This document describes a colorimetric method for determining the concentration of butyric acid in a solution. The method involves converting the butyric acid to its copper salt derivative using copper chloride and hydrochloric acid. The copper butyrate is then extracted with ether or chloroform, imparting a blue color to the organic layer. The intensity of the blue color corresponds to the concentration of butyric acid in the original solution. Standard solutions of sodium acetate and sodium butyrate are prepared and mixtures of the two are used to generate a calibration curve relating color intensity to concentration.

1. A COLORIMETRIC METHOD FOR THE
DETERMINATION
OF BUTYRIC ACID1
By sreeremya.s
Asst professor,sree narayana guru
college,cbe

2. • The general principle of Agulhon's test is to
convert butyric
• acid into its copper salt and to extract this with
ether. The
• copper butyrate imparts a blue color to the ether
layer. The
• degree of color varies with the concentration of
butyrate, the
• acidity of the solution and the quantity of copper
salt used.

3. • With ether as solvent, precipitates frequently
form and invalidate
• the test.

4. • Reagents
• 1. Copper chloride-hydrochloric acid reagent.
• Dissolve 85.26 grams of CuCl2 2H20 in 1000
cc. of 1 N HCl.

5. • 2. Chloroform-C. P.
• 3. Standard color tubes.
• Make up half normal solutions of sodium acetate and
sodium
• butyrate as follows:
• Dilute 3 grams of glacial acetic acid with 20 cc. of water and
• neutralize to phenolphthalein with 1 N NaOH. Dilute the
• resulting sodium acetate solution to twice the volume of
the 1 N
• NaOH used. This gives a solution of exactly 0.5 N strength.
• Redistill butyric acid (Eastman Kodak Company) and collect

6. • the fraction boiling between 161 to 162°C.
Dilute 4.4 grams of
• this distillate with water and treat in the same
manner as above
• to give a 0.5 N strength solution of sodium
butyrate.

7. • Mixtures of these two solutions are made as indicated in
• table 1. The combinations are made in a separatory funnel and
• to each combination 0.4 cc. of CuCl2-HCl reagent are added and
• the mixture shaken. Five cubic centimeters of chloroform are
• then added and shaking continued until a maximum color develops
• in the chloroform layer (twenty to thirty seconds). After
• the chloroform layer has settled it is drawn off into test tubes of
• uniform diameter and closed with a well-fitting cork of good
• quality.