### Chilly chemical properties

Because it's the middle of winter here in Canada, I think today is a good day to talk about refrigeration.

Just kidding. Actually it's because the ISS had to replace a piece of its refrigeration system last week, and I thought that was a good excuse to talk about refrigeration.

Most modern refrigeration involves the chemical property $$\Delta H_{vap}$$, or enthalpy (heat) of vaporization. Every substance has a heat of vaporization, and the amount of heat energy required to vaporize a substance is independent of what temperature the substance boils at. To choose a rather extreme contrast, water boils at 100C while lead boils at 1750C, but water requires 539cal/g to convert from liquid to gas while lead only needs 208cal/g, less than half that required by water. This amount of heat does not account for how much is required to get to the boiling point, and if you remember your high school chemistry, the temperature does not change with the additional heat input while it changes from liquid to gas.

The basic principle in use here is that when a substance evaporates, it draws heat energy from its surroundings (or the more familiar form: when you add heat to a substance, it will evaporate), and when a substance condenses, it releases heat energy back to its surroundings. Put an insulated barrier between these two sides of the process, and you have refrigerators, freezers, and air conditioners which get colder "inside" and warmer "outside".

### Studying long

Looks like November wasn't a great month for posting, for me. Well, I'm back, and this time with another medical term. As with the others, if a medical doctor reads this and I'm wrong about something, I would love to hear about it so I can fix it. I am writing from a non-medical person's perspective for other non-medically trained people, but I hope I'm not making any doctors cringe.

So this time it's "longitudinal study". The basic idea behind a longitudinal study is that the study follows specific people for a long time—years, or decades. These can be used to tease out things like what affects aging or why some kids develop asthma but others don't, and many more.

### Chemical telephones

The folks at UCLA have come up with a way to use cell phones to test for allergens in food. And we're not talking looking it up in a database somewhere, we're talking an actual lab test, which tests the actual piece of food in front of you.

Potentially useful if you have a life-threatening allergy, such as to peanuts, the example used in their paper.

While this does use the camera built into the phone, as a lab test, it is more than just taking a picture. Specifically, it uses a colorimetric process to measure how much allergen is in the sample.

I've used colorimeters before, and they are generally quick and handy (and portable, if you buy the portable version of the reader). However, that "generally" is important. While I've used some colorimetric kits that only take 5 minutes, I've used some that take over half an hour, and that's not counting sample preparation time.

And all of those kits require sample preparation of some sort, adding chemicals, and waiting for the reaction to finish before measuring. Most of the stuff I tested required dilution of a water sample to bring it into the testing range. The peanut test described requires the sample to be finely ground and dissolved first, and is described as taking 20 minutes, not including grinding time.

The good kits come with either pre-measured chemicals or easy quantities of liquid chemicals to measure, such as with a standard pipette or a supplied dropper, to minimize test error. The reaction of the compound of interest with the added reagents causes a colour change, which the sensor (or camera) measures. Generally, at least for the kits I've used, the darker the colour, the more of the compound of interest is present. From the paper, it looks like the peanut test turns red.

Realistically, now that the photo processing and colour measurement has been sorted out, any pre-existing colorimetric kit could be adapted for cel phone use. But then, most people who might get these things for personal use would be more interested in allergens than the stuff I have tested for at work. Most people don't care all that much how much calcium is in their water, because it isn't a health issue.

(Ok, technically this one is almost year old, but I don't restrict myself to only talking about new discoveries.)

### Food chemicals

I was tossing around the idea of doing some posts on the various food additives one sees (and which some people are frightened by, due to their long chemical names) when I ran across Science Fare's list of The Ingredients of Scientific Cooking. Some of these every cook has used (sodium bicarbonate aka baking soda; sodium chloride aka table salt; ethanol aka drinking alcohol, to name the three most instantly recognizable ones), and some are a bit more specialty (such as pectin to gel a jam - mmmmm, I remember my mom's jam) and some I didn't realize people used in home kitchens. Although in hindsight, the fact that I have seen a bag of MSG in the supermarket means that yeah, people do actually use them.

