Precipitation Reaction of Proteins

Proteins can be precipitated by heating. The experiment uses three test tubes with egg albumin. One test tube has 0.1 normal acetic acid, another has 5 normal acetic acid, and the third is a control without acid. All three are heated in a water bath to observe the effects of heat and acidity on protein precipitation.

This method involves adding 4ml of ethyl alcohol to 2ml of egg albumin. The formation of a precipitate is observed. A portion of the precipitate is then tested for solubility in water. The remaining mixture is set aside for 30 minutes, after which the precipitate's solubility in water is re-evaluated. The filtrate from the remaining mixture is also heated to observe further changes.

Proteins can be precipitated by neutral salts. Two test tubes with 2ml of egg albumin each are used. One is saturated with sodium chloride, and the other is saturated with ammonium sulfate. The differences in precipitation between the two salts are observed.

This method demonstrates protein precipitation using a heavy metal. 1ml of cupric sulfate solution is added to 2ml of egg albumin to observe the formation and color of any precipitate.

The final method involves using an alkaloidal reagent, picric acid. To 2ml of egg albumin, one drop of hydrochloric acid solution is added first, followed by two drops of picric acid solution. The resulting precipitate's formation and color are observed.