That is what Lowes on Rt106 W Bridgewater was pushing as DeIcer! Obviously they were out of the standard calcium chloride...

Bingo thats the place, it worked and was only a little over $5 for a 40lb. bag.

I didn't have ice dams or leaks, but I did have frozen solid gutters. I got up there with a ladder and a shovel and cleared off the snow about six feet up from the gutter. With the warm weather today - 43 degrees - the ice in the gutter melted no problem. The only problem I have is when the gutter freezes up and the melt water from the snow runs over the gutter and down the outside of the house. No problem today, but I still have ice in the back gutters - less sun back there.

I have electric heat wires on the roof and in the gutters.. i rake after every snow fall... I have the only house on the street with out ice dams....

the reason for CaCl is because it relies on a chemicle reaction to work ( just add water) rock salt requires help from the sun and warmer temps...

My lawn is crab grass.... i couldnt kill it if I wanted to...

Rock salt is Sodium Chloride - NaCl. Calcium Chloride is CaCl2. When NaCl dissolves, there are two ions - one of Na and one of Cl. When CaCl2 dissolves, there are three ions, one of Ca and two of Cl. That's why Calcium Chloride works better. Both are chemical reactions - they lower the temperature at which water freezes - so they cause ice to melt as long it the temperature is above the new freezing temp.

Look at the size of the brain on mark!

BSD-135: Ice Dams — Building Science Information
This site is worth looking at when you try and figure out what to do to permently solve your problem

I hate to nitpick, but isn't dissolving a physical change? You mix table salt into water, then evaporate all the water and you'll still have table salt. If it were a chemical reaction, then a new compound would have to be created.

Dissolving salts into water raises the boiling point of water and lowers the freezing point. I believe calcium chloride lowers the freezing point more than NaCl would and is why it is more effective at dealing with ice.

I always loved chemistry in college is high school.

No quite correct, JD.

Is mixing calcium chloride and water a chemical reaction?
Answer YES

CaCl2(aq) + H2O(aq) = 2HCl(aq) + CaO(s)

You con't get CaCl2 back.

More importantly for melting snow: the reaction is exothermic giving off HEAT.

http://www.youtube.com/watch?v=GYy9B...layer_embedded

(thermometer is in Celsius)

All I know is that working all day with two other guys and plenty of calcium Chloride got most of the ice dams off of my roof.

that made me chuckle out loud... have no idea why. :rotf2:

That's right, forgot CaCl2 is one that actually reacts with water.:smash:

Is it called the eutectic point ?
Haven't thought of it since Charlie Waughs 1972 chemistry class, all I wanted to do was burn stuff . . . . . boy did I ever.:grins:

Nope , you had it right Johnny D.

When we use either CaCl2 or NaCL to melt ice , its because it lowers the melting point of the water. There is virtually no contribution of an exothermic reaction at the very low levels it gets diluted to when you use a sprinkle of salt on an icy surface. yes , a spoon full in a small amount of water will raise the temp but for the use in melting ice , its all Phase diagram stuff , not exeothermic reaction. It actually will lower freezing point to -50 degrees at a 30 wt% solution but my guess is that at the concentrations we use , it might lower it 4 degrees or so.

The experiment to prove this using the video shown , would to be to put the reacted mixture that was raised to 50C inot a freezer. The freezing point of the water would be way low , maybe approaching -50 C at the concentration he used. Remember , in the freezer you are not taking the salt out. You are just taking heat out and even though all the heat of the reaction is gone , the water with the same salt in it still has that hugely lowered melting point.

To read more , search for "water/Calcium Chloride Phase Diagram.

Saltheart
MIT 77 :)

Didn't see makai's post.

the eutectic point is that specific concentration of salt and water that has the lowest melting point of all the possible concentrations. It aloso needs to transform from a total Solid to a total liquid to be a Eutectic point. If it is at a concentration that turns to slush , some water and some solid , its not a eutectic point , its just some point along the partial fraction liquid + solid phase line.

