Tuesday, May 31, 2016

Why Frixion Pens Are the Sneakiest

This is a fun bit of everyday chemistry I discovered while studying for exams. I used these erasable Pilot brand Frixion pens. Or I should say, "erasable." Most erasers work by abrasion, meaning they wear away at the writing until it's gone. Pencils use graphite which forms in molecular sheets of carbon, so it's relatively easy to wear away a bunch of sheets at a time without having to wear away the paper. Frixion pens, on the other hand, erase using heat. When you rub the special eraser against the paper, it gets very hot, which degrades the ink, making it invisible. You can test this by briefly touching a written sample against a heat source (just don’t burn the paper!) This has interesting implications. A lot of what we perceive as color is really based on how light reflects back to us. This gets complicated, but there's a specific phenomenon called conjugation that is likely at play here. Long chains or rings of carbon atoms where double bonds alternate with single bonds form an electronic system that reflects back to us in certain ways. Look at lycopene, from tomatoes:

Each line segment represents one bond between two carbon atoms. Double bonds are two lines.

This is one substance responsible for making tomatoes red. When light hits it, the photons cause electrons to move back and forth across the double bonds of the molecule, and so some light energy is absorbed and only the red light reflects back to you. It’s a little more complicated, but that’s the basic explanation. This phenomenon is usually observed when you have extensive conjugation, which is just another way of saying: many bonded carbons that alternate between double and single bonds.

I think the pens use ink with long carbon chains or rings that have this property mixed with another substance that reacts with the ink when heated. I don’t have direct evidence for this, because I haven’t done a chemical analysis of the ink, but as soon as I realized that heat was what “erased” the ink, I came up with a working hypothesis. Now I should clarify that this could be completely inorganic for all I know. I'm not a dye chemist, so I don't even know what's likely, but there are inorganic ways of getting color as well as ways of combining organic and inorganic substances. I'm focused on conjugation here because it's a cool concept that's easy to explain.

Breaking double bonds with heat and turning them into single bonds is “turning off” the conjugation. The ink is still there, but when you heat it, it becomes clear. These sorts of reactions, where double bonds are reduced to single bonds tend to be reversible, and you reverse them with-wait for it... temperature. So I “erased” a message and stuck the piece of paper in the freezer. When I pulled it out, it was restored.

(Click to embiggen.)
This is an example of a reversible conversion where the amount of conjugation changes. This would require the presence of another substance to convert, since there is a different number of atoms in each.
I realized then that there’s another, neater way to do this. Normal visible light usually needs a fair amount of conjugation (again, that’s long chains of carbon with alternating double and single bonds) for color to be affected. When you have long chains like this, you usually can’t break down all the double bonds at once, instead you just break some of them, and create smaller regions of the molecule that have conjugation. Visible light is too low energy to be affected by this, but a higher energy light source will react very differently. Ultraviolet light will show conjugation that visible light will not. It’s probably more complicated than this. So I tried my blacklight on it.

Boom. You now have a recipe for invisible ink that you can buy at the store. You don’t need a black light, but it helps. Of course, the biggest problem is that the pens still leaves indentations that are visible. There are some simple solutions: Write in between the lines of a real message. People won’t look too closely at it.

Another solution is to write on paper that isn’t so white. Just don’t use construction paper, the paper tends to be of such low quality that when you erase the message, you actually end up rubbing it away. The best paper choice is a neon color. They turn up bright under a blacklight and give good contrast.

Have fun with it!

Thursday, July 23, 2015


I was on Facebook last night when I noticed a trending item.

(Click to embiggen.)

 The picture in question appeared to be a twitter item from @san_kaido:
The apparent translation, found at various websites is,
"The right one grew up, split into 2 stems to have 2 flowers connected to each other, having 4 stems of flower tied belt-like. The left one has 4 stems grew up to be tied to each other and it had the ring-shaped flower. The atmospheric dose is 0.5 μSv/h at 1m above the ground."

Alarming? Isn't it?


Allow me to explain why. Go to Google and type in (without quotes): "Mutated Daisies -Fukushima"

For those unfamiliar with different search query techniques, the minus sign (-) in a search will find you all results that do not include the keyword following it. This brings up an uncountable number of pages with pictures of mutant daisies. This kind of mutation is actually fairly common among daisies. Actually, mutations are incredibly common, period. In humans, the background rate of birth defects is five to ten percent. That is astonishingly high if you think about it. Of course, it counts a lot of relatively harmless birth defects. I have a congenital mitral valve regurgitation (heart murmur) that I was born with. It only causes me mild discomfort about once or twice every six months or more. You might have a birth defect you don't even know about.

What causes these defects? Well, it might be simpler to list the things that don't cause birth defects, like aliens from the planet Xlorrbnacht 2. The fact is that background radiation (radiation from the sun, various naturally occurring minerals, radioactive byproducts from burning coal), chemicals (including naturally occurring chemicals from food we eat), and various other factors combine to create a non-zero chance that a given person will be born with some kind of birth defect or another.

So how do I know that this daisy wasn't mutated by radiation leaked from Fukushima? I don't. For one thing, I'm not a plant biologist, so I don't know what kind of mutation this is. For another thing, I don't know if the overall rate of that particular mutation has increased appreciably above the background rate. I only see one plant. What I do know is that the person who took the photo mentioned that the radiation in the area was 0.5 μSv/h. That's possibly lower than the radiation dose I'm receiving as I type this here in the Midwestern United States, because I'm sitting in a basement in an area rich in limestone. Could the plant have mutated due solely to normal background radiation? Yes. You or I could too. That's where a lot of cancers and birth defects come from. But I strongly doubt it has anything whatsoever to do with the disaster at Fukushima.

The major media outlets haven't yet picked up on this photo, and I really hope they don't, at least not without a competent scientist on hand to explain what people are actually looking at. But, you don't really need one. All you really need to evaluate this photo is Google and a minus sign.

Thursday, February 26, 2015

Poisoning the Well With Antifreeze

Photo by Sealle, used under CC BY 2.0 license.
 There is a rhetorical practice called poisoning the well. It involves telling people that they shouldn't pay attention to an argument, before it's made, because the person making it is somehow a horrible person. We do this by saying, "Don't listen to that guy! He's a Democrat!" or "Don't listen to her! She's a conservative!" We've all done it at some point, and worse still, we've all fallen victim to it at some point. The reason it's problematic is that who a person is, what they do, even whether they're a terrible human being, doesn't stop them from being right about certain things. A fascist can give you the correct time, a liberal can tell you the sky is blue, and a child can tell you that E=mc^2.

There is a much subtler form of this that can be done with inanimate objects. "Don't put sulfur mustard in your body! It's a chemical weapon!" Sulfur mustard is indeed a chemical weapon. Of course, sulfur mustard is also an early chemotherapy drug which worked precisely because it is a cellular poison. So the advice to categorically refuse to put it in your body under any circumstance is somewhat misguided (now we have some better drugs- though I'm no oncologist). This brings me to the interesting case of antifreeze. I recently read a story about dog owners suing Purina, the pet food manufacturer, alleging in part that the practice of adding propylene glycol to dog food killed their dogs. The article correctly states that propylene glycol is a component in antifreeze. This is where I tell you, in no uncertain terms, that antifreeze has an unfair reputation. Sorta. Kinda. It's a long story, so let's get to it.

What's In a Name?
What's in a name? that which we call a rose 
By any other name would smell as sweet;
-William Shakespeare. Romeo and Juliet, Act II, SceneII.
A few days ago I wrote about the Food Babe, and she has made much about the presence of propylene glycol in certain foods. She states that it is a component of antifreeze, and that we should be very afraid. As others have pointed out however, propylene glycol (which is in antifreeze, I'll get to this in a second) is distinct, and completely different from propylene glycol alginate which is what is actually in the foods she's highlighting. You see, in chemistry, these seemingly small differences in words are absolutely devastatingly critical. The International Union of Pure and Applied Chemistry (IUPAC) is in charge of coming up with the international standards for naming chemical compounds, and because chemicals are so diverse, the naming rules can get incredibly complicated. What you need to know is that just because chemicals sound similar, or even rhyme, it doesn't even mean that they are at all related.

Take bromine, for example. It's a toxic gas. Theobromine is an important component of chocolate. So it should be similar, or at least have some bromine in it, right? No. Theobromine is named after the scientific name for the cocoa plant, Theobroma cacao in which it was first discovered. There is absolutely no relationship to bromine, the element. In fact, it's much more closely related to caffeine.

This brings us to alginates. Alginates are actually derived from kelp, they're gel-like sugary substances. They're useful for many, many things. Since they're derived from kelp and seaweed, which we've been eating for centuries, we don't mind putting them in food. So propylene gylcol is not the same as propylene glycol alginate. They're just not the same.

