Quick aside: What does parts per million (ppm) mean?

What does parts per million (ppm) mean? Let’s say we have a new butter and we see that it has 100 milligrams of Vitamin E in 1 kilogram. This means we have 100 parts Vitamin E per million. 1 milligram is 1/1000 of a gram 1 kilogram is 1000 grams Therefore 1 milligram is 1/1,000,000…