Question

You took 5ml phenol in a test tube and
added 3ml of 10 % NAOH and then few
drops of 1 % copper sulphate, but you did
not obtain the violet color, why?​

Answer 1

Answer:

When two drops of copper sulphate and ten drops of caustic soda or NaOH is added to egg, it turns violet. This indicates the presence of proteins.

This is Biuret's test and the principle is simple as follows:

In the presence of alkaline medium (caustic soda or NaOH), the Cu

2+

ions get reduced to Cu

+

and binds to the egg proteins, thereby giving a violet color.

Therefore, the correct answer is option B.