# Liquid–Liquid Extraction Calculator - Partition Coefficient, Multiple Extractions, pH and Distribution Ratio

> Free extraction calculator: single vs multiple extraction recovery from KD, distribution ratio vs pH, acid–base separation, countercurrent and layer order.

- URL: https://qilingtools.com/en/chemistry/extraction
- Category: Chemistry Tools (https://qilingtools.com/en/chemistry)
- Tags: [Chemistry](https://qilingtools.com/en/tags/chemistry)
- Last updated: 2026-10-29
- Price: Free, no sign-up
- Privacy: Runs locally in the browser; files are never uploaded

In liquid–liquid extraction a solute distributes between the organic and aqueous phases according to the partition coefficient K_D = c_org / c_aq. Extracting V_aq of aqueous solution once with V_org of solvent leaves a fraction q = V_aq / (V_aq + K_D·V_org) in the water, and n extractions leave qⁿ. With K_D = 4 and 100 mL of water, one extraction with 90 mL leaves q = 100/(100 + 360) = 0.217 (78.3% extracted), while three 30 mL portions leave (100/220)³ = 0.0939 (90.6% extracted) — the classic reason to use several small portions. The tool plots recovery against the number of portions for the same total solvent, shows the n → ∞ limit e^(−K_D·V_org/V_aq), and finds how many extractions reach a target recovery. For weak acids and bases only the neutral form enters the organic phase, so the distribution ratio depends on pH: D = K_D / (1 + 10^(pH − pKa)) for an acid and D = K_D / (1 + 10^(pKa − pH)) for a base. Benzoic acid (pKa 4.20) with K_D = 100 has D ≈ 0.158 at pH 7, so it stays in the water as benzoate. A log D–pH chart gives the pH to extract into the organic layer or back-extract into water. The acid–base separation view computes how ionised benzoic acid, phenol, aniline and naphthalene are in HCl, NaHCO₃ and NaOH washes and explains why bicarbonate comes before hydroxide. Also included: Craig countercurrent distribution (binomial tube distribution, separation factor β = D₁/D₂, resolution) and a separatory-funnel diagram showing which layer is on top from solvent density (dichloromethane 1.33 at the bottom; ether 0.713 and hexane 0.655 on top).

## How to use

1. Choose a mode: multiple extractions, pH & distribution ratio, acid–base separation, Craig countercurrent or layer order
2. Enter the partition coefficient, phase volumes and number of portions, or pick a solute, pH or organic solvent
3. Read the recovery, chart, working and recommendations; export charts or copy results

## Features

- Single vs split extractions with the n → ∞ limit
- Number of extractions for a target recovery and amount removed per step
- log D vs pH for weak acids and bases with pH recommendations
- pKa values shared with the site’s pH calculator (benzoic acid, phenol, aniline, pyridine…)
- Benzoic acid / phenol / aniline / naphthalene separation scheme with ionisation table
- Craig countercurrent binomial distribution, separation factor β and resolution
- Separatory funnel diagram: organic layer on top or bottom by density
- Export charts as PNG, SVG or CSV

## FAQ

### Why are several small extractions better than one large one?

One extraction leaves q = V_aq/(V_aq + K_D·V_org) in the water. Splitting the same volume into n portions leaves [V_aq/(V_aq + K_D·V_org/n)]ⁿ, which is always smaller. With K_D = 4, 100 mL of water and 90 mL of solvent in total, one extraction recovers 78.3%, three portions 90.6%, and even infinitely many only approach 1 − e^(−3.6) = 97.3%. The gain shrinks with each extra portion, so about three is typical.

### What is the difference between the partition coefficient K_D and the distribution ratio D?

K_D is the concentration ratio of one species (usually the neutral molecule) between the phases and does not depend on pH. D is the ratio of total concentrations of all forms — what you actually measure. For a weak acid HA, the water also holds A⁻, which does not enter the organic phase, so D = K_D/(1 + Ka/[H⁺]). Two pH units below the pKa D ≈ K_D; two units above it D is only about 1% of K_D.

### How do you separate benzoic acid, phenol, aniline and naphthalene by extraction?

Dissolve the mixture in ether. Wash with dilute HCl: aniline (conjugate acid pKa 4.6) goes into the water as its salt. Wash with NaHCO₃ (pH ≈ 8.3): benzoic acid (pKa 4.20) becomes sodium benzoate, while phenol (pKa about 10) is only about 2% ionised and stays organic. Wash with NaOH to remove phenol as phenoxide. Naphthalene remains in the ether. Acidify or basify each aqueous extract to recover each compound.

### Is the organic layer on top or on the bottom?

Compare densities: lighter than water floats, heavier sinks. Dichloromethane (1.33 g/mL), chloroform (1.49) and carbon tetrachloride (1.59) are on the bottom; diethyl ether (0.713), ethyl acetate (0.902), hexane (0.655) and toluene (0.867) are on top. Saturated brine (about 1.2 g/mL) or heavily loaded layers change the densities, and water-miscible solvents such as ethanol, acetone, acetonitrile and THF cannot be used to extract an aqueous solution.

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