One drop in a liter or water wouldn't do that much. Clove oil is used 1-5 drops at a time in 2 ounces or so of water, while pure oregano oil is typically used a drop or two at a time in 2 ounces of water. I would want to use at least a drop at a time in 2 ounces of water for ginger oil or lemon oil, but am wondering if much more can safely be used. I haven't seen anything about toxicity for ginger oil or lemon oil, however more than a drop at a time might be too much. I guess I will need to experiment on my own.