Nicotine salt is the natural form of nicotine found in tobacco leaves. Nicotine derived from tobacco leaves is slightly acidic with a pH of approximately 5. However, the most commonly used form of nicotine in e-liquids is called freebase nicotine. Freebase nicotine is slightly basic with a pH of approximately 8. The pH scale ranges from 0 to 14 where lower pH values indicate a more acidic substance, while higher pH values indicate a more basic substance. The chemical process for making the nicotine derived from tobacco leaves more basic is called de-protonation. This is the process that turns a natural nicotine extract into a freebase nicotine extract.