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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: themonk on June 28, 2012, 02:14:40 PM

Title: Formula clarification
Post by: themonk on June 28, 2012, 02:14:40 PM
I have a formula for a precipitant but don't follow what it exactly means.  

"Cooling the concentration solution to room temperature would cause precipitation of the double salt Na7F(PO4)2*19H2O."

What I do not understand is the "*19H2O". What exactly is the meaning of it? Where would all that water be located (evaporated, surrounding molecule)?

If this should be in Undergraduate Chemistry, please move it.

Cheers

Edit: I think I have also noticed when discussing crystallization.
Title: Re: Formula clarification
Post by: discodermolide on June 28, 2012, 02:18:35 PM
Quote from: themonk on June 28, 2012, 02:14:40 PM
I have a formula for a precipitant but don't follow what it exactly means.  

"Cooling the concentration solution to room temperature would cause precipitation of the double salt Na7F(PO4)2*19H2O."

What I do not understand is the "*19H2O". What exactly is the meaning of it? Where would all that water be located (evaporated, surrounding molecule)?

If this should be in Undergraduate Chemistry, please move it.

Cheers

Edit: I think I have also noticed when discussing crystallization.


The water is in the crystal lattice, water of crystallisation.
Title: Re: Formula clarification
Post by: Borek on June 28, 2012, 02:19:58 PM
http://en.wikipedia.org/wiki/Water_of_crystallization

Edit: Disco beat me.

Note: it should be be not an asterisk, but a middot: NaF(PO4)2ยท19H2O.