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.

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.

Crystal habits

I am fascinated by crystals, particularly by their regularity. They basically consist of a unit cell that repeats over and over again, identically, across the whole span of the crystal. And if the crystal is big enough to see with the naked eye, that's a very large number of unit cells.

Very simple crystals, for example table salt (NaCl), have a tiny unit cell consisting of 4 atoms of Na and 4 atoms of Cl, arranged in alternating rows, a structure that is called face-centred cubic, because on each face of the cube, there's an atom in the centre of the same type as the atoms on the corners of the unit cell.

An interesting quirk of the simple 1:1 ratio cubic crystal structure is that you can define either Na or Cl as the corners of your unit cell, and it'll still be face-centred cubic.

Diamond's structure is also simple: every carbon atom has four links to four other carbon atoms, arranged in a tetrahedral shape around it. Because unit cells are defined as cubic or rectangular shapes, however, the diamond unit cell is less simple, even if the structure itself is simple.

Weird water

Water, despite the fact that it's incredibly common, is actually a pretty strange compound. Some of its stranger properties make it particularly useful for life, such as the way it switches from getting denser as it gets colder (normal) to getting less dense as it gets colder (not normal) below 4^oC.

A recently discovered and even more recently characterized weirdness of water is that on the nano scale and on hydrophobic surfaces, water spontaneously flows in instead of being expelled the way one would expect based on the usual reaction of water to hydrophobic materials: (blue in the image below)

Magnetic soap

This video demonstrates a nifty advance in surfactant science: unfortunately I can't include it here, so you have to click on supporting information then the .mpg video file link to see it.

What is shown on the right, sticking to the metallic disk being lowered into the liquid, is magnetic soap. (On the left is normal, non-magnetic soap.) The little yellow blob that lifted with the magnet-on-a-stick through the clear liquid and then fell when the magnet was lifted right out of the liquid, is the soap itself.

Three different non-magnetic surfactants were made magnetic by reacting them with ferric chloride, a common industrial chemical.

A solution of ferric chloride by itself also reacts very slightly to magnets, but it finds most of its use as a coagulant, not as a soap.

Violent separation

In keeping with my original plan for this blog, I am now going to teach myself something new.

Here is something I have known about and occasionally seen since I was a kid, and know the name of, but hadn't seen it in operation and didn't actually know how it worked until I decided to write this post and figure it out:

It works exactly the same way as this thing, which I saw for the first time as an adult:

Recycling water

It may be something we don't like to think about, but one of the things the astronauts have to do while in orbit will be coming more and more to Earth. Fresh water is limited, and getting more so with time. Water conservation helps, but it may not be enough in the future.

Whether they are dependent on well water or surface water, many cities have to worry about having enough water to last through the dry season as the water levels drop. Water restrictions are common in some areas; where I grew up, part of the summer routine was that you couldn't water your lawn whenever you wanted, but only on certain days. Sometimes there was an outright ban on watering lawns if the river level was too low.

At the same time, the volume of water leaving a city's wastewater treatment plant is a substantial part of what the city brought in to start with, and grows with population more than the season.

As wastewater treatment technology improves, the sewage plant's discharge gets cleaner and cleaner, so why not use it as feed for our clean water treatment system?

Life-giving crystals

Another piece of the puzzle that is life has fallen into place, and it is a spiky crystal.

That right there is one powerful crystal: it is the chemical precursor to RNA, the earliest self-replicating molecule that science is aware of, and thus the starting point for life. It grew from a mixture of basic, common organic chemicals in the presence of a few common amino acids, and is stable and will stay put until the next step, converting it to RNA, takes place.

Not only that, but it's the correct form of the two possible enantiomers that the RNA precursor can take, and it grew naturally out of a mixture of chemicals that didn't start out composed of the pure correct enantiomer, but of a racemic mixture plus a nearly racemic mixture of amino acid that had only 1% excess of the enantiomer they wanted.

New medicine from old

Traditional medicines can be interesting things. Some don't work at all despite being widely used, but some, like the bark and leaves of willow (Salix), work very well and have been effectively used for millennia—there are written records from 500 BC referring to its use. More recently (the 1820s) the active ingredient, salicylic acid, was produced, then in the 1890s acetylsalicylic acid, what we know as modern aspirin or ASA, was created. Aspirin no longer comes from plants as willow trees can't grow fast enough to sate the world's appetite for painkillers, but is now synthesized from phenols.

Another traditional painkiller, a milkwood (Tabernaemontana) has been under investigation for several years now. According to the studies, it contains a mixture of several things, including compounds in the class of opioids (a painkiller type which tends to have undesirable side effects and which causes addiction) and conolidine, among many others.

The conolidine and other compounds were isolated and identified in 2004, but conolidine couldn't be properly studied at that time because they only managed to get a 0.00014% yield when purifying it out of the plant. In May 2011, a team of researchers from the Scripps Research Institute announced that they had not only managed to synthesize conolidine, they had also tested it on mice and found out that it had painkiller effects as strong as morphine, but without any of morphine's adverse side effects.

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.