Even when compounds are similar, it doesn't mean that they're not radically different in the effect they will have on the human body. A similar naming story is methanol and alcohol. If you take fruits and certain vegetables, and allow them to ferment, they produce a bitter, combustible substance we know as alcohol. The chemical name for alcohol is ethanol or ethyl alcohol. If you're desperate enough for alcohol that you decide to hack apart your furniture and ferment the wood, what you'll get is a related compound once known as wood alcohol, an better known to chemists as methanol or methyl alcohol. The names, and even the structures, of ethanol and methanol are incredibly similar.

The effects could not be more different. Alcohol will intoxicate you. It's so good at this we sell it by the bottle in various flavors. It's poisonous, of course, so we tell you that you should be careful not to drink too much, but a lot of people risk it anyway. Methanol is also poisonous, but if you drink a glass of methanol, you won't just be intoxicated, but blinded. Methanol breaks down in the body to form highly toxic compounds. Homeless alcoholics, finding themselves without money to purchase quality alcohol have succumbed to the effects of ingesting methanol, since its effects are initially similar and it smells similar. It's also generally not taxable, which makes it cheap. Whether you drink alcohol is your business, but you should never, under any circumstances, drink methanol as a substitute.

In chemistry, a rose by any other word might kill you.

Bait and Switch.

One of the main components of antifreeze has long been the sickly sweet, and absolutely toxic compound ethylene glycol. Ethylene glycol is toxic to humans but the "glycol" in its name is actually a hint that it's in a class of compounds known as diols. Its sweetness has lead to it being used as a poison of choice by various cruel individuals. So that's it then? Case closed. Antifreeze is bad for you and anyone who puts it in food is a bad person, right?

Not exactly. Precisely because ethylene glycol is so toxic, and because it's bad for the environment, there has been a move to use a related compound in antifreeze: Propylene glycol. The idea is that it will keep your car running, but if leaks, it won't be as bad for plants and animals. Remember the difference between alcohol and ethanol? There's a similar one here. If you've eaten ice cream in the past ten years, chances are you've ingested some propylene glycol. In fact, the FDA has stated the propylene glycol, in small amounts, is safe. When you ingest it, your body breaks it down into lactic acid, which your body knows how to deal with since it makes lactic acid every time you exercise.

The problem is that even though the toxicity of a lot of brands of antifreeze has gone down, people are still behaving as if having the same product as a food additive is a monstrosity, even though the only reason it's in antifreeze is precisely because it's less toxic. You can't win for losing, sometimes. Antifreeze was (and still is) highly toxic, so we've make it less toxic by using something that could be considered a food additive, and the response has been to look at food and go, "There's antifreeze in there!" If we somehow figured out how to clear clogged drains with coffee, then people would turn around and go, "Did you know that they sell coffee with drain cleaner in it?!"

Of course, antifreeze still has a bunch of other toxic compounds in it, including methanol, so it should go without saying that you shouldn't drink it.

Hair of the Dog

Here's the thing about the news story: It doesn't smell right. I don't know anything about the toxicity of various substances in dogs, but the plaintiffs' cases sound a lot like attribution error, where people pick seemingly linked events and tie them together. These days, you put up a Facebook post saying dog food killed your pet, and everyone whose dog dies of similar symptoms checks to see if they have the same dog food. If they don't, they don't say anything. If they do, they become another data point that seems to confirm a trend. I don't think that Purina actually does very much different from its competitors, and if propylene glycol kills dogs, then why only Purina dog food? There are cheaper, far more corner-cutting brands out there that no one is accusing of anything.

I'm not saying that Purina is in the clear, and that I know for certain that their food has always been safe. I'm not even saying that propylene glycol is probably okay for dogs. I am pointing out that claiming it contains "an antifreeze chemical" is a lawyer's gambit, not a scientific evaluation of how harmful it is. If you've ever drank tea, no matter how pure and natural, you've ingested large quantities of a chemical commonly used in sewage treatment: Water. See how ridiculously easy it is?

Losing a pet is tragic, and I have sympathy for the owners who have lost pets. I have pets of my own. Still, it's important to analyze a news story critically, and look at what is being said by who. Nothing against lawyers, but lawyers are not paid to make scientifically accurate statements, and neither are their very-coached clients.  It is also incredibly useful to think generally in these situations. Are other manufacturers probably doing the same thing? Why only Purina brand? What could they be doing different? Why deny it? (This one isn't as obvious as it seems.) Who are the lawyers? Who are the plaintiffs?

The conclusion you reach may be different from mine, and I don't think that would be entirely unreasonable- just don't base it purely on the fact that propylene glycol happens to be in antifreeze.

Monday, February 23, 2015

Holy Mother of Clickbait

I read Mother Jones sometimes. Oh hell, full disclosure: I subscribe to the print version, but I'm increasingly annoyed by their choice of words to entice people to read articles from Facebook. Sometimes, it's borderline irresponsible, but others... well, it's just downright irresponsible.

This is what I saw on Facebook earlier:

What the actual fuck, MJ? Acidification is not "terrifying." Well, yes it is... sorta.

This is precisely why this headline is problematic, it's not inaccurate, but it is sensationalist. The actual article is reasonable reporting on a real issue, with a much more responsible headline:

What? I thought we were talking about oceans of flesh-melting acids? Obviously too much acidity or basicity in an aquatic environment will kill aquatic life. I don't deny this, and plan to write about it myself. The Facebook clickbait, however, was over the line for a responsible new organization. Again, it's not that what they described should be below our concern, but using the horror-movie properties of acids to spur pageviews is over the line. Mother Jones needs to stop using cheesy social network marketing tactics if it wants to continue being considered a responsible news organization.

Babe in the Woods

100% Chemicals. I can guarantee it.
"There is just no acceptable level of any chemical to ingest, ever." -Vani Hari, in The Atlantic.

Statements like this invariably make me cringe. Of course, everything that is a thing, is a chemical. Not ingesting chemicals is essentially advice to starve yourself to death. Vani Hari, the progenitor of this pronouncement, styles herself as the "The Food Babe." Thing is, She using classic sensationalist tactics to gather pageviews, a practice that infurtiates me.

For the past month, at least, I've been working on a series of posts about artificial sweeteners. This process has me reading several books, multiple published peer-reviewed studies, and generally has me sweating every detail to ensure that I'm delivering accurate information. If you read my Policies, you'll see I'm not a research chemist or someone who works in the industry. None of this is my forte, so I have to work extra hard to generate a short, relate-able post with good information in it.

None of this is a complaint. I enjoy doing the legwork and research. I love learning new things about sub-fields of chemistry. What concerns me is that  the economies are drastically different. Hari can dash off a Googled-together link soup of highly dubious claims, throw a clickbait headline in the there, and pump it through context sensitive advertisers in what? Ten minutes? An hour? Professional Journalists working on a "short" piece about biotechnology have to verify sources, interview people, throw out bad information, and ultimately come to a responsible conclusion. A scientist studying one small aspect of biotechnology has to go even further, study the issue longer, and is subjected to more paperwork than anything Hari ever encounters writing an irresponsible blog post about some harmless chemical or another.

This economy of effort strongly favors Hari's type of messaging. I don't have her time, her funds, or her following to make a dent in the nonsense she's spewing. Fortunately there are others helping to fight back.

Look, I'm sympathetic to the idea that not everything that can be put into food should be put into food. However, when you look at how we live today, we're far healthier than at any other period in human history. We can't very well live forever, and I accept that no matter how well I eat or how much I exercise, I'll eventually die. So I don't understand these claims of how we're being gradually and slowly poisoned. They make no sense in the modern context of people being fairly long-lived.

I could do a series of posts on why Hari gets everything wrong, but it would take up an unbelievable amount of time. Proving negatives is difficult when it's not impossible, and I'd have to put a lot of effort into making sure I'm being accurate. The fact is that a well-informed society needs something more than science bloggers typing away angrily at their computers to combat this kind of fuzzyheaded fearmongering. It needs people to be more skeptical of claims, and to look hard at where they come from. Who do you believe? Someone who has spent decades in a field doing the work saying, "Probably...", or someone with a finance degree saying, "Definitely!"

"Probably" is a lot less satisfying, I know, but it has a higher chance of being correct. A popular quote attributed to Bertrand Russell goes,
"The fundamental cause of trouble in the world today is that the stupid are cocksure while the intelligent are full of doubt."
With anything involving the human body, we're looking at highly complicated, highly variable systems that are evaluated using a very complicated set of statistical metrics that ultimately spit out percentages. Absolute certainty is elusive, and hard to pin down. So here's my rule for people who are concerned about foods and additives: Unless your doctor says otherwise, and the FDA approved it, it's probably fine.

It's not certainly fine. Your doctor could be an idiot, or the FDA might have missed something, but between the two of them, there is a lot more knowledge of biology, chemistry, and biotechnology than you probably understand. It's not that you're stupid or incapable, it's just not what you do. I don't spend a lot of time telling accountants that the way they do things has slowly been bleeding their company dry of money for years, because it's not my field. I haven't put in the time to understand it. I can do math, but it's not the same. In fact, just saying, "I can do math," belittles the practice. It would be like saying I could do a better job taking care of your kids because I've babysat before.

I encourage people to use the scientific knowledge they gained in high school and from books in their daily lives, but it's important to understand the limits of your knowledge. Time and time again, I've learned this lesson the hard way. Vani Hari will tell you that you don't need an advanced degree to understand biotech and chemistry.  I both agree and disagree.  You may not need an advanced degree to understand it, but you certainly want to be getting your information from people who can check your conclusions for accuracy.

Science, as a profession, whether it's practiced by academics, engineers, medical specialists, or privately employed scientists has gotten too big for everyone to be in cahoots, and consensus should not be confused with collusion. Does the hand of industry reach out often to pull science in one direction or another? Absolutely, but it's nowhere near being the closed ranks of a cabal of greedy people that Hari makes it out to be. Especially because there is so little money in science. Sure, companies like Monsanto, Dow, DuPont and others can make out like bandits. The simple fact is that employment is a function of supply and demand, and universities are increasingly churning out students with graduate degrees in the sciences because they're seen as a sort of "sure thing." Nothing could be further from the truth.

However, if you are tempted to follow the Food Babe down the path she's leading you, let me point something out to you. The Food Babe is eventually just going to be replaced by the Food Guru, or the Foodinator, or the Food Fluff-Patrol. These people don't last, they're fast flying, fast-talking fads. They're inevitably replaced by the next irresponsible gimmick. Where does that leave us, the people advocating responsible reporting and understanding of science? We'll still be here, hacking away at our laptops, telling you to think critically. Minus the million-dollar book deals.

Friday, February 20, 2015

Wrecking Crew

After wrangling with my settings for about 30 minutes to make sure that comments could be accepted for my latest post, I've realized that parts of this site are still rusty. Over the next week, you can expect a lot of changes to the blog. Please be patient, it isn't easy coming back from the dead.

Dropping Acid

Growing up, I believed there was real magic in the world. I'm not talking about believing in ghosts, ghouls, sorcery, or secret words that unlocked doors; I knew magic was real because acids were real. In my imagination, they could eat through anything. When other kids transformed the living room floor into lava as an excuse to jump from one piece of furniture to the next, I always turned it into acid. Sometime I'd turn it into acid-lava, if a friend was over, as a concession.

Before you pin my love of acid on the chemistry-obsessed geek I would grow up to become, I have to point out that I wasn't the first or the last person to be enamored of this mysterious class of chemical. According to Hollywood, at least, acids are still magic. As chemistry blogger Deborah Blum pointed out in her blog, Skyfall was a relatively recent example of Hollywood casting acid, as it typically does, in a villainous role

Hollywood and Hydrogen, Donors and Dollars

Another example that sticks in my mind is a scene in the 1999 film The Mummy, where a gaggle of workers opening a tomb are horrendously melted by "pressurized salt acid." This got a laugh out of me in the theater. Salt acid is most likely a reference to hydrochloric acid, HCl in chemical shorthand. HCl isn't that dangerous. There's a caveat here, obviously. I'm not saying that you should run out and jump into a swimming pool full of it. It is dangerous. When I say it's not that dangerous, meaning it's not as dangerous as it is made out to be in The Mummy. Concentrated hydrochloric acid in the eyes will probably blind you if you don't have access to water and healthcare. But just getting some on your skin won't melt it off instantaneously.

Acids are really just a peculiar class of generous chemicals that under certain conditions, want to give you a hydrogen ion- a proton. That's it. Beyond that, acids are extremely varied.  In fact, it's a little unfair to lump them all together. It's a little like taking every person in the United States who is willing to donate a dollar to charity, and saying, "All these people are the same." Especially when you consider that a lot of those people may be willing to donate a dollar only to specific charities, or that people who normally wouldn't donate anything would if the cause was powerful enough.

Acids are acidic relative to things that less acidic. Whether something wants to give a proton is measured just as much by how badly the other substance it interacts with wants to take a proton. This makes perfect sense if you think about it: How do you measure how reactive something is, unless you know what it's supposed to react with? Going back to the charity analogy, how do you know how willing you are to donate a dollar, unless you know to whom you're donating that dollar?

In fact, isn't everyone with a dollar a potential dollar-donor? If you're guessing that means that anything that has a hydrogen atom in it can be a potential acid, you're on the right track. If you're really astute, you've already thought about it and realized that water has hydrogen, so could it be an acid? Go back up to the last paragraph, "Acids are acidic relative to things that are less acidic." So the answer is yes, water is acidic, compared to something like sodium hydroxide, which much less acidic than water. In fact, we use water as a baseline for acidity, and say that anything less acidic than water is a base, and anything more acidic is an acid. What are bases? How are they related to acids? I want to cover that in its own post. For now, just know that acidity hints at something much larger in chemistry: Reactivity.

I realize that by explaining how acids work, and how just about anything with a hydrogen atom on it can be acidic, I've taken away a little of the magic. While knocking it off the list of universally sexy, Brendan Fraser-endangering substances, acids are still quite fascinating and dangerous in their own way. So let's put some real magic back in.

Working In the Lab, Late One Night

Here I steal an anecdote directly from my high school biology teacher. When she was in grad school, she was working in a lab with someone who regularly left behind a mess in the lab and never cleaned up after herself. My biology teacher took it upon herself to clean up after this person. Maybe it's because she was more of a biologist than a chemist, but she had a lapse in judgement. She picked up a large glass bottle with what, from her description, sounded like about 500 mL of concentrated sulfuric acid sloshing around the bottom of it. She decided to get rid of it, and to dilute it first. She put it under the faucet, poured a fair amount of water into it, capped it, and proceeded to shake it around a little. The chemists reading this are now sitting up in their chairs with interest. She said she shook it once, twice, and before she could bring the bottle down for a third shake, it exploded.

Glass was everywhere, she was bleeding from some cuts, and she was frozen, staring at the remnants of the bottle in her hand and thinking, "Oh, right... exothermic."

If you want to try your own experiment at home. Here's one you can try. Don't worry, nothing will explode disastrously. At worst, you'll make a slight mess in your kitchen.

1. Get a Styrofoam cup, with a lid.
2. Get a reasonably accurate lab thermometer (they're on the internet, they're cheap, and most don't contain mercury.)
3. Get some room temperature water.
4. Get some room temperature white vinegar from the grocery store (it's an acid).

Fill the cup about halfway with water and stick the thermometer through the lid of the Styrofoam cup- or calorimeter (because that's what you've just built.) Check the temperature. The water should be close to the temperature of the room, if it's been sitting out for a bit. Check the temperature of the vinegar, then pour some vinegar in the water. I'm not going to say in what amounts. It's science: Experiment. See what you find.

I think you'll see that the temperature of the water will change. Isn't it odd that two substances of the same temperature will spontaneously heat up?

Got baking soda? Go ahead. Play around with that, just remember that baking soda and vinegar tend to foam up and make a mess. I'm not in the business of telling you what to do. Just don't be stupid and pour vinegar in your eyes, or step on the thermometer with your bare feet. I also don't recommend trying to extend this experiment beyond vinegar and baking soda if you don't know what you're doing. The advice I have for any experimenter, young or old? Buy a notebook, keep meticulous records, and erase nothing. If you make a mistake, cross it out so it's still legible. You never know when a mistake will prove valuable. Want to do some fun, safe, controlled, lab experiments at home? Buy this book.

Skulls and Crossbones

Still, I understand, you're reading this in the hope that I'm going to write something unexpected, something cool and sexy about acids. You yearn for me to tell you there's an acid out there that will do this (warning, even if you know it's just latex, it's still pretty gory.) I understand. There's something deep and dark and fascinating about a killer. Acids can be of course, dangerous and corrosive and worth being careful around for many reasons.

Strong acids will both burn you and not burn you. It's a little confusing, because highly concentrated acids will react with water in your body to release heat. This creates a thermal burn. But, what most people describe as a chemical burn, is really just chemical cellular poisoning. Strong acids will denature, or warp the proteins that are the building blocks of your cells. Either they destroy them or they twist them out of shape so that they no longer function. They will directly destroy cell membranes, essentially popping your cells open. Then, there's hydrofluoric acid.

