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This question began due to a certain fictional monster. Where it was stated to be able to secrete explosive goo activated by its saliva, which would coat its boulder-like arms and explode when smashed against the ground (or human whichever works best).This creature has nothing to do with the question, it is however the origin.

Which led me to contact explosives and Nitroglycerin. Okay, so Nitroglycerin isn't exactly the most safe substance to transport even by modern standards but I insist that it should be Nitroglycerin (Think of the possibilities, nitroglycerin-propelled spikes and bombs).

However, what would allow a creature to produce Nitroglycerin and then store it for future use?

The biggest problem might be storing such a volatile substance, as funny as it might be to have creatures that explode when they walk it doesn't make for a feasible real creature.

I only need a biological way for a creature to store this in its body and to produce Nitroglycerin, there is no need to work out other things like how it might have evolve and additional organs that would allow its use in one form or another. It is a nice bonus of course.

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  • $\begingroup$ I find production and storage a hardly related matters. $\endgroup$ – Mołot Oct 17 '16 at 12:42
  • $\begingroup$ @Mołot Well, I want to find a way for this to work before going into its function but could you give some more explanation on why? $\endgroup$ – Skye Oct 17 '16 at 12:44
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    $\begingroup$ The only restriction here is Nitroglycerin, that's it. $\endgroup$ – Skye Oct 17 '16 at 13:24
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    $\begingroup$ Why Nitroglycerin? The original stories idea of a binary explosive is much more practical and workable. (see here en.wikipedia.org/wiki/Binary_explosive) $\endgroup$ – RBarryYoung Oct 17 '16 at 18:12
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    $\begingroup$ veeeerrrrryyy carefully $\endgroup$ – Bohemian Oct 17 '16 at 21:47
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How to make Nitroglycerin

So I actually did this with some friends in high school (with stolen supplies, right after Columbine, got suspended for weeks, fire department searched my house for explosives, etc.) and it did in fact go bang, so I can confirm that the process is not super hard, if done in beakers. In an animal, this process would be tough.

Ingredients

  • Glycerin. Present in both plant and animal fats. It’s pretty feasible for a creature to produce this.

  • Nitric Acid. Not used in biology. Very powerful oxidizing acid so you can't really let in interact with any organic molecules. Would have to be stored in some sort of pouch lined with a protective layer. Since Nitric acid etches metals too, the pouch would most likely have a silica based lining. Can be produced by bubbling nitrogen dioxide through hydrogen peroxide. Hydrogen peroxide is part of what the bombardier beetle uses for defense, so it could feasibly be produced in an organism. Nitrogen dioxide in turn would have to come from nitric oxide, which is used in the body. But that requires intermediate storage/transportation of two more toxic chemicals on top of the nitric acid.

  • Sulfuric Acid. Also not used in biology. Sulfur is common enough in biological sources, but the acid itself is also nasty stuff. I believe sulfur could be contained in a lipid (fat) container, so that might be easy. Production would involve burning elemental sulfer (inside the body!) to make highly toxic sulfur trioxide (the acid part of acid rain) which would then react (extremely exothermically) to make sulfuric acid.

No

Okay I'm going to stop there. Getting the three ingredients is really not feasible in a biological organism. If you were able to get those three, you could pretty much just mix them together a few seconds before discharge and then shoot them at someone and they would end up part exploded and part covered in horrible acids. So it would be an effective weapon, but storing all those toxic ingredients in a body isn't really compatible with Earth's carbon and water based biochemistry.

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    $\begingroup$ The sulfuric acid is optional: it acts as a catalyst, and in a biological system, it's likely to be replaced with some organic catalyst. The nitric acid is also optional: clever chemistry can let you use nitrate or nitrite salts instead, which are found in biology. The nitric acid/sulfuric acid synthesis is used industrially because it's cheap and easy. $\endgroup$ – Mark Oct 17 '16 at 20:50
  • $\begingroup$ Hey I made nitro too! But I didn't get busted :) $\endgroup$ – Bohemian Oct 17 '16 at 21:48
  • $\begingroup$ What if the creature in question isn't organic, as in not carbon based? Maybe making the creature silicon based could make it viable biochemistry speaking. It would, of course, make it harder to justify such a creature if it would be earth native. $\endgroup$ – petervaz Oct 18 '16 at 13:17
  • $\begingroup$ +1 for trying it in lab and getting suspended (also for the house search) ;) $\endgroup$ – DroidDev Oct 18 '16 at 13:32
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    $\begingroup$ It should also be noted that biology generally doesn't synthesize chemicals the way we do in chem-lab. So while our method for nitrating glycerol requires nitric acid, nature's way would probably use existing nitro groups and a series of catalysts. $\endgroup$ – Nicol Bolas Oct 18 '16 at 17:32
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Short answer: The creature would most probably not store nitroglycerin. And if it did, it wouldn't grow old.

But let's explore some possible ideas, anyway.

Because I don't want to type nitroglycerin a thousand times, I will call it "nitro" from here on.

Storing nitro

Let's first examine Nitro closer (for chemical properties, Wikipedia is usually a safe source). Nitro is highly volatile, and will go off if shaken, heated, or exposed to any kind of shock or friction. No creature could store this stuff in pure form in its body. It will not detonate from body temperature (as its auto-ignition temperature is 270°C), but it might be sufficiently agitated if the creature falls, jumps, or anything.

Nitro can be diluted down with other substances, making it safer to store. But these substances would need to be removed to "arm" it again, which I think makes this idea not feasible for our creature.

Nitro also becomes more stable if cooled down to below its freezing point (about 13°C). Now THIS could be a thing. If your creature lives in arctic areas, it could have pockets on the outside of its skin or fur, where the temperature is always quite low. When there is danger, it could "pull" these pockets back inside, where the nitro thaws, and probably detonates soon after. I could also imagine a pocket of tissue that is flooded with blood to "arm" the nitro.

Actually, a strange alien creature with long antennae-like tentacles on its back might work. The tip of the antennae might hold a little nitro, and they could arm them and smash them at their enemies, sacrificing the limb in the process.

Now, if there is ever some serious global warming, or your creature cuddles with its loved one, it will have a problem.

But don't be fooled. Nitro burns at over 5000°C, so these self-detonating devices are absolutely devastating for the creature using it. At least the limb that stored the explosive will be lost for good, even it was only a small amount of nitro.

Producing Nitro

I have spent some time trying to think of a way to biologically fabricate this substance, but I am no expert on this area, and you asked for science-based. Therefore, I decided to leave this part of the answer to other users that are more well-versed in this.

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  • $\begingroup$ As to the deadly problem for the creature itself, consider small creatures like lemmings or rats. As traditional prey of various predators, they can always use another defense mechanism, even if it's lethal to some of them. Somehow they have evolved the ability to produce nitro and concentrate it when scared or mangled. A predator chomping down on one of them would be seriously hurt or even killed - teaching them that this is dangerous prey indeed! The rest of pack would be safe or might even get dinner in exchange for their loss. $\endgroup$ – Peter S. Oct 17 '16 at 15:40
  • $\begingroup$ Nevermind, been done here: worldbuilding.stackexchange.com/questions/56945/… $\endgroup$ – Peter S. Oct 17 '16 at 15:44
  • $\begingroup$ @PeterS. don't forget boomrats and boomalopes in Rimworld $\endgroup$ – John Dvorak Oct 18 '16 at 1:04
  • $\begingroup$ @JDługosz damn, i shouldn't have learned that pesky 18th century grammar. $\endgroup$ – Andreas Heese Oct 18 '16 at 6:08
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Storing Nitroglycerin

You don't store it as straight liquid nitroglycerin. You're an animal! You need to be able to run, jump, fall, etc. without exploding body parts. So, what do you store instead of nitroglycerin?

First, let me introduce you to guncotton, aka nitrocellulose. It is chemically very similar to nitroglycerin, but a lot more stable. It was even, for a long time, the primary military explosive substance.

If you mix nitroglycerin and guncotton, you can get a double-base explosive powder. Aka, modern smokeless gunpowder.

The advantages of storing your nitroglycerin mixed with guncotton as an explosive powder should be obvious. Explosive, yes, but stable under ordinary conditions. Ignition temperature is hundreds of degrees. Can be shaken as much as you want.

Unfortunately, figuring out how to create double-base explosive powder is beyond my chemistry knowledge. If I remember tonight, I will try to google around for it, but searching "how to make gunpowder" at work seems like it might not be the best idea.

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    $\begingroup$ Technically, OP said "creature", not "animal". Maybe they would be okay with a plant? $\endgroup$ – John Dvorak Oct 18 '16 at 1:08
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I think biological systems will not make nitroglycerin in the manner used by chemists, as detailed by kingledion.

nitro

Rather, the atoms will be stuck together individually from smaller groups or modified from a similar molecule, using a series of catalysts. As Wikipedia notes, “Chemically, the substance is an organic nitrate compound”. Nitrates are naturally occurring and are processed by bacteria as an important part of the ecosystem.

