| This book started in my shower.
The label on my shampoo bottle listed many compounds, and, due to my interest in chemistry, most of them were familiar or had obvious functions. However, one compound stood out as puzzling: sodium chloride.
Why was there salt in my shampoo?
Since I wasn't likely to be eating it, I doubted it was for seasoning, despite the strawberry aroma of the liquid. It could have been used as a preservative, but the remaining ingredients were more likely to kill microbes than salt was.
Once dry and dressed, I was still curious, so I wrote a letter to the manufacturer asking why there was salt in my shampoo. I received a surprisingly enlightening response from the company. Someone there had actually discussed the issue with a chemist and sent back to me an answer that made sense.
The ingredients in the shampoo come from many different manufacturers, in many different places around the world. From day to day, a particular batch of shampoo may differ significantly from the previous day's batch in the amount of moisture brought in with those ingredients. Salt has the effect of thickening the mixture, and is added to each batch in the amount needed to raise the viscosity to a specified level. Consequently, the customer gets a product that pours the same way each time. This consistency is important to the customer, because a watery product can cause suspicions about value or about possible tampering. |