This list looks like an excellent resource, though I may branch out from it and look into some of the things used only in commercially produced food, because I am curious about some of these. Especially items such as preservatives, since without them, food (and even non-food items such as sunscreen) doesn't last very long and provides a potential base for bacteria and mould, some of it potentially harmful, to grow.

### Chopping up pollution

Normally I just post whatever interesting bit of chemistry catches my interest on a given week, but today I'm posting about something of special interest to me. It's not about my work specifically, but it is about pollution remediation—and that, in a broad sense, is what I do.

This fascinating bit of cleanup chemistry targets some of the most difficult to remove pollutants. The unsightly colour of lignin stained water coming out of a pulp mill, pharmaceuticals passing through sewage plants (page 2), pesticide and herbicide runoff from farms, parks, golf courses, and lawns, and many others. Chemical warfare agents are even on the list of targets.

### Unfamiliar noises

I had just picked up a rental car to use during a work trip, of a make and model I'd never driven before. Just as I pulled out of the parkade onto the road leaving the airport and the speedometer moved above the 10, the car shook and a made a sound that had me frantically looking in the rearview mirrors to see what piece of itself the car had just dropped on the road behind me.

Nothing. The road was clear, the car wasn't shaking or making any funny noises anymore, and was accelerating smoothly. Weird.

Just as I pulled off the airport road onto the freeway, and accelerated further, it happened a second time. This was really weird. Still nothing on the road behind me.

It was probably 5 minutes later, as I was driving around a 270 degree freeway ramp to get going the way I wanted, that I figured out what the noise and vibration was. Something not visible inside the rental car parkade, and not in my line of sight when driving the car due to keeping my line of sight on the road.

Impeccable timing on that thunder, Mother Nature.

I'm glad the funny noise wasn't a sign of anything damaged or about to fail, but I've encountered those conditions more than a few times. One reason I pay attention to them!

Quite a few months ago, I mentioned a test I thought I might run. I didn't start it at the time because it was winter and my assistants for this particular test tend to be sluggish when it's cold out. Then I forgot about it for a while.

For those who followed the link above, yes, I'm talking about that test.

Meet my lovely assistants, who will be doing the actual work of the biodegradation test! It's summer now, and they're happily eating through my kitchen scraps.

### Gold, with or without cyanide

Some things are unavoidably toxic, and some things were unavoidably toxic until a new, less toxic process was discovered. Less toxic is always a good thing. Sometimes it's less expensive in terms of direct costs such as how much the reagents cost, sometimes less expensive in terms of indirect costs, such as safety precautions and environmental protection.

Sodium hydroxide is one such; the old industrial method of making it involved mercury, which is highly toxic. The new industrial method doesn't. (There are still toxic chemicals involved, but they're not mercury.)

One thing that will hopefully one day be added to the past-tense version of unavoidably toxic is gold mining. Currently, if gold can't be panned from a streambed (placer mining) where it's present as pieces of fairly pure gold, it has to be dissolved out of the rocks, often using cyanide. A newly discovered process is being described as possibly displacing the cyanide.

### Timely prizes

Here's something fun that I feel like I should have heard about before now, what with following science news and all that.

The Center for Communicating Science has an annual challenge to (surprise!) communicate a scientific subject—in a way that an 11-year-old will understand. Which means no university level math. Obviously, my posts here are not even close to what they're looking for, since I assume at least high school chemistry, most of the time, and I like including math.

One of the two winners is a canadian PhD student in chemistry and, from the look of his videos, an all-around goof. I certainly got a few laughs out of his video, and I thought his explanation was the clearest I've ever heard.

### Anti-fizz

While in Europe on a work trip and grabbing a bite for lunch at a café, I grabbed a bottle of water on my way to pay without checking the label. Checking the label is important, because in Europe, "still" water and "sparkling" (carbonated) water are sold side by side—and I can't stand the taste of sparkling water. Halfway through eating lunch, I opened the water bottle to have a drink and it sprayed water all over my tray and my clothes.

I'd grabbed the wrong sort of water. Not only that, I'd obviously shaken it at some point.

Because I'd opened it, I couldn't return it for a bottle of still water, so I decided to de-sparkle the sparkling water, in the hopes that it would improve the taste. Fortunately, this requires no special equipment and can be done in a café, although it might draw some funny looks.

### Seeing at the surface

One of the quirks of chemistry is that we measure the bulk solution, but the reaction often happens on a surface - whether it's precipitation, dissolution, or catalysis.

While we usually calculate reaction rates based on the concentrations found in the bulk solution, in a case of a surface reaction, that's out where no reaction is happening! The equations for reaction rates empirically account for this in the constants, where the reaction rate is rolled together with the rate the reagents diffuse toward the surface to react and the rate the reaction products diffuse away from the surface and out of the way.

But in terms of designing a reaction, controlling it to get, say, the product we want instead of a byproduct if there are two possible reactions, or speeding it up or slowing it down, what happens at the surface can be key. And whether we watch or measure, knowing what happens at the surface is the first step toward changing what happens at the surface.

### Epidemiology circles back to sewage

Epidemiology, the statistical study of population health instead of a single person's health, has taken population-wide sampling to a new level—underground.

Instead of collecting data on individuals representing a subset of the population and then averaging it, the researchers let an existing piece of infrastructure do the averaging for them. This also made sure they were actually getting properly anonymized data from every single resident of the study area—because the area of study was "everybody connected to the sewer", and everybody who has one, uses the toilet.

What they were testing, specifically, was the percentage of people who took their medicine, by having the entire city collectively pee in a cup.

### Opening my eyes

I was on a work trip and sitting in the lunchroom at a client site, chatting with the operators there. It was a friendly group, and we got to know each other reasonably well in our lunchtime conversations. I and one of the locals were talking about running and race training, being both runners. Another of the operators mentioned that he occasionally ran a mile at the track, and was asking about training for a 5k race, three times farther than he had run before.

Because he and I both find running more than a mile or so on the track unutterably boring (I think he hadn't run more than a mile on the track partly because he was bored, not because he was too tired to continue) I suggested that he run on the street, through the neighbourhood where he lived, so at least the scenery was a bit different. I frequently use google maps' walking directions tool to plot out a route of the distance I want to run when I'm not in the mood for an out-and-back straight line run, especially in an unfamiliar city.

He laughed and said he couldn't do that. Because he predicted a response to him being out running along the sidewalk: "Honey, call the cops! There's a black man running!" And the rest of the group laughed, because they knew it was true.

It had never in my life occurred to me to even think that somebody might call the police on me while I was out minding my own business on a training run.

White privilege: yeah, I have it.

### Don't look under the hard hat

One morning, my co-worker picked up a hard hat off a chair in the site office trailer. This would normally have been a perfectly normal thing but on this day, there was a tarantula hiding in the cozy, dark, and air-conditioned cool place it had found overnight.

After a bit of surprised dancing, the tarantula was left alone. They're pretty mellow and not dangerous, and besides, we had to get to work outside in the hot.

A while later when we went back into the office, the tarantula was on the ceiling. With a hard hat minus its harness, we got the tarantula into the hard hat to put it outside. After, of course, my co-worker asked for a photo of himself with the tarantula.

The tarantulas, as scary as they look, weren't the scary ones in that area. It was the sort of place where you banged your boots around a few times before putting them on in the morning to make sure nothing had taken refuge inside.

I never had anything inside my boots, but one morning I did wake up to a scorpion on my pants.

### Thawing sweets

Here's a thing that I didn't even know was a thing to wonder about:

You know the sugar maple, which produces the raw material for maple syrup by dripping sap into a bucket in the spring. Well, it turns out that it's not only a case of the sugar maple's sap being particularly sweet and thus well suited for this use. The sugar maple, along with a couple of other trees, are the only ones which drip their sap out in a way that can be usefully collected, and it is also particularly sweet.

The question, or rather questions, are:

Why only a few types of tree?

Why does this only happen during spring thaw, in certain temperature conditions?

How does this happen at all?

