You need to be careful on purchasing glycerin. The now version is Vegetable Glycerin. Unless it says USP, i would not use it. USP means it was packaged in a clean room environment and is safe for use in foods.
Some people advertise the product is food grade and correct it is, BUT they are just putting the glycerin from a larger container into a smaller container. No clean room. AND as we know anything can happen!
Find a USP KOSHER label product. This means a rabbi has blessed the whole process and it is a independent overlook of the packaging. Check out
www.VegetableGlycerin.com. They tell you more about USP, Kosher, and repackaged.