvent

RE: What is the solvent ?

Perhaps you can compare water solubility values from other MSDS's and figure it out.

RE: What is the solvent ?

If you do a Google search for solubility water pentane most of the hits are reprhased to pentane, solubility in water

... and according to Section 9 of http://www.jtbaker.com/msds/englishhtml/p0737.htm
Pentane is "insoluble in water"


Making the best use of this Forum.  FAQ559-716
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Helpful SW websites every user should be aware of.  FAQ559-520

RE: What is the solvent ?

From "The Handbook of Organic Solvent Properties", I.M. Smallwood, 1996 (ex. Knovel):
Solubility of Pentane in water = 39 mg/kg
Solubility of Water in Pentane = 120 mg/kg.

The first of those above is usually the one quoted and is far more readily available, and I suspect the one that was intended.  I agree that the phrase in the MSDS is ambiguous (and, incidentally, MSDS's are often an inaccurate source for physical property data).  

I disagree with IvyMike's comment that they are one and the same thing - as demonstrated by the data above.

RE: What is the solvent ?

So if you have 2.5kg of water, and 2.5kg of pentane, what happens when you combine them?

RE: What is the solvent ?

5.0 Kg of SOLUTION.

RE: What is the solvent ?

metengr,
Two stars, one for each post and both of them elegant answers.

RE: What is the solvent ?

I hate to bring in semantics, but this does seem to be the appropriate forum.  Based on the solubility data from TrevorP, I believe 2.5 kg of water plus 2.5 kg of pentane would be a heterogeneous mixture, or suspension.  A solution is a homogenous mixture, which is not the case for this pair.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: What is the solvent ?

(OP)

Corypad is right, apparently in their gaseous state -as vapors- these two would become a one-phase solution.

RE: What is the solvent ?

After further review, I would concur with CoryPad to assure correct semantics (including a star).

RE: What is the solvent ?

well, forgive me if this sounds dumb, but why wouldn't the mixture be homogenous?

RE: What is the solvent ?

Because the two liquids are not miscible (think oil and water). In general if 2 liquids are not miscible they will form a 2 phase mixture consisting (in this case) of water with a small amount of dissolved pentane, and pentane with a small amount of dissolved water. The state of the mixture will depend largely on mechanical agitation, and could be anything from two separate layers of liquid to an emulsion. The overall state will also depend on temperature.

Good Luck
johnwm
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RE: What is the solvent ?

thanks.

RE: What is the solvent ?

T capital.

Ciao.

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