The Quantitative Precipitin Technique is a simple technique that is routinely used in the analysis of antibody and antigen interactions and for the estimation of the antibody or antigen content in a sample.  The technique is based on the interaction of antibody and antigen to form a large protein complex that in certain solutions (buffer) will result in precipitation. Students undertake a simple experiment to determine the zone of equivalence of an antigen and antibody interaction.  The kit is provided with a fluorescent labeled protein to make visualization of the results clearer and easier to compare.