Glycerol – the Halloween edition
1 August 2025
Just in case you have not used glycerol before: it is supposed to be a crystal clear liquid that is quite viscous and feels very heavy because it has a high density. In molecular biology it is used in all sorts of contexts, but we use it mosed as an antifreeze for bacterial stock cultures, so it is quite important that it is pure to avoid contamination and/or stressing bacterial cultures, which are not too happy in high concentrations of glycerol anyway. It means that we order glycerol on quite a regular basis, usual from Merck via my favourite laboratory equipment supplier SLS.
The latest shipment arrived today. A 500 ml bottle with the correct label. The viscosity? Perfect. The density? Spot on. But why does the liquid look like it has been filtered through a traffic cone?
It looks like this glycerol has been infused with the essence of Halloween.
What really gets me here is that quite obviously two quality control systems have failed. How it ended up on Merck's shelf in the first place would be interesting to find out, but some poor soul in packaging looked at this bottle of what is essentially laboratory-grade Tang and thought, "Yep, this checks out. Nothing suspicious here. Just some perfectly normal neon-orange glycerol. Ship it!" Either the person packing the items has absolutely no understanding of what they are. There are thousands of chemicals, of course, and few will know how they should look like, but some are more common than others. Plus, when I grew up glycerol was indeed a relatively common household item, as it was used to keep any type of rubber from degrading.
I suspect it is much more like how Seth Godin describes it: the person will simply think that it is not his job to care.
I am interested to see what the customer service response to my query will look like.
Update 18/08/25: Well, Merck has seen the error of their ways in so far as they have shipped a replacement bottle, this time in acceptable condition. However, they have offered no explanation as to what happens. Apparently it can degrade:
"Once the glycerin decomposition reaches a significant level, the material will turn yellow."
And:
"When using a less pure grade of glycerin a yellow discoloration occurs almost immediately (within 24 hours) if the temperature exceeds ~50–55 °C (~122–131 °F)."
Note the "less pure grade of glycerin". So heat and less pure grade of glycerin. One wonders whether the higher prices of Merck are justified.