ExtractionExtraction is a general theory for the recovery of a substance

from a mixture by bringing it into contact with a solvent which preferentially dissolves the desired material. In organic

chemistry, the reaction product is frequently obtained as a solution in water along with other organic and inorganic

byproducts.

Let’s get started

• To begin this lesson, click on the web address below and view this first 12 pages.

• http://www.slideshare.net/Atharsaeedi/extraction-theory

• Return to this powerpoint after viewing the first 12 pages.

Let’s do the math

By definition, the distribution coefficient is:

concentration in the organic layerconcentration in the water layer

Let us consider compound A:10g of compound A will dissolve in 100ml ethyl ether (an organic compound)2g of compound A will dissolve in 100ml of water

Calculate the KD for compound A

KD=

Determining the KD

concentration in the organic layer = 10g/100ml

concentration in the water layer 2g/100ml

KD= 5

If you are given a solution of 1g of compound A dissolved in 100ml of water, how much could you extract if you did three extractions using 25ml of ethyl ether with each extraction?

KD=

Set up the problem

Solve for X by cross multiplying two times. Go to the next page to see the value for X.

X = 0.556g

• This means that 0.556g of compound A has now moved to the ethyl ether layer.

• How much compound A remains in the water?• 1g – 0.556g = 0.444g of compound A in the

water.• Now set up the problem for the next

extraction:

2nd Extraction

Cross multiply twice and solve for X.

X=0.247g

• This means that 0.247 more grams of compound A have moved from the water layer to the ethyl ether.

• How much compound A remains in the water?• 0.444g-0.247g = 0.197g of compound A are

still in the water.• Set up the problem for the third extraction.

3rd Extraction

Solve for X and you should obtain X = 0.109g of compound A.

What is the total amount of compound A extracted?

0.556g + 0.247g + 0.109g = 0.912g extracted in the ethyl ether.

1g – 0.912g = 0.88g of compound A remaining in the water.

Try another problem?

• 15g of compound J dissolves in 100ml of benzene.

• 5g of compound J dissolves in water.• You are given a solution with 2g of compound

J dissolved in 100ml of water. If you do two extractions with 50ml of benzene in each extraction, how many grams of compound A can you extract from the water?

Solve for KD and 1st extraction

2nd extraction and final answer