Agglutination occurs in blood present in a test tube. This indicate

Under what circumstances does agglutination occur during blood tranfusion even if the donor and recipient both have the same blood group ?

Blood clotting can be prevented in a test tube by adding a little

You are given two colourless solutions present in two test tubes. One out of these is ethyl alcohol and the other is acetic acid. Give three tests to identify these.

A student was given an unknown solution in a test tube. When he added universal indicator solution to the test tube the solution turned violet. The unknown solution is most likely to be: