Ordinary table salt (sodium chloride or NaCl) is still the most common and cheapest way to melt ice and still works fine. However, the old-fashioned standby is out of favor for burning plants, damaging concrete and getting into the water supply. It also doesn’t melt at as low a temperature as calcium chloride.
Other chemicals are also used in bags called Ice Melt. Potassium chloride (KCl), calcium chloride (CaCl 2) and magnesium chloride (MgCl 2) are more plant- and environmentally friendly.
What should one use? A professor of chemical engineering at MIT recommends potassium chloride (KC1) for paths and areas near plants. On driveways, for faster, more effective melting and higher concentrations, use calcium chloride (CaCl 2). Always read the list of contents on the bag.
Here’s the chemistry: Plain water freezes at 32 degrees F or 0 degrees C. When anything is dissolved in water, that lowers water’s freezing temperature. The more concentrated the solution, the lower the temperature before it freezes and turns to ice. For instance, it’s very hard to get l00 proof vodka to freeze at all, but don’t drink it cold because even though the vodka is still liquid, it would freeze your throat tissues.
Back to ice in the driveway. A 10 percent solution drops the freezing point of water by 10 degrees. Potassium chloride has a maximum solubility of 12 percent, magnesium chloride is 5 percent while calcium chloride’s is 32 percent. That’s why calcium chloride is faster and more effective: It’s more and gives the biggest bang per pound.
Ice Melt contains a mix of ionic salts, sodium chloride and potassium chloride and urea fertilizer (NH2 CO NH2), which is a sugar and acts as a binder. It’s not nearly as effective as ionic salts.
Another bag, called Quick Ice Melt, was only calcium chloride. The little white pellets in both bags looked the same.
All ice melts are poisonous if eaten and will irritate the skin. When handling, wear plastic bags on your hands, or gloves, and use a scoop to fill a shaker bottle.
When the ice melts to slush, shovel it off. The trick is to keep the surface clear and dry, which is no small task. Another trick is to put some pellets on the driveway and walkway before it snows. Shoveling will be easier because the lowest layer will be soft and slushy.
Sand, grit and ashes can be sprinkled on top as a quick fix. They last until the next rain or thaw and then freeze into the ice cover. They have to renewed frequently to be effective and safe.
Also useful are strips of old carpets laid atop snow while people are walking in and out. They are handy for temporary safety and quick cover-ups but may slide on slick, flat icy places. Obviously, they have to be taken in before rain, snow or melting and be kept under cover and dry when not in use.
A long cold snap early in the season is unusual though not unknown. The weather extremes in the Northeast seem more pronounced, which is one of the anticipated and understood effects of global warming.
To counter the effects of sodium chloride chemical burns on plants, flush the dissolved chemicals out with water.
In early spring, after the spring thaw and melting, turn on the hose or sprinkler and flush the area with a long flow of water. The idea is to move the dissolved ions deeply into the soil below the roots where the plants will not take it up. It can be done again if damage shows up later in the season.
Sodium chloride or any salt burn shows up as brown, dry areas on greenery, often after dry periods, especially in midsummer on tree leaves. Grass often turns brown completely and dies depending on the season and the concentration of chemicals in the soil.
For more gardening information, visit www.MothersGarden.net