Vitamin C makes you not dead

I'm sure you've all heard the story of how vitamin C either prevents or cures the common cold. Some of you may also remember that vitamin C prevents or cures scurvy. But what exactly does it do for our bodies? I decided to do a bit of searching and find out.

Clues to what vitamin C does for us can be found in the symptoms of vitamin C deficiency itself. Scurvy is not just the disease where your teeth fall out, though that is one of the symptoms. Bleeding gums, bleeding under the skin (bruising), bleeding in the joints (joint pain), bleeding at hair follicles, and bleeding at previously healed scars start off the list of visible symptoms. Before those is fatigue; after those is death.

All of those bleeding symptoms demonstrate that the body is falling apart and can't keep its blood inside anymore. Quite literally: vitamin C is required for the production of collagen, the structural support cables of our body. They're found basically everywhere, including in bones and teeth, where they're mixed with minerals. Lose the ability to make new cables, and you lose the ability to repair routine damage day to day - and over time you lose the microscale structural integrity that keeps the blood inside your veins, among other things.

Fatigue is so general a symptom it can't really be used to diagnose anything. Besides, you probably just stayed up too late. But even here, it seems that vitamin C plays a role. In addition to being crucial to making collagen, it's also crucial to making dopamine, norepinephrine and epinephrine (adrenaline), and carnitine.

Carnitine is an escort for fatty acids into the mitochondria, according to the link above. Basically it's the fuel injection system for the motors that power our cells. While we get most of our carnitine from our diets, particularly from meat, if we're so low on vitamin C we're suffering from scurvy, we probably have low carnitine intake as well, a double-whammy.

But carnitine is in meat, and vitamin C is in oranges and other tasty veggies and fruits, right? How could the inuit survive on a meat-only diet? Actually, there's vitamin C in meat, too: mostly in organ meat, and the inuit do just fine without vegetables, on their traditional diet.

In fact, it looks like just by eating a reasonably healthy mix of food, you'll get enough vitamin C. Not everybody manages this, but I guess scurvy is rare enough now that people forget about the whole "it keeps you alive" part and instead spend their time thinking about some of its very minor effects.

As for curing the common cold? survey says… taking it when cold symptoms appear does no better than a placebo; taking it every day reduces cold duration by maybe 10%; and if you're physically stressed (i.e., working in a cold climate or running marathons, not just worried) then taking it every day can be justified because it gives significantly more than a 10% benefit.

Saturated gas masks are worse than useless

Activated carbon is a pretty amazing material. It's just carbon, the same stuff as in charcoal, diamond, and the carbon black that shows up on the bottom of pans and kettles used over flame, for those who have gas stoves or enjoy camping. At the same time, it's an incredibly important material for purification, because one of the neat things that activated carbon does is trap toxic stuff by adsorption. It doesn't catch everything, but it catches so many different things that it's often used in gas masks when you don't know what toxic gas you might encounter - for a HazMat team, for example, those who aren't using SCBA tanks.

One unfortunate problem with any filtration system is that the filter itself has a limit to how much crap it can capture from the water or air that's passing through - and the filter can't tell you when it's getting full. How do you know when it's time to change your Brita filter? How does a HazMat team know when their gas masks stop working? In a plant situation with large equipment, you can install sensors to monitor for breakthrough, but that's not practical, and sometimes not even possible, on small portable filtration systems.

A team from the University of California San Diego recently published in the journal Advanced Materials a paper on the production of carbon nanofiber photonic crystals. These are a special crystal form of carbon which, once they've captured toxins, change colour. No power required, no special equipment required, no extra weight for HazMat to carry. These crystals can be embedded right in the activated carbon filter, so they see exactly the same level of toxin as the filter itself. If you embed them at varying depths in the filter, you could actually watch the adsorption front as it moved through the filter, and know with certainty when your filter is getting close to breakthrough, and thus when it needs to be changed.

Up, up, a little bit higher

In honour of today's shuttle launch, I thought I'd start off with a bang, or at least a roar of fire: rocket fuel!

The shuttle uses two different styles of rockets with two very different types of fuel: liquid and solid. The shuttle itself has three big rocket engines that run on liquid hydrogen and liquid oxygen, stored in the big orange external tank, while the rest of the thrust is provided by solid fuel in the solid rocket boosters, a mixture of ammonium perchlorate (NH4ClO4), aluminum, iron oxide, and some binders to hold it in its moulded shape.

The liquid fuel engines fire first; they are the controllable ones. If there's a problem, they can be shut down. Once the solid fuel starts burning, they only stop by running out of fuel - and the solid rockets provide the majority of the boost to get the shuttle off the ground.

And since this is a chemical engineer's blog, I'm going to do some calculations around the chemistry of those engines. Of course, this won't be nearly enough to design your own rocket engine from, but then I'm just doing this for fun, I'm not a rocket scientist.