So, suppose that some bacteria figures out the trick of making nitroglycerin. Then the animal will use a symbiotic colony of these. Note that bacteria are the go-to for novel metabolic reactions, and are the original source of mitochondria and chloroplasts as well. This symbiosis allows animals to digest different food sources. So, there is precedent for this concept.

Now the secreted nitroglycerin will not be stored as liquid, but will be passivated as in the manner of dynamite etc. by keeping the molecules stuck to the surface of another material. This can be used like dynamite and still fill your requirement. Or, the matrix material can be removed by another process: say it evaporates quickly once exposed to air: the animal can excrete a blob of material and then withdraw as it becomes more unstable over the next few minutes.

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  • $\begingroup$ Dynamite passivates nitroglycerine with kieselguhr. This is a form of clay. This is what Alfred Nobel famous and rich, and gave the world a relatively safe explosive (well, safer than nitroglycerine). A detonator was required to make it explode. $\endgroup$ – a4android Oct 18 '16 at 3:36
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My chemistry is nowhere near figuring out a pathway. I will say that the answer that rejected it based on the required acids not being in biology isn't enough, though—life can often use pathways that aren't practical in the chemistry lab.

As for storing it, take a look at dynamite. That's nitroglycerin that's been absorbed by something. It's much safer to handle. My understanding is that what you really need is to avoid any possibility of it sloshing around or otherwise being subject to a concentration of force, though.

If my understanding is correct this suggests a way a creature can work with it—the organ that makes it consists of a whole bunch of tiny sacks in which it is produced. Make the organ spongy and capable of regeneration. So long as you keep the density low enough a blast can't propagate even if one sack somehow comes to be detonated. To weaponize it the sacks empty into a chamber.

What to do with the boom is another matter, though. It is going to be extremely hard to use offensively. I doubt a creature can make a safe means of throwing it and if it works by striking with an explosive tip that's almost certainly going to be more energy expensive to replace than the value of its prey.

Thus the only use I see for it is defensive. In this mode I can see two options:

1) Lets look at some lizards that can sacrifice their tail to escape. Consider the boom-lizard: it has a nitro organ in its tail. The chamber it is concentrated in contains a structure to make it more sensitive, once it's been triggered a tail slap results in detonation. Unfortunately, hitting the target with its tail won't be anything like certain.

2) Instead, how about a creature with several nitro organs in its body. It has no means of releasing the nitro, though—rather, the death of the creature releases it. The chambers are designed so that they will detonate if crushed. This is akin to a poisonous creature—it doesn't save the creature but it teaches predators to leave it alone. The advantage of nitro over poison is your predator won't evolve an antitoxin.

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  • $\begingroup$ See my edit for future reference. $\endgroup$ – JDługosz Oct 18 '16 at 19:25
  • $\begingroup$ Explosive tip: see snail harpoons for a suitable structure! $\endgroup$ – JDługosz Oct 18 '16 at 19:27
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This idea is troublesome for at least four reasons:

  1. Nitroglycerine is (quite obviously) highly sensitive to shock and pressure, and explosive. Let's hope that creature never needs to jump, and never stumbles. Or gets a hiccup.

  2. The presumed purpose of said nitroglycerine would be to spit the explosive at an enemy. That's a great plan, except it will likely explode while being pressed out of the "nitro spit glands". Thus, assuming none of the Bad Things (TM) from #1 happen, the creature would almost certainly blow up its head when spitting. So, this would at best be a kind of suicide attack, much like Terry Pratchett's exploding dragons.

  3. The "normal" way of producing nitroglycerine is an exothermic reaction which, in addition to very careful mixing, requires external cooling unless you are comfortable with the container exploding right in your face. Creatures tend to be at least as warm or warmer than their surroundings (consider that the dragon-like monster you linked to, is living in a quite fiery environment).
    Admittedly, given appropriate enzymes (which can in theory make pretty much everything, why not nitroglycerine...) would allow nature to solve that issue. No stirring necessary, and the one-molecule-at-a-time catalyzed composition would be much less of an exothermal thing. Still, it would be a challenge, mildly said.

  4. Nitroglycerine is highly volatile, passes cell membranes rather well, and at the same time is highly biologically active. On mammals, its most prominent immediate effect is relaxing smooth muscle. For an average-sized human, as little as half a milligram of nitroglycerine onto a mucous membrane (say, your tongue) is enough to cause near-instant hypotonia. Twice as much will -- unless you are hypertonic -- almost certainly knock you off your feet (I actually tried that when in university, you have to be a really tough one to stay on your feet), and 10-20 milligrams will almost certainly kill you. Now let's imagine a beast with 1-2 kilograms of that stuff in its belly...

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  • $\begingroup$ So maybe it was a toxin that further evolved into an explosive! $\endgroup$ – JDługosz Oct 18 '16 at 19:29
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Here are some thoughts on how nitroglycerin might be stored in such a way that it would become activated only once outside the organism's body (changing from a dilute to a concentrated form, most easily achieved by evaporation of the solvent.)

Nitroglycerin owes its exceptional explosive power to largely to its near optimal oxygen index. The idealized explosion reaction is as follows:

$$2C_3H_5N_3O_9 \rightarrow 6CO_2 + 5N_3 + O_2$$

As you can see, there is an almost insignificant amount of free oxygen left after the explosion.

Compare this to the decomposition of ammonium nitrate for example. This is a poor explosive alone but the decomposition produces a lot of oxygen. Combining it with fuel oil to take advantage of the oxygen gives a much more potent explosive. At the other end of the scale we have TNT, which is a less potent and safer explosive than nitroglycerine because it is oxygen deficient. In the idealized explosion reaction, most of the carbon remains as unburnt soot:

$$4C_7H_5N_3O_6 \rightarrow 21C + 7CO_2 + 10H_2O + 6N_3$$

Nitroglycerine (and its lower molecular weight analogues ethylene glycol dinitrate and methyl nitrate) can be stabilized by cooling or by dilution with inert material as explained in wikipedia. They are not particularly water soluble. Nitroglycerine is absorbed into the mineral kieselguhr to form dynamite in order to make it safe.

Nitroglycerine also dissolves in organic solvents (ethanol and acetone being the two most likely from a biological point of view.) in the absence of oxygen to burn in they can be considered as "inert." As they have lower boiling points than nitroglycerine, they would tend to evaporate leaving behind the more explosive pure nitroglycerine as a residue.


EDIT

When we refer to nitroglycerin, we normally mean trinitroglycerin, in which all 3 OH groups of the glycerin molecule are replaced by nitro groups. The absence of OH groups is what reduces the solubility in water. Di (and probably mono) nitroglycerin will still be explosive (less so than trinitroglycerin) and will have a much higher solubility in water, thus eliminating the need for organic solvents, which are uncommon in living systems.

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  • $\begingroup$ Nitroglycerine explodes after falling through one centimetre. Don't shake the bottle! I wonder whether nitroglycerine will still detonate when dissolved in ethanol or acetone? Suddenly to urge to experiment has me its grip. But that way madness lies. $\endgroup$ – a4android Oct 18 '16 at 3:33
  • $\begingroup$ @a4android it all depends on concentration, A good guide is the theoretical temperature of detonation. For pure nitroglycerin this is 5000C. When cut 4:1 with a diluent of similar heat capacity, this reduces to 1000C. Such a mixture will still detonate, but is less unstable than pure nitroglycerin - think gelignite or dynamite. When cut 100:1 with a diluent it reduces to 50C, which is probably safe. As mentioned in wikipedia, nitroglycerin is used as a heart medicine in suitable formulations. $\endgroup$ – Level River St Oct 18 '16 at 5:37
  • $\begingroup$ Very interesting. Thanks for the additional information. Most enlightening. $\endgroup$ – a4android Oct 18 '16 at 6:02
  • $\begingroup$ The chemist in me is screaming at the use of non-integer quantities in your chemical formulae (you can't have $.5$ of a molecule!). Please double up the quantity of nitroglycerine and quadruple the quantity of TNT so that all of your numbers are integers. $\endgroup$ – wizzwizz4 Oct 18 '16 at 16:16
  • $\begingroup$ @wizzwizz4 you can`t have .5 of a molecule, but you can have .5 of a mole (1 mol = 6.23E23 molecules, such that 1 mol of carbon-12 weighs 12 grams.) I have degrees in chemistry and chemical engineering and expressing the decomposition per mole of reactant seems the most natural way to go (it's how the heat of composition would be expressed, for example.) I won´t edit it, but if somebody else really thinks its clearer, I won´t roll back an edit provided the formulas remain balanced. $\endgroup$ – Level River St Oct 18 '16 at 16:34

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