Epsom salts dissolve slightly in rubbing alcohol but not to the extent they do in water. Some people apply Epsom salts and rubbing alcohol directly to their skin to relieve muscle aches, sprains and strains after taking part in sports. People with arthritis may add Epsom salts and rubbing alcohol to bathwater to relieve stiff, aching joints.
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Epsom salts dissolve slightly when added to rubbing alcohol, but they dissolve more readily in water because rubbing alcohol is less polar than water.
Epsom Salts Properties
Despite its name, Epsom salts are not true salt. Otherwise known as magnesium sulfate, it contains magnesium and sulfur (sulfate), but no sodium. Salt, made up of sodium and chloride, is a completely different substance. Magnesium is a mineral that helps keep the body working properly, regulating muscle and nerve function and making protein, bone and DNA. Epsom salts are so-called because they were first discovered in Epsom, England, and because they look like large pieces of salt.
Epsom Salts in Water
Like true salt, magnesium sulfate is highly soluble in water. Magnesium sulfate is an ionically bonded substance, made from positive magnesium ions bonded to negative sulfate ions. Water is described as being a polar molecule, meaning it has one side that is positively charged and one side that is negatively charged. In the case of magnesium sulfate, the positive part of water molecules attracts the negative sulfate ions, and the negative part of water molecules attracts the positive magnesium ions. This causes Epsom salts to dissolve quickly in water.
Epsom Salts in Rubbing Alcohol
Alcohol is less polar than water, particularly isopropyl alcohol (rubbing alcohol). This makes it harder for alcohol to dissolve the magnesium sulfate’s bonded ions. Also, rubbing alcohol is known as “bulky” alcohol, which makes it even more difficult for solubility to take place because the increased size of the alcohol chain does not create a stable environment for the mixing process. The result of adding Epsom salts to rubbing alcohol is that some dissolution takes place, but the Epsom salts do not dissolve completely. This makes it harder for the Epsom salts to be absorbed into your skin.
Epsom Salts Uses
Aside from easing sore muscles or soothing sunburned skin when added directly to warm bathwater, Epsom salts may be taken orally to promote a bowel movement or used to help remove splinters or bee stingers. You should consult your doctor before ingesting Epsom salts as a laxative, as the correct amount required varies, and some medical conditions and medications can react with Epsom salts.
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Claire is a writer and editor with 18 years' experience. She writes about science and health for a range of digital publications, including Reader's Digest, HealthCentral, Vice and Zocdoc.