Preparing the Hydnocarpus Oil Injection Treatment. Preparation of esters from oils. To the right a mixture of oil, alcohol and acid are being boiled over a water-bath; reflux condenser above. In the middle the esters are being washed in a separating funnel. The upