Just watching law and order and they said that bleaching a knife would still leave trace blood that could be detected by luminol.
Is that true? Why wont bleach clean it and is there anything that would?

On an episode of CSI they deleted blood trails of a case with bleach...

NsB


HOw do you become a real CSI anyway?

NsB

Yes it is true, luminol will detect blood from a cleaned surface, the only way to remove the blood completly would be to sand it --- grind off metal. I have used it.

What about acid, like vinegar? Or perhaps some kind of protien cleaner?
Luminol cant be unbeatable, nothing is.

Quoted: What about acid, like vinegar? Or perhaps some kind of protien cleaner? Luminol cant be unbeatable, nothing is.

No it is not, maybe with a shit load of scrubbing it would come clean, remember the metal under a microscope is full of holes and ridges, these collect and hold blood. Most people only clean off the blood they can see, leaving the minute paticles of blood in those ridges and holes that they cannot see. Hope this helps explain it.

Uh, what if you were to just burn the whole fucking house down?  Arson is a lot better than murder.

Tee-heee

What is luminol?

Quoted: Uh, what if you were to just burn the whole fucking house down?  Arson is a lot better than murder. Tee-heee

I have some stuff to clean you doofus.

Chemicals like ammonia or bleach won't remove blood entirely but they may contaminate it to the point where a test result becomes inadmissible or "suspect". Defense attorneys pounce on this.

Luminol is not a specific test for blood.  

By way of background, luminol is a chemical that when exposed to freshly made oxygen, also called nascent oxygen, is oxidized, and, in its intermediate excited state, will release photons in the visible spectrum.  Luminol is broken down in the process and is therefore not acting like a catalyst.  Hydrogen peroxide is broken down by many chemicals including iron complexes such as hemoglobin (in blood) to produce oxygen and water.  The nascent oxygen thus produced is able to oxidize luminol.  

If you have a solution of luminol and hydrogen peroxide and spray it on blood, it will glow.  Interestingly, the older the blood stain, the more effectively it breaks down hydrogen peroxide.  But many organic substances contain catalase or other similar enzymes that break down peroxide and can give false positive tests.  BTW, rust (iron oxide) will not break down peroxide.  

Luminol is useful to find 'hidden' bloodstains, and then more specific tests are used.  Bleach actually helps to break down the blood and won't prevent the reaction.  If you properly clean a knife blade with soap and water, you will get all the blood off.  Many killers simply don't clean blood from little crevices in the handle and get busted.

In college, I made a few batches of luminol from 3-nitro-phthalic acid and verified the above.  It is fun stuff to play with.

Quoted: In college, I made a few batches of luminol from 3-nitro-phthalic acid and verified the above.  It is fun stuff to play with.

Can you be more specific on how one can make it themselves? This would be excellent for tracking wounded deer.

Quoted: Quoted: In college, I made a few batches of luminol from 3-nitro-phthalic acid and verified the above.  It is fun stuff to play with. Can you be more specific on how one can make it themselves? This would be excellent for tracking wounded deer.

I don't have the lab preparation in front of me, but off the top of my head:  you reflux 3-nitro-phthalic acid or its anhydride with hydrazine hydrate and propylene glycol.  The product is 3-nitro-phthalhydrazide.  This is then reduced with sodium hydrosulfite to 3-amino-phthalhydrazide which is luminol.  It is easier to buy it unless you are particularly adept in a chem lab, not to mention all the chemicals you need.  I haven't searched for luminol, but I'm sure it can be bought.  If you're serious, I'll be happy to tell you how to mix up the solutions.  You'll also need a small amount of sodium hydroxide.  

Quoted: HOw do you become a real CSI anyway? NsB

On the news today they were reporting that ever since the show CSI came out, there has been such an interest in jopining that now the schools are overcrowded that there arent enough jobs out there for the ones that are graduating.

Now only if they made a show about refrigeration technicians. I can hire someone!!!!

Quoted: What is luminol?

Here's a rather lengthy cut & paste explaination;

"Luminol"


5-amino-2,3-dihydro-1,4-phthalazine-dione, or luminol has become a commonly used, and functional compound.  Luminol is a relatively simple chemical containing only carbon, nitrogen, oxygen and hydrogen.  It was discovered in the late nineteenth century and later improved upon.  Luminol is used often in biochemistry and serves many purposes from Halloween fun to crime scene blood detection.

