It seems to me that I have read about this subject before so there may be something on the Web page about this from Ray however in the case there is not I hope this, lifted from about.com is informative.
Google is your friend! If you live in an area with a cold and icy winter, you have probably experienced salt on sidewalks and roads, used to melt the ice and snow and keep it from refreezing. Salt is also used to make homemade ice cream. In both cases, the salt works by lowering the melting or freezing point of water. The effect is termed 'freezing point depression'. How Freezing Point Depression Works When you add salt to water, you introduce dissolved foreign particles into the water. The freezing point of water becomes lower as more particles are added until the point where the salt stops dissolving. For a solution of table salt (sodium chloride, NaCl) in water, this temperature is -21°C (-6°F) under controlled lab conditions. In the real world, on a real sidewalk, sodium chloride can melt ice only down to about -9°C (15°F). Colligative Properties Freezing point depression is a colligative property of water. A colligative property is one which depends on the number of particles in a substance. All liquid solvents with dissolved particles (solutes) demonstrate colligative properties. Other colligative properties include boiling point elevation, vapor pressure lowering, and osmotic pressure. More Particles Mean More Melting Power Sodium chloride isn't the only salt used for de-icing, nor is it necessarily the best choice. Sodium chloride dissolves into two types of particles: one sodium ion and one chloride ion per sodium chloride 'molecule'. A compound that yields more ions into a water solution would lower the freezing point of water more than salt. For example, calcium chloride (CaCl2) dissolves into three ions (one of calcium and two of chloride) and lowers the freezing point of water more than sodium chloride. Here are some other de-icing compounds: Chemicals Used to Melt Ice Table with 5 columns and 9 rows Name Formula Lowest Practical Temp Pros Cons Ammonium sulfate (NH4)2SO4 -7°C (20°F) Fertilizer Damages concrete Calcium chloride CaCl2 -29°C (-20°F) Melts ice faster than sodium chloride Attracts moisture, surfaces slippery below -18°C (0°F) Calcium magnesium acetate (CMA) Calcium carbonate CaCO3, magnesium carbonate MgCO3, and acetic acid CH3COOH -9°C (15°F) Safest for concrete & vegetation Works better to prevent re-icing than as ice remover Magnesium chloride MgCl2 -15°C (5°F) Melts ice faster than sodium chloride Attracts moisture Potassium acetate CH3COOK -9°C (15°F) Biodegradable Corrosive Potassium chloride KCl -7°C (20°F) Fertilizer Damages concrete Sodium chloride (rock salt, halite) NaCl -9°C (15°F) Keeps sidewalks dry Corrosive, damages concrete & vegetation Urea NH2CONH2 -7°C (20°F) Fertilizer Agricultural grade is corrosive table end The New York Times Company. All rights reserved. ----- Original Message ----- From: [EMAIL PROTECTED] To: blindhandyman@yahoogroups.com Sent: Monday, March 03, 2008 9:14 PM Subject: [BlindHandyMan] Forwarded attachment... Well, from what I've been told... for what good that may stand... Sodium Chloride works, potasium cholride works to a colder temp, and the Ice Melt products work to abut 0 degrees. So with the following: I ask "if not on moisture, how does it work?" On Mon, 3 Mar 2008, Cy Selfridge wrote: > Could it be that when temps drop much below 10F the moisture tends to be non > existant and the salt has nothing to work with? > In Colorado when the temp drops below 10F the ice becomes crunchy and *very* > dry. > Cy, the ancient Okie... > > _____ > > From: blindhandyman@yahoogroups.com [mailto:[EMAIL PROTECTED] > On Behalf Of Lee A. Stone > Sent: Sunday, March 02, 2008 9:57 PM > To: blindhandyman@yahoogroups.com > Subject: Re: [BlindHandyMan] using rock salt > > > > > that was what I think I was looking for Bob" when I lived in Western > NY it did not work well near 10 degrees. thanks.Lee > > On Sat, Mar 01, 2008 > at > 07:47:09PM -0500, Bob Kennedy wrote: >> I never heard of a high temp that it wouldn't work at. Once you get above > 35 it's a bit of a waste because nature is melting the ice for you. >> >> I do remember from living in Western New York for many years that rock > salt doesn't work when the temperature is much below 10 or 15 degrees. >> ----- Original Message ----- >> From: Lee A. Stone >> To: Blind Handyman >> Sent: Saturday, March 01, 2008 2:19 PM >> Subject: [BlindHandyMan] using rock salt >> >> >> >> >> Am I correct that the standard store brands of rock salt or something >> like Hailite is a product that works at only below freezing temps? >> thanks.Lee >> >> -- >> Let's remind ourselves that last year's fresh idea is today's cliche. >> -- Austen Briggs >> Do you Jabber? I do. My JID is: HYPERLINK > "mailto:stonedge%40jabber.org"[EMAIL PROTECTED] >> >> >> >> >> [Non-text portions of this message have been removed] >> > > -- > No wonder Clairol makes so much money selling shampoo. > Lather, Rinse, Repeat is an infinite loop! > Do you Jabber? I do. My JID is: HYPERLINK > "mailto:stonedge%40jabber.org"[EMAIL PROTECTED] > > > > > > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.5.516 / Virus Database: 269.21.3/1306 - Release Date: 3/1/2008 > 5:41 PM > > > > No virus found in this outgoing message. > Checked by AVG Free Edition. > Version: 7.5.516 / Virus Database: 269.21.3/1306 - Release Date: 3/1/2008 > 5:41 PM > > > > [Non-text portions of this message have been removed] > > [Non-text portions of this message have been removed] ------------------------------------------------------------------------------ No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.516 / Virus Database: 269.21.3/1308 - Release Date: 3/3/2008 10:01 AM [Non-text portions of this message have been removed]
