My knowledge of chemistry is nothing compared to my knowledge of cheesy 1970’s TV. One of my favorite 70’s commercials is for something called Calgon, a water softener. The commercial can be seen by clicking here. In short, a customer asks a Chinese laundry shop owner how he gets shirts so clean. He replies that it’s an “Ancient Chinese Secret.”
I wondered about this “Secret” for years – what was Calgon doing? How does it get shirts so clean? How is it related to water softeners that people have for well water in their homes? Why does water need to be made softer? Hence I had a ton to think about while I was trying to pay attention to The Brady Bunch and Partridge Family Hour (8 pm to 9 pm – Saturday nights).
Hard water is water with a high mineral content – particularly calcium and magnesium ions. These minerals aren’t at all harmful to people, but they can form deposits inside of pipes, hot water heaters, cooling towers and they cause soaps to not lather and clean effectively.
Most soaps are salts of stearic acid or laurel hydrogen sulfate – long chained carboxylic or hydrogen sulfate acids. When put into water, they act as surfactants – allowing greasy dirt to dissolve in water by making structures called micelles – the hydrophobic tails of the acids associate together to form a hydrophobic/greasy environment (this is where the dirt goes); the hydrophilic heads of the acids point out towards water allowing the micelle to dissolve in water.
The calcium or magnesium in hard water takes normal sodium stearate soap which can form micelles and makes a much less water soluble compound, calcium stearate, which precipitates out as what we know as soap scum. Now we have fewer micelles to help clean and more soap scum to clean up afterwards. Calgon itself was named for the phrase “Calcium Gone” and is actually sodium hexametaphosphate – the hexametaphosphate anion complexes particularly well with calcium and magnesium leaving sodium in its place. Now the micelles can form, we have soap that works as expected and no deposits on inside of our plumbing – Hooray!
The water softener in my house for our well water is just a bucket on sodium chloride (table salt) – same idea as Calgon, but not as fancy – the sodium chloride scrubs out the hard minerals in our well water replacing them with sodium.
It took a lot of time and a bit of research, but one of the mysteries of the ancient world has been solved.
Adam Gilbert said:
Jill – I think they work the same (sodium chloride vs. potassium chloride) as both sodium and potassium are soften than calcium and magnesium.
on September 24, 2011 at 1:58 am
Yadira Roman said:
I like Think Since Now very much, it has been editing very interiesting topics like Science Projects, the ones related to autismm and many more. I always take a few minuts to read them. Thank you very much for publishing all this short but very interesting themes.
on September 23, 2011 at 4:27 pm
Jill Chabala said:
Does the potasium chloride work the same way as the sodium chloride or is it less/more effective?
on September 23, 2011 at 10:43 am
Elaine Tai said:
Thank you for the informative article. The wonders of salt (sodium chloride). No wonder the humble “salt” was once considered as equivalent to gold for during human ancient civillation.
on September 23, 2011 at 3:17 am
Mohamed Salem said:
Very interesting, thanks for sharing.
on September 22, 2011 at 8:21 pm
Victor said:
Thanks Adam for this different (humorous) history lesson on a science that was mostly familiar to me, but will more likely stick for future knowledge and even trivia answers due to the visual language you used.
on September 22, 2011 at 8:05 pm
Candace Broach said:
So cool! Thanks Adam!
on September 22, 2011 at 7:54 pm
Carp Mirela said:
Very interesting theory! In my country , my grandma used sodium cloride when washing white clothes! And she had no idea about chemistry!
on September 22, 2011 at 7:10 pm