Putting salt and ice on arm?!
Question: Why does it burn when you put salt and ice on your arm?
Answers: Why does it burn when you put salt and ice on your arm?
Adding salt to ice makes it colder. A technique used in chemistry labs everywhere, adding the salt to the ice melts it. The melting process requires energy, in the form of heat (latent heat), to achieve the phase transition, a good way to think about this is the ice staying the same temperature but drawing heat from its surroundings to become a liquid. If you look at wikipedia it should explain the thermodynamics.
If you are talking about putting salt and ice on a cut or graze this hurts for two reasons:
1) The temperature, via temperature sensitive nocireceptors (pain producing neurons)
2) The sodium and chloride ions of the salt perterb the membrane potential of all of the nocireceptors (not just the temperature sensitive ones) in the area, causing pain signals to be sent, this isn't normally possible as the skin usually prevents external ions from reaching nerve cells.
EDIT: Oh, and salt is a good disinfectant because it sucks the water out of bacterial cells via osmosis, the stronger the solution the better the disinfectant. (This is not an entirely dissimilar mechanism to the salt-pain, both can be modelled by using the Nernst equation along with some fundamental properties of the cell membrane). Ethanol disinfects for the same reasons, by sucking the water out of bacterial cells. Ethanol can be better because it can be pure, without much water content, whereas, salt can usually only be as concentrated as the saturation point of the solvent.
Most likely, the salt is having a chemical reaction w/ the ice, and it is sticking to your arm, or on a wound, the salt is disinfecting it and the ice is cooling it.
i know eh.. i'm not sure though!
Hmm i think it's the disinfecting agent within salt that makes it sting on open wounds or even skin if you keep contact with it to long. I know salt is great for things like cleaning out wounds and preventing infection and so is alcohol so maybe there both somwhat alike because they both sting. I tried actually looking this up before and not many people knew what is within salt water which makes it such a good disinfectent so without any ingredients i can't really help you with what the exzact ingredient within salt makes it sting. I know salt is made up of many minerale though especially salt water in seas and oceans. I'm talking almost every mineral known to man because it gets its minerals from the ground and the sea bed floor. Do more research and maybe you can find which exzact mineral causes the stinging.
Also if you have any acne go and take a soak in a sea or the ocean and i guarentee you'll see much improvment!
I dint know but I have never heard of salt and ice on your skin, don't do it anymore