Why is it on CSI they use phenolphthalein to test for blood at crime scenes? That makes 0 sense to me because any basic solution anywhere would appear to be blood. At first I thought they were using something else, but I've heard them say phenolphthalein twice on the show. I thought to do a check for blood you would have to have something that show up with Iron from the hemoglobin.
2007-06-24 12:50:02 · 6 answers · asked by smilam 5 in Science & Mathematics ➔ Chemistry
If it helps any, the test is called the Kastle-Meyer test.. as to why doesn't it turn pink whenever it encounters any base in the environment, I guess there are 2 counter arguments
1. the pH isn't high enough.. there shouldn't be too many solutions in the general environment with a pH over 10.
2. maybe there is some way to distinguish blood splatter from other liquid spray
2007-06-24 13:06:30 · answer #1 · answered by Anonymous · 0⤊ 0⤋
"Phenolphthalein is used to perform a presumptive blood test, and is commonly known as the Kastle-Meyer test. A dry sample is collected with a swab or filter paper. First a few drops of alcohol, then a few drops of phenolphthalein and finally a few drops of hydrogen peroxide are dripped onto the sample. If the sample turns pink then it is a positive test. This test is nondestructive to the sample; it can be kept and used in further tests at the lab. This test has the same reaction with blood from any animal, so further testing would be required to determine whether it originates from a human."
2007-06-24 19:56:16 · answer #2 · answered by gp4rts 7 · 0⤊ 0⤋
This is an example of where a little knowledge is dangerous. The chemical is not actually "phenolphthalein", but is the reduced form "phenolphthalin". Phenolphthalein is refluxed for several hours in a concentrated sodium hydroxide solution with a zinc catalyst to form phenolphthalin.
2007-06-24 23:03:27 · answer #3 · answered by clanlabcooker 3 · 0⤊ 0⤋
It is used along with hydrogen peroxide in the Kastle - Meyr test for blood. (Although any peroxidase, such as those contained in saliva might yield positive to the test).
2007-06-24 19:58:31 · answer #4 · answered by Israfel 3 · 0⤊ 0⤋
I don't think that is the thing to pick on in the show.
What really needs to be addressed is the dna testing. In the shows, it appears to take maybe half an hour, when in reality it takes weeks.
wouldnt that make for more suspense?
2007-06-24 19:58:52 · answer #5 · answered by devinthedragon 5 · 0⤊ 0⤋
Check this out:
http://en.wikipedia.org/wiki/Kastle-Meyer_test
2007-06-24 19:55:14 · answer #6 · answered by Avi R 2 · 0⤊ 0⤋