What do moisturizers & ink cartridges have in common?

This week I had some extra time at home so I turned to household items for scientific inspiration. Looking around at all the lotions in my bathroom and bedroom, I realised I knew very little about what was inside them. Time to squint at some ingredients lists! To my surprise, over half of them contained a common ingredient (apart from water/aqua). I found it in sun-cream, deodorant, shaving gel, moisturizer, hand-cream, after-sun, body butter, bruise first aid cream and even shampoo.

Carbon (C) = Grey, Hydrogen (H) = White, Oxygen (O) = Red

This seemingly universal ingredient is listed as glycerin but is also known as glycerol or glycerine. It has a simple chemical structure made up of  3 carbons (C), 5 hydrogens (H) and 3 hydroxyl groups (OH). This gives it the formula C3H5(OH)3. Glycerin’s official chemical name is Propane-1,2,3-triol which sounds extremely complicated but when broken down is quite simple. Propane is a chemical with 3 carbon atoms. 1,2,3 means that hydroxyl groups are positioned at carbon 1, 2 and 3. The final bit, triol, indicates there are 3 hydroxyl groups in the chemical. These hydroxyl groups enable glycerin to be water-soluble which is important as all of the lotions in my house contain water as their main ingredient. Glycerin is plentiful as it is a by-product of both biodiesel and soap making.

So now I’ve found out what glycerin is, why is it such a common ingredient? Its chemical structure is a clue. The hydroxyl groups which allow glycerin to be water-soluble, also give it another useful feature. You can feel the chemistry as water is attracted to and holds onto glycerin. Companies all over the world exploit this feature in their skin products. The skin’s outer layer can become dry due to excess water loss. Glycerin treats and prevents this by drawing moisture from the body into the upper layer and preventing it from evaporating.

Glycerin-containing products in my bathroom

Personal care companies are not the only businesses finding uses for glycerin. To my amazement, there are 981 products that contain glycerin listed in the United States Household Products Database. These range from ink cartridges to toilet cleaning gel. Another of its many applications is as a food sweetener to replace sugar and as an ingredient in the explosive, nitroglycerin. All these uses have been built up over 230 years as glycerin was first discovered by Swedish-German chemist, Carl Wilhelm Scheele, in the 18th century.

My adventure inside my house this week has convinced me that science can be found in seemingly ordinary places. Glycerin shows the impact that chemistry has on our everyday lives. The variety of uses of one relatively simple chemical is mind-blowing. Check the ingredients next time you open one of the many bottles scattered around your house.  There’s a good chance you’ll find glycerin in the list!

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