Q: In my next mystery an amateur sleuth finds a stain on a wood floor under a rug. Is there a common substance she could use to determine if it were blood?
SCurran, Monroe, WI
A: There are a couple of easily obtainable chemicals that could be used for this. The first is phenolphthalein which was one of the first chemicals used to test for the presence of blood. It is readily available in most pharmacies and can be ordered online. There is a link below so you can see a company that sells the stuff and what it looks like.
Another thing that is purchased in any pharmacy are urine testing strips. These test for many chemicals but one of the things they test for the blood. There are several absorbent squares on the test strip one of which is a test for blood. Simply moistened the strip or moistened the staying and press the strip against the reaction will occur very quickly and this is a sensitive test for even small amounts of blood. Definitive testing to determine if it is indeed blood or if it is human blood or love a more sophisticated but these two testing methods are highly sensitive for even very small amounts of blood.