Chromic (Synaptic Self-Mutilator)
10-15-03 06:25
No 464696
      Extraction mathematics     

Okay, so there wasa solution of GBL in 500ml acidified brine. I'm guessing (???) that there was approximately 120g to be extracted from the mixture.

Experimental results
3x150ml extraction with DCM and got 94.2g crude.
3x150ml extraction with DCM and got 21.0g crude.

Can anyone tell me what the breakdown of each of the 6 extractions would be?

I'm thinking it would be like:

The first extraction, there was ~120g present and 40% of it partitioned to the DCM. So 48g was extracted into the DCM and 72g remains in the water. ie:

1) 120g present, 48g extracted
2) 72g remains, 29g extracted
3) 43g remains, 17g extracted
4) 26g remains, 10g extracted
5) 16g remains, 6g extracted typo fixed: thanks Vitus
6) 9g remains, 4g extracted

So for the first three, we have 94g extracted, for the second three we have 20g extracted. Then if there was another 3, there would have been 4g in total extracted (waste of time, really)

Does this make sense or do I have my physical chemistry wrong?
 
 
 
 
    Vitus_Verdegast
(Hive Bee)
10-15-03 07:22
No 464709
      yup     

That should be correct.

(if not, I should also better restart with these courses wink)


btw --> 5) 16g remains, 6g extracted  typo

A Dream Within A Dream (http://www.poedecoder.com/Qrisse/works/dreamw.html)
 
 
 
 
    Rhodium
(Chief Bee)
10-15-03 19:07
No 464818
      Ref for extraction distribution calculations     

Post 453799 (Rhodium: "Theory of Extraction", Newbee Forum)

Now, what is the partition coefficient for butyrolactone between brine and DCM? Calculating that could be useful for future endeavors in this field.
 
 
 
 
    Chromic
(Synaptic Self-Mutilator)
10-16-03 02:25
No 464877
      Okay, more guessing     

Okay, so if my numbers are correct.. and I'm sure that they are not out by an order of magnitude... let's see.

Of 120g GBL in the first extraction... there's 72g GBL in 500ml acidified brine and 48g in 150ml DCM.

Kp = (solubility in organic)/(solubility in aqueous)

So Kp = (48/150)/(72g/500ml)
Kp = 2.2

Which should match for all of them...

(29/150)/(43/500)

Kp = 2.2

And sure enough, it does match. Does that make sense? Of course there's no way to get the maximum solubility of GBL in DCM or water because they're miscible... now I suppose my next question is, is there a better way to do the extractions to use less DCM and get more product? (i.e. a more efficient way of doing the 5 extractions?)

Btw, speaking of solubilities and GBL/GHB... does anyone know the solubility of NaGHB in water? Both as solution volume and volume of water... and hell, density info would be fantastic too)
 
 
 
 
    Chromic
(Synaptic Self-Mutilator)
10-16-03 02:43
No 464879
      More fun with math
(Rated as: good read)
    

Kp = sol in dcm / sol in aq

let x = # of grams in DCM
let t = total # of grams
let k = Kp
let d = volume of DCM
let a = volume of aqueous

k = (x/d)/((t-x)/a)

So then:

x = kdt/(kd+a)

Setting up a quick Excel spreadsheet... predicts... that optimally... all of the extractions should be of the same size! DOH! I've always wondered if it would be better to use more for the first, less for the second, or vice-versa. Okay, question answered. Maybe I should be writing in the newbee forum from now on.