     Luminol, (C8H7N3O2) has quite a few other names; these include: 5-amino-2,3-dihydro-1,4-phthalazine-dione, o-aminophthalyl hydrazide, 3-aminophthathic hydrazide, and o-aminophthaloyl hydrazide1.  Its molecular weight is 177.16, and has a melting point of 319ºC-320ºC.  Its solubility is less than 0.1grams per 100 milliliters at 19ºC, and looks like a yellow grainy substance.  If reacted the luminol emits a green-blue light with varying intensity.  

           Luminol is a chemiluminescent compound, which means that a release of light is a result of a chemical reaction2.  Fireflies are nature’s chemiluminescent creatures, they create a similar reaction to produce their own light source,(which can be seen at night in more rural areas.) This light is energy being released.

           When luminol is placed in a basic solution such as perborate, permanganate, hyperchlorite, iodine, or hydrogen peroxide, and a catalyst such as iron, manganese, copper, nickel, or cobalt, the luminol is oxidized2.  (A catalyst is the most important ingredient to the reaction, because the stronger the catalyst, the longer and brighter the light will glow.)  Most metals aid in the reaction, but there are a few that actually repress the response2.  Hydrogen peroxide works best as the base, it “burns” the luminol.  Cobalt has proven to be the best metal catalyst2.  The luminol creates light via oxidation, because the two nitrogen atoms are easily replaced by two oxygen atoms.  As this reaction occurs, nitrogen gas is discharged, leaving the luminol in an excited state, with additional energy which is then released as light3.  Amino acids, tegatose, fructose, glycerols, thiols, and serum albumin can also react with luminol to produce an intense light.  No excitation source is needed to produce a glow, but a photomultiplier tube may be used to measure and detect the amounts of light2.  

           In 1895, two scientists named Wiedemann and Schmid, dissolved cathode-ray irriaded alkali halides such as NaCl, NaBr, KCl, and KBr, in water.  They noticed a very weak bluish light.  They also detected light production when irriaded calcium carbonate was “attacked” by aqueous hydrochloracetic acid, or phosphoric acid4.

           Later in 1928, a chemist by the name of Albrecht discovered a specific chemical, that when placed in an aqueous alkaline solution emitted a blue-green light with a fair amount of intensity.  Along with the light, virtually no heat was produced.  This solution contained hydrogen peroxide along with a catalyst.  The catalyst was an alkaline medium with a pH between ten and eleven.  This specific chemical was to later on be called luminol5.  

           Albrecht also determined the maximum intensity of light in this new chemical to be 424nm; he also concluded that fresh luminol was very unstable in its light yield, and the light yield itself came from the dissolved oxygen, and favored a trace metal.  These discoveries led to a compound that created a useful cold light source at relative ease5.

           Halloween has always been a night of excitement for children, a night when they can pretend to be anything, and a night full of sugar.  Many children carry green glow-sticks on Halloween to illuminate themselves for safety purposes.  These light-sticks contain dilute H2O2 in a phthalic ester solvent in a capsule.  This is the surrounded by a phenyl oxalate ester and 9,10-bis(phenylethynl) anthracene.  When snapped, these two chemicals combine to produce luminol.  The glow-sticks are green, because of other chemicals.  At other events (such as fairs) multi-colored necklaces and bracelets are seen, and use this same type of compound to create their glow6.

           Often, luminol is used in biology and biochemistry for a multitude of testing.  Chromatography, (which is a method for sorting chemical substances) immunoassay, (measures minute concentrations of biological matter in blood) DNA probes, and DNA fingerprinting, all use luminol as a testing reagent, and it is used as a substrate in western blot detection7.

           The most important and well-known use of luminol is in the field of forensic science.  In 1937, a German forensic scientist, discovered the use of luminol in blood detection8.  Blood, which is slightly alkaline, contains cells, water, enzymes, proteins, and hemoglobin9.  Hemoglobin (which contains iron) carries oxygen to parts of the body.  This hemoglobin reacts with the luminol as the catalyst10.  Luminol can detect very small amounts of blood many years old.  

           Once an area is suspected to have blood (even if the area has been cleaned) luminol can be applied.  The lights are turned out, and after a brief few seconds (approximately five seconds,) a glow may appear.  Just because an area glows, does not necessarily mean blood is the culprit.  Bleach, dyes, and other organic material can react with the luminol.  For the most part, luminol is a very useful tool in murder and rape investigations9.  Luminol has helped put many murderers and rapist in prison, when evidence seemed to be hidden.