Eutectic= complete solid to liquid transformation on heating at one specific concentration where the melting point is the lowest

Think my head just got a little bigger,
now I wanna make some homemade ice cream the old fashioned way !

So... Phil and I are both kind of right?

I like that...on a grand scale. I'm a single molecule scale guy!

If there is no water and its below freezing...each crystal/molecule CaCl2 on a molecular scale reacts with snow/ice to generate water based upon mini-exothermic reactions, e.g. ice melts. The thing cascades and makes more water which dissolves more CaCl2. The more water the more CaCl2 dissolved the lower the freezing point which causes more ice to melt.

I am confused, doesn't the solid calcium chloride generate heat untill it becomes liquid when exposed to water, either solid or liquid?

Stay confused, sometimes we are better off that way!:rotf2:


Point 1: yes when adding solid/dry CaCl2 to water it will get warmer. The more CaCl2 the warmer it gets. The mixing is "exothermic".

Point 2: CaCl2 in water will lower the freezing point of that water. Again, up until 30% (w/v) that freezing point depression will eventually reach -50C. (Question: anyone know how cold -50C is? DAMN COLD!)

When determining the freezing point (or eutectic point) of a given solution of CaCl2 in water it doesn't matter at what temperature the CaCl2/water solution starts from, it is not a measure of how many BTU's to cool only at what point does the solution freeze. So if I take room temperature water, add CaCl2 depending upon how much CaCl2 it may get detectably warm (to the hands or see movie above), then cool it down to freezing it will still have the same measured freezing point whether I start from room temperature water, warm/hot water, or even cold water. The graph attached earlier takes 20 or more different solutions of CaCl2 in water and measures the freezing point of each solution.


Side point: Car antifreeze, ethylene glycol, if you mix 2 parts anitfreeze with 1 part water you get a solution that freezes at ~70C. Don't mix ratios in any greater as the freezing point rapidly rises!

Here is another solution. I take all my rigged eels which have been soaking in brine solution for years and place them on the ice dams. They slowly emit brine solution and keep my gutters free of ice. As long as it's cold the eels stay fresh - just don't leave them on your roof in the spring time. :)

DZ

I honestly don't know about what happens when the first solid water and solid CaCl2 meet. What you need to think of is all the CaCl2 he had to add to just 50 CC of water to get a 25 degree rise. All that saly would have melted 100 times more water do to the lowering of the freezing point where as that much heat 50 CC X 25 degree rise at 1 cal per degree =1250 cal. That isn't much heat when you think of all the area of snow , the weight of the ice , the latent heat of fusion of the water which is 80 cal /gram (1gram of water is 1 CC) . The exothermic heat is just such a drop in the bucket that its effect in melting real ice amounts on a roof or road , etc is negligible. I will give you that there may be some roll of the heat of reaction in initiallizing the process as I'm just not at all sure but my gut reaction is that even that is not true or if true again almost insignificant beyond just getting the first few molecules of water to go liquid.

But anyway , I think we all now have enough Physical Chemistry knowledge of the salt/water reactions and Phase equilibrium to last us a lifetime. :)

DZ- THAT IS CLASSIC:rotf2::rotf2::rotf2::rotf2:

The one point of the building science thing that I posted is that the reason you get icedams is you are losing heat thru the roof. If you do the things they suggest you will 1. Not have ice dams 2. Save money on fuel. Sometimes the cure can be done in less time than it takes to chop off ice dams. Most airsealing and insulation upgrades are pretty low tech.

where would we be without PRBUZZ to straighten us out on all things involving chemistry and hot babes?

The most important point of all. I had cracks running up the corners of four closets that I finally patched this year. That warm air getting out of the rooms and in to the wall interiors goes straight up to the attic. I also taped over all the unused wall sockets. Add this to the attic insulation I've done in the last couple years and I've got more snow on my roof than any neighbor - because my attic is so cold. I did get ice in my gutters, but none on the roof itself, and no water leaks.