A COLORIMETRIC METHOD FOR THE DETERMINATION

OF BUTYRIC ACID1

By sreeremya.sAsst professor,sree narayana guru

college,cbe

• 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.

• With ether as solvent, precipitates frequently form and invalidate

• the test.

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

cc. of 1 N HCl.

• 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

• 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.

• 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.