Friday, December 21, 2012

Another Curveball - Wonky Addendum

One of the criteria I use for judging whether a reporter knows what he’s talking about is the way he uses words. In science, words are used very precisely, some of them the same words that are used in everyday conversation. I recognize that reporters may try to simplify complex concepts for their readers; but they need to understand what they are simplifying. I also look for problems of logic and sequencing: has the reporter thought out how an activity must happen?

Here are two of those problems in David Ignatius’s article on Syrian chemical weapons.

Ignatius says “combine and activate the chemicals” at least twice. This is not something that someone who understands much about chemistry is likely to say. It’s a common mistake: not understanding chemical reaction. There is a difference between mixing and reaction. When you spoon sugar into your coffee and then stir, the sugar disappears as a solid, although you can taste it. It is mixed into the coffee, but it doesn’t react, it remains a separate chemical compound. When you are making a cake, you mix the ingredients. Some of the leavening ingredients start reacting right away, making the batter frothy with carbon dioxide, but most of the reactions take place during baking to make the liquidy batter into a solid with lots of porosity.

Some reactions take place quickly. You can mix vinegar and baking soda and watch the carbon dioxide froth out. But sugar in coffee is a mixture without reaction. When substances react, their chemical bonds rearrange to make something new. That’s how you get safe, edible salt (sodium chloride) from a soft, reactive metal (sodium) and a poisonous green gas (chlorine).

For a binary nerve agent, two precursors are manufactured that, when mixed, react to form the agent. Ignatius’s formulation, “combine and activate the chemicals,” doesn’t make sense. Combining the precursors activates them. Or, more accurately, produces the nerve agent. To a chemist, “combine” could mean mixing OR reaction, and, if it’s reaction, it doesn’t describe this kind of reaction. Mixing the precursors activates them. There’s no need to add red mercury or say magic words over them, or whatever “activate” means to Ignatius.

And that’s why nobody who knows chemistry would say it that way.

The more I think about these reports that Syria has binary precursors to chemical agents, the less credible they seem to me. Binary precursors require manufacturing two components, rather than just one. The two components require separate storage. Mixing them to form the agent and loading shells would require about the same equipment that a unitary agent would require. The capital requirements and number of steps are more than for a unitary agent.

Shells that mix binary precursors in flight are difficult to design and manufacture.

It’s difficult to see why a not-so-rich country would go to all this trouble. Not impossible, of course, but Occam’s Razor suggests that the stories of binary precursors being mixed before loading into shells are nonsense.

Cross-posted at The Agonist and Nuclear Diner.

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