Some mathematicians from SFU on the west coast decided to calculate this east coast phenomenon.

### Chemophobia

I've been busy lately so I haven't had time to put together any good posts. In the interim, here's some interesting reading. The first sentence describes me perfectly, but then I'm one of the group named in it as well: "It’s the number one pet peeve of just about every chemical professional I talk to: why is ‘chemical’ such a dirty word in the minds of so many people?"

Even people who have some interest in chemistry can fall prey to this. I was talking to a friend (who does have an interest in chemistry) recently and this came up, and he pulled out a few of the classics about synthesized things not being tested "enough" (even though it's been my experience that for many chemophobes there is never a level that will be "enough") using "unnatural" or "chemical" as a loose synonym for dangerous—acknowledging immediately when I pointed out that there are plenty of natural poisons, because he does know more than a little about chemistry, BUT...

It's easier to argue with strangers about this, than with friends; at least I find it so. It sucks when friends hit your pet peeves, and it's easier to walk away from strangers who do the same.

### Not chemistry

Ok, this isn't chemistry, or engineering, but I think it's pretty cool.

Archaeologists found king Richard III, for real. The location and battle wounds and twisted spine were excellent clues, but the DNA test comparing the skeleton to two people descended from his sister confirmed it.

DNA testing is chemistry-related, right? Ok, this post is chemistry related after all :-)

### Natural distillation

I was out snowshoeing with a friend not long ago, and ate some snow because I was thirsty. My friend made a comment about the "distilled water" taste of snow, and I suddenly realized something that, really, I've known all along—snow effectively is distilled water.

Water distillation involves vaporizing impure water, then condensing the water vapour back to a liquid. In the case of snow, water vapour in the air freezes directly into snowflake form, making them pure—distilled—water.

Raindrops, on the other hand, while they also condense out of the water vapour in the air, absorb other vapours into the drop. There are some things that absorb more easily than others, SO2 being one of the well known pollutant related compounds that absorbs easily into water, and which makes acid rain. It's a little harder (but not impossible) to dissolve other stuff into solids.

### Bouncing liquids

Never mind hydrophobic, how about "omniphobic"?

A new material—or rather, a new shape of an existing material—has been made that rejects nearly every liquid thrown at it, both oils and waters, both acids and bases. The material is a plastic, one with slightly lower surface energy than the famous PTFE (Teflon), so it has very little stick to it to begin with.

In order to make the liquids not only not stick but actually bounce right off, they changed the shape at a microscopic level so it wasn't a smooth flat surface, but a textured surface that was mostly air:

Posted with permission from J. Am. Chem. Soc., 2013, 135 (2), pp 578–581. Copyright 2012 American Chemical Society.

### Inspired by: bacteria

Here's another one where nature meets engineering on a microscopic scale: tiny submarines small enough to swim through your blood vessels.

The submarines I'm actually talking about won't carry people, but once built they could be made to carry small doses of medicine, and directed to swim to a specific spot in your body.

The reason this merits a mention in the "nature meets engineering" category is that down at the 10$$\mu$$m scale (which is to say, 100 of these lined up end to end would only reach 1mm long) you can't just build a tiny motor and propeller and expect to have the submarine go anywhere, because at that scale, the physics of it just doesn't work. Instead, what they looked at was how creatures that are actually that small get around.

### Folded Solar

Solar electrical is pretty exciting right now, I must say. After my previous post on some of the cool stuff coming up in photovoltaics I let it slide for a while and chased other cool news, but this new thing from late December really caught my attention.

I mean, solar panel stickers? Which you can apply to fabric or paper, bend them, and have them still work?

The researchers say that this technique isn't only good for solar panels but also possibly for electronic circuits, transistors, and even LCDs as well. Maybe you really could have a solar powered, electronically active jacket, including flexible display, one day. Imagine, a self-powered jacket that could show you a map of where you are, among other things.

They tested the solar panels to a bend radius of 7mm without any damage. I don't know if it would handle a crease (if on paper) very well, or crumpled-clothes type bends. From the paper, it doesn't look like they tested its bending abilities to failure.