If you want to think of acids as Hollywood villains, there are the henchmen, like hydrochloric acid, which is harmful- but you do carry around a bunch of it in your stomach. It gets used a lot in high school chemistry labs. A friend in high school got some in his eye (he wasn't wearing goggles- an unwise choice on his part) and had to wear an eye-patch for a week, but he recovered. Sulfuric acid can be pretty nasty. It's often employed by the scum of the earth to attack women in certain parts of the world. But these acids are just strong. They're burly and macho and shove things around. If you want scary, if you want a serial killer, hydrofluoric acid (HF), is one of those. HF has an acidity about one hundred times that of vinegar, but that actually means it's fairly weak. Stomach acid is about ten billion times more acidic than HF (literally, I don't just throw the word billion in there for hyperbole). Sulfuric acid is even stronger. Yet an experienced chemist, Hylton Jolliffe, had this to to say about it on his blog,
 "Actually, it's just barely a gas. In a cool room it'll condense out as a liquid (it boils at about 20 degrees C, which is 68 F.) The straight liquid must really be a treat, but I've never seen it in that form, and would only wish to through binoculars."
This is because the fluoride part of HF will wreak havoc on your body's biological processes. It is a protoplasmic poison-- a cell murderer, and it wreaks havoc with your body's electrical impulse system by binding to calcium, and never letting go. The worst part? Initial exposure can be painless. Victims will not realize they've been poisoned until hours after exposure, after damage is well underway. By then, Calcium fluoride crystals have solidified in their bodies, causing intense pain, and fluoride is invading the bones, stealing calcium, all while interfering with muscular function, including your heart function. Like any hazardous chemical, sulfuric acid demands respect. Hydrofluoric acid demands fear.

Avast! Ye Rum-Soaked Scurvy Dogs!

Of course, knowing that vinegar is an acid is a good hint that acids are not all so deadly. As I mentioned above, acids are as varied as people. You need ascorbic acid, for instance, to survive. Ascorbic acid is better known as Vitamin C, and unlike other certain other vitamins, we cannot make our own vitamin C, or store it. We lost that ability with our primate brethren. if you go back far enough, our ancestors likely synthesized it in their bodies. However, primates naturally have diets sufficiently high in Vitamin C, and so as they evolved, a mutation occurred somewhere along the line that meant we lost that ability. This is an example of evolution "running backwards" or rather, of the fact that evolution is not some neat, linear process. Early primates that couldn't create Vitamin C in their bodies weren't adversely affected by the mutation, at least not seriously enough to die off before they could reproduce.

Much later in history, as humans evolved and began undertaking lengthy sea voyages, this mutation came back to hurt us in the form of scurvy. The "vita" in vitamins is the Latin word for life. We require these substances to survive. Scurvy killed sailors in the early modern era (circa 1500 CE) and when citrus was discovered to ward off the effects (at the time, it was not known that ascorbic acid was the reason) it became a closely guarded military secret, since it allowed navies to extend their voyages.

Other beneficial acids? Well, I don't exactly know about beneficial, but anyone who has ever uncorked a wine bottle or mixed a bloody Mary has encountered the intoxicating effect of a weak base known to most people as alcohol. Relative to the alcohol, you are very slightly acidic.This popular and mildly addictive drug has affects your nervous system in many different ways, and there is no one effect caused by alcohol. The high you experience from alcohol isn't solely due to its interplay with your acidic properties, but these properties do play a role play a role. Actually, the acidity of alcohol and water is nearly the same. And sometimes alcohol will play the role of acid or base, depending on what it's doing in your body. This property, or acting both as acid and as base, is known as being amphoteric, and it's not all that uncommon.

There is so much more to the world of acids and bases than can be contained in a blog post. Acids are not so much interesting as a class of chemicals, as they are a reminder that the chemical universe is vast and varied. Their properties are not limited to a single number, like pH (yet another post). They kill and they save, and the dangers they sometimes present serve as a reminder that nature is can be quite the savage beast. They can get you high and they can cut you down. The central theme, the big lesson, is that a lesson in acids is a lesson that gets at the root of what chemistry is: What reacts with this? Why? How? Why do things with similar properties in one respect (the acidity of water and alcohol) behave so differently in other respects (one hydrates and the other dehydrates)? This story is the entire story of chemistry. Once you start to pull at the threads that will answer these questions, you find that the stories get a lot more complicated, and a lot more interesting.