Packaging and storage
Preserve in tight containers, protected from light.
Assay
Transfer 5.0 mL of Spirit to a Babcock bottle, graduated to 8%, add 1.0 mL of kerosene, and mix. Add saturated calcium chloride solution, acidified with hydrochloric acid, almost to fill the bulb of the bottle. Rotate the bottle vigorously to ensure mixing, and then add a sufficient quantity of the calcium chloride solution to bring the separated oil into the neck of the bottle. Centrifuge at about 1500 rpm for 5 minutes, and read the volume of oil in the stem. Subtract five divisions for the kerosene added, and multiply the remaining number of divisions by 4.2 to obtain the volume, in mL, of peppermint oil in 100 mL of the Spirit.