June 1, 2012
Somebody actually asked me how luminol reacts with blood, and as my close friends know, a single question is enough to set me on a massive lecture. Many thanks to the Anthro Med Library for their wonderful picture of the oxidation (electron loss) of luminol, which, if anyone is curious, is used in an article on a “Chemiluminescence Assay of H2O2 Production by Neuroblastoma Cells Stimulated with High Potencies of the Cytotoxin TNFalpha”, of which I have only a vague concept of what that means. 
But what we’re concerned with is luminol. Essentially, a testing kit for blood is a solution of luminol, a strong base like potassium hydroxide, and hydrogen peroxide. What I mean by “strong base” is that in water it completely breaks up into a positive potassium ion (K+), and a negative hydroxide ion (OH-). Luminol reacts with hydroxide in an equilibrium reaction to remove the H from the two -NH groups, making two -N- groups. There is an equilibrium with this molecule (called a dianion because it has two negative charges) and another, where the negative charges are on the two oxygens. 

Hydrogen peroxide decomposes slowly into water and oxygen, which means that over time the luminol solution will go bad, because oxygen reacts with the second dianion to make the “amino phthalat” seen in the opening image, which releases nitrogen gas and a photon (which is what the hv means). When the solution is sprayed onto blood, however, the iron in hemoglobin (the molecule in blood that moves oxygen) catalyzes the decomposition of hydrogen peroxide, so suddenly there’s a lot of oxygen that can react with the dianion. Lots of oxygen means lots of the “amino phthalat”, meaning lots of photon. All the CSI guys have to do now is close the shutters and find the glow. 
It’s not perfect, mind you. Many other metals catalyze the reaction, copper, manganese dioxide, to think of two, and certain chemicals (like bleach) can make the reaction go as well. 
This post is brought to you by M. Alice, who probably now knows that I’m much better at chemistry than the history of Renaissance authors. 

Somebody actually asked me how luminol reacts with blood, and as my close friends know, a single question is enough to set me on a massive lecture. Many thanks to the Anthro Med Library for their wonderful picture of the oxidation (electron loss) of luminol, which, if anyone is curious, is used in an article on a “Chemiluminescence Assay of H2O2 Production by Neuroblastoma Cells Stimulated with High Potencies of the Cytotoxin TNFalpha”, of which I have only a vague concept of what that means. 

But what we’re concerned with is luminol. Essentially, a testing kit for blood is a solution of luminol, a strong base like potassium hydroxide, and hydrogen peroxide. What I mean by “strong base” is that in water it completely breaks up into a positive potassium ion (K+), and a negative hydroxide ion (OH-). Luminol reacts with hydroxide in an equilibrium reaction to remove the H from the two -NH groups, making two -N- groups. There is an equilibrium with this molecule (called a dianion because it has two negative charges) and another, where the negative charges are on the two oxygens. 

Luminol Dianions

Hydrogen peroxide decomposes slowly into water and oxygen, which means that over time the luminol solution will go bad, because oxygen reacts with the second dianion to make the “amino phthalat” seen in the opening image, which releases nitrogen gas and a photon (which is what the hv means). When the solution is sprayed onto blood, however, the iron in hemoglobin (the molecule in blood that moves oxygen) catalyzes the decomposition of hydrogen peroxide, so suddenly there’s a lot of oxygen that can react with the dianion. Lots of oxygen means lots of the “amino phthalat”, meaning lots of photon. All the CSI guys have to do now is close the shutters and find the glow. 

It’s not perfect, mind you. Many other metals catalyze the reaction, copper, manganese dioxide, to think of two, and certain chemicals (like bleach) can make the reaction go as well. 

This post is brought to you by M. Alice, who probably now knows that I’m much better at chemistry than the history of Renaissance authors. 

March 29, 2012

This is one of the more boring bits of this page, but I thought it was interesting. This is a video about the phenomenon of “supersolidity”, where solids (particularly helium) don’t move as one mass, like nearly every other solid does. For a low-tech image, imagine shaking a disk of helium-4. Because this is hypothetical, your hand doesn’t immediately freeze because helium-4 is solid only at extremely low temperatures ( Beween 0 and 1 degree K, and perhaps pressures greater than normal atmospheric). When you shake it in one direction and stop it abruptly, most of the molecules will stop as well. A few of them, however, around 1% according to the study, will move a bit further, breaking and remaking the bonds between clusters of helium-4 molecules like it ain’t no thang. 

Is it earth-shattering? Not by any stretch of the imagination, no, considering that scientists aren’t entirely sure it actually exists, but it does expand on how we think things work. The bigger question is whether or not we’re right. Here’s hoping we are. 

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