Friday is here, and the weekly 'Weekend Science Bite' column is back — number 61.
This time: iodine, its reaction with titanium, and the connection to table salt and spacecraft fuel.
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Iodine is a fascinating substance, and we all know it from the medicine cabinet.
In the human body it concentrates in the thyroid gland, where it is oxidized and reacts with proteins in a complex process to produce essential hormones.
Iodine deficiency causes the thyroid gland to enlarge, as it attempts to absorb greater amounts of iodine from the bloodstream.
Because of iodine's critical importance in preventing disease, a small amount is now added to commercially sold salt, and the problem of iodine deficiency has been significantly reduced as a result.
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In the video you can see what happens when iodine is combined with titanium.
Iodine powder consists of molecules made up of 2 iodine atoms each.
In the reaction with titanium, the molecules break apart, and each titanium atom bonds with three or four iodine atoms, releasing a large amount of excess energy in the process.
The energy released causes the mixture to heat up, and when iodine is heated it converts directly from a solid to a purple gas without passing through an intermediate liquid phase.
Some of the titanium reacts with the oxygen in the air and becomes titanium oxide.
Titanium oxide is used industrially to produce white paint, and it is what gives some of the fumes their white color.
The sparks produced in the process are micro-explosions of energy release, and the overall result is the spectacular pyrotechnic display seen in the video.
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Radioactive isotopes of iodine are used to treat thyroid cancer, because the body naturally concentrates them there.
Iodine is also found in anti-radioactive-poisoning pills, because a high iodine content in the thyroid gland prevents the absorption of radioactive iodine that could be dispersed into the air in the event of a nuclear reactor malfunction.
An interesting application being explored for iodine is as spacecraft fuel, because it can be stored as a powder under temperature and pressure conditions far more convenient than those required for other rocket propellants, and it converts directly from a solid to a gas at a relatively low temperature.
In addition, iodine's storage density is particularly high, which significantly optimizes how efficiently it can be stored.
And above all, iodine is an inexpensive and abundant element to produce — by some estimates, the oceans alone release several million tons of iodine into the atmosphere every year.
Shabbat Shalom ☺️
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