@jpanhalt mentioned this in a post and it reminded me that I have heard of it several times and know very little.

I saw a TV show about explosives...nitric acid and sulfuric acid, cold, add cellulose as cotton wool, wash, dry, boom. Then there is nitrocellulose paint, and nitrocellulose movie film...etc. Googling got me what looks like an encyclopedia of variations and uses, similar in length to, "What can water be used for?"

What is this stuff? A whole field of chemistry that started with, "boom" and now it's in my salad dressing?

You chemistry guys already make me look like I'm still poking a mud puddle with a stick, so try to dumb it down for me. OK?

 

You can add the nitrate NO3 group to many organic molecules such as starch, cellulose, glycerin or toluene. You need concentrated nitric acid and sulfuric acid is used to absorb the water that is a byproduct. This keeps the acid concentration high and helps drive the reaction forward.

Attaching the nitrate group to the fuel molecule puts the oxidant in the closest possible proximity to the fuel. With just a bit of ignition, the nitrate breaks down and releases oxygen, which in turn reacts with the fuel. Boom. The burn rate depends on the degree of nitration, particle size and so on.

Ping pong balls used to be nitrocellulose and maybe they still are. I once hit one onto a lamp where it rested on the bulb. What a surprise! It's totally the best thing to do with cracked ping pong balls, to burn them.

A low level of nitration has a minimal effect on burn rate but may have a big effect on other properties such as solubility, emulsification, cross linking and more.

 

That's a good start. I understand the nitrate connection as the oxidizer. It's almost the same as good old gunpowder except in nitrocellulose the nitrate isn't a mixture, it's part of the molecule. Now, how does this evolve into paint on a guitar, movie film, and other things that aren't supposed to explode?

For part III we'll talk about why this stuff is in food. Humans don't digest cellulose and they intentionally discard/excrete nitrates.

 

Ammonium nitrate makes an interesting explosive.
It has nitrogen on both ends of its formula.

 

Ammonium nitrate makes an interesting explosive.
It has nitrogen on both ends of its formula.

Yebbut, this is not about explosives, it's about nitrocellulose and how it evolved from being just an explosive to everything from ping-pong balls to salad dressing.

 

Ever notice "modified starch" on a food label? They make all sorts of modifications to both starch and cellulose to manipulate the chemical and physical properties of these useful polymers. Nitration is one of those modifications. If it's in food, I'm pretty sure the degree of modification is far less than you'd find in a ping pong ball or filmstrip, which in turn are less nitrated than an explosive.

You might say it's a coincidence that a chemical trick to modify the properties of a polymer, if taken to an extreme, produces an explosive.

 

OK. That's a good clue for me. I'm guessing there is a very large range of, "how much is it nitrated?".
Then the idea that nitrocellulose is not water soluble, so ping-pong balls and movie film are also not water soluble.
So, that guitar paint in the 1950's...was that lightly nitrated nitrocellulose in a solvent? Kind of like today's Plasti-coat pretend paints?

Still sneaking up on why anybody would feed humans nitrocellulose and call it, "modified" real food (starch).

 

Yebbut, this is not about explosives, it's about nitrocellulose and how it evolved from being just an explosive to everything from ping-pong balls to salad dressing.

Then I apologize for my inappropriate segue.

 

Then I apologize for my inappropriate segue.

Just glad you didn't take offense.
I learned about nitrates and oxidizers as a teen, making stuff that would get me to Guantanamo in today's world. Nitrates are not the real question here. This is about how ubiquitous nitrocellulose is, including why it is not an explosive in my toothpaste tube.

 

Here's a specific question. It seems to me that cellulose is not soluble in any ordinary way. You can put cotton anywhere except a fire, and it will still be a solid. So...nitrating it creates a soluble substance? Then it can be used as paint, dried as a film and used to make movies? Is a lot of this about how to make a very common substance soluble? In order to manipulate its physical properties?

 

Is a lot of this about how to make a very common substance soluble? In order to manipulate its physical properties?

Plain nitrocellulose is a solid which is insoluble in water.
According the Wikipedia it is soluble in this manner: Nitrocellulose is soluble in a mixture of alcohol and ether until nitrogen concentration exceeds 12%. Soluble nitrocellulose, or a solution thereof, is sometimes called collodion.

 

You've almost certainly already read this, but if not it has some interesting tidbits that might be of interest to your query.

https://en.wikipedia.org/wiki/Nitrocellulose

 

You've almost certainly already read this, but if not it has some interesting tidbits that might be of interest to your query.

https://en.wikipedia.org/wiki/Nitrocellulose

That article makes a lot more sense to me now that wayneh has given me some clues about the manufacturing process and how a chemist thinks. Neither of them clear up the whole mess, but the two viewpoints allow me to understand both of them better than I did last week.

 

Here's a specific question. It seems to me that cellulose is not soluble in any ordinary way.

Now we're getting off into the weeds. Many polymers such as starch and cellulose have one name that covers a broad range of molecules. Like linear snake versus branched tumbleweed. Both called starch.

Both the chain length and degree of branching can vary a LOT between two molecules with the same name. So there can be a subset of cellulose molecules that are indeed soluble. For instance there is also such a thing as soluble dietary fiber.

Methyl cellulose is yet another derivatized cellulose. It's soluble and widely used in food as a thickener.

 

I always thought that nitrocellulose was originally developed as a form of plastic, to mold into things. And then was found to be explosive at higher nitrogen content.

 

Now we're getting off into the weeds. Many polymers such as starch and cellulose have one name that covers a broad range of molecules. Like linear snake versus branched tumbleweed. Both called starch.

Both the chain length and degree of branching can vary a LOT between two molecules with the same name.

Well, shame on you for not having enough names.

OK. That herds me back into the corral, but it seems to confirm my suspicion that chemical "engineering" spends half its time knowing what to expect and the other half measuring substances to find out what happened. That doesn't happen in electronics. There is no way I make a mistake assembling a voltage regulator and find I have stumbled on to the next Moog Synthesizer module.

 

I always thought that nitrocellulose was originally developed as a form of plastic, to mold into things. And then was found to be explosive at higher nitrogen content.

That seems plausible. Is it true?

 

I always thought that nitrocellulose was originally developed as a form of plastic, to mold into things. And then was found to be explosive at higher nitrogen content.

Gun cotton (highly nitrated nitrocellulose) was discovered in 1832 and went into initial industrial production in 1846 (but was halted after bad things happened). Partially nitrated nitrocellulose as the first man-made plastic material was developed in 1862.

 

Well, shame on you for not having enough names.

OK. That herds me back into the corral, but it seems to confirm my suspicion that chemical "engineering" spends half its time knowing what to expect and the other half measuring substances to find out what happened. That doesn't happen in electronics. There is no way I make a mistake assembling a voltage regulator and find I have stumbled on to the next Moog Synthesizer module.

But in basic electronics and physics research a lot of things have been discovered by making something and seeing what happens. For a long time it was believed that the key to getting higher critical current densities in superconductors was to make them really, really pure. But, by accident, it was discovered that impurities were actually the key and it took a long time for researchers to figure out why. During that time a lot of conductors were just thrown together and tried to see what happened. Even today in the search for higher critical temperatures a lot of materials (and methods to create them) are just tried on speculation. A lot of the devices that are now commonplace in integrated circuits were discovered by accident, often because their accidental appearance resulted in failures of the intended device and failure analysis discovered that the failed component might actually have useful properties of its own.

 

That sure was a conversation stopper.
Anybody want to talk about super-conductors or silicon purity?