           Just because it can trace minuscule amounts of blood at an efficient manner, does not mean that it does not have any drawbacks in crime scene investigation.  Because it can detect other chemicals and compounds, further testing is almost always required to determine if the reactant is blood.  If so, then the process begins to establish the type of blood, and if it is the victim’s blood.  If luminol is used, it can break down and cause a loss to several genetic markers used in genetic testing as well as destroy other important properties of the blood.  While it can detect even small amounts of blood, the disadvantage is often that the small amount identified is diluted further by the luminol solution.  For these reasons, luminol is encouraged to be used as a last resort in crime scenes to protect what little physical evidence there already is9.  

           The chemiluminescent properties of luminol are remarkable in the fact that instead of heat, reactions involving luminol produce a cool light that has become a useful tool for both the scientific community and average individuals.  It has aided research in blood.  Luminol has helped to make the world a safer place by aiding the forensic community in its investigations.  It has helped to further genetic testing via DNA probes, and medical testing, and has created an relatively safe natural light that can be seen anywhere on Halloween night.

Quoted: Quoted: Quoted: In college, I made a few batches of luminol from 3-nitro-phthalic acid and verified the above.  It is fun stuff to play with. Can you be more specific on how one can make it themselves? This would be excellent for tracking wounded deer. I don't have the lab preparation in front of me, but off the top of my head:  you reflux 3-nitro-phthalic acid or its anhydride with hydrazine hydrate and propylene glycol.  The product is 3-nitro-phthalhydrazide.  This is then reduced with sodium hydrosulfite to 3-amino-phthalhydrazide which is luminol.  It is easier to buy it unless you are particularly adept in a chem lab, not to mention all the chemicals you need.  I haven't searched for luminol, but I'm sure it can be bought.  If you're serious, I'll be happy to tell you how to mix up the solutions.  You'll also need a small amount of sodium hydroxide.

Uh....yeah....OK....I will get right on that.  Guess I should have paid better attention in Chemistry, eh?  Off the top of your head even...your head muist be filled with lots of....um....interesting things.

It sounds like the exact same stuff in the Calumlight sticks. Anybody know for certain?

Quoted: It sounds like the exact same stuff in the Calumlight sticks. Anybody know for certain?

No.  The luminol reaction is much too brief to be used in Cyalume sticks.  I've read what it is at some point.

Quoted: Uh....yeah....OK....I will get right on that.  Guess I should have paid better attention in Chemistry, eh?  Off the top of your head even...your head muist be filled with lots of....um....interesting things.

You have no idea.

Quoted: It sounds like the exact same stuff in the Calumlight sticks. Anybody know for certain?

Light sticks contain diluted H2O2 in a phthalic ester solvent in a capsule. This is then surrounded by a phenyl oxalate ester and 9,10-bis(phenylethynl) anthracene. When snapped, these two chemicals combine to produce luminol.

I already knew that ammonia can contaminate blood to the point that it is untestable, because I saw the vigilantes in Boondock Saints use it to clean up their own bloodstains after a particularly heavy gunfight.

Quoted: Quoted: In college, I made a few batches of luminol from 3-nitro-phthalic acid and verified the above.  It is fun stuff to play with. Can you be more specific on how one can make it themselves? This would be excellent for tracking wounded deer.

No it is not cool to play with --- is is listed as a carcinogen.

Quoted: I already knew that ammonia can contaminate blood to the point that it is untestable, because I saw the vigilantes in Boondock Saints use it to clean up their own bloodstains after a particularly heavy gunfight.

Wow- now that's what I call incontrovertible proof. Now I know where to get my scientific, historic, and political instruction: Hollywood! After all, if it's on TV or in a movie it must be true, right? Hollywood would never lie to us, right?

95th ("As Seen On TV!") Foot

Quoted: Quoted: Quoted: In college, I made a few batches of luminol from 3-nitro-phthalic acid and verified the above.  It is fun stuff to play with. Can you be more specific on how one can make it themselves? This would be excellent for tracking wounded deer. No it is not cool to play with --- is is listed as a carcinogen.

I didn't say we should start mixing it with baby formula.  I'll re-phrase:  if you follow all the safety rules in the lab, then it is an interesting chemical to experiment with.  BTW, there are few chemicals in an organic chemistry laboratory that are not listed carcinogens.

So true.