Sunday, February 8, 2009

Don't eat that orange snow

I was surprised to find an answer to an enduring mystery in the pages of the COD newspaper, The Courier. During the almost perpetual snowfall that has characterized our winter which, in the blink of an eye, disappeared with the rapidity of a morning dew this past spring-like Saturday, we had noticed our street turn a deep amber. We ascribed the color to a mysterious de-icing agent that appeared to be applied specifically to our street, but to none of the others in the neighbourhood. One left the virgin white of Raintree and entered the amber of Raintree Ct., the line of demarcation being the 4-way stop sign. This substance was quite soluble and inevitably ended up in the garage where it would lie in dark brown pools. It would give off a distinctive caramel odor, a sort of echo of distant baking; and, as the water evaporated, a carpet of fine crystallites coated the concrete. I noticed the same substance over at the college last week and this week's Courier provided an explanation as to what this mystery substance is. It is in fact, according to the paper, a brine/beet solution called Geomelt.

The paper uses the term "organic" to describe it, and later states that it is "all natural," adopting the buzzwords of the health-food aisles to promote snow melting. Exactly what distinguishes organic salt from non-organic salt is unclear. Any one of my chemistry students would be able to tell you that salt is not organic in the chemical sense, being of course the archetype of the inorganic compound. Of course the term "organic" in the supermarket has a different connotation referring to the method of husbandry: the absence of mass-produced fertilizers and insecticides and so on. It's definition is a bit murky, and war has been waged between the true organics and those fake organic interlopes who wish to exploit the term to sell non-organic produce. Exactly how the production of salt would be organic is unclear. It is either dug from the ground, scraped off a salt-flat or extracted from ocean water by evaporation.

The claim is that the Geomelt will work to much lower temperatures than regular rock salt. As my more advanced chemistry students will be able to tell you, the freezing point depression of a solution depends simply on the concentration of particles. I believe the origin of the Fahrenheit scale, so beloved of our weathermen (meteorologists not Bill Ayers) was set at the freezing point of a saturated salt solution. So the claim that Geomelt works at -25 degrees F is quite surprising. Which brings me to the question of the role of the beet juice - the second ingredient in the mystery mixture. Why beets? Presumably, the soluble components are various carbohydrates, large molecules compared to salts that aren't that effective because they do not ionize in solution.

I noticed that the COD folks had gone around spraying the sidewalks with this stuff, leaving sticky brown trails. Perhaps the role of the beet is to glue the salt to the sidewalk, not to mention the soles of one's shoes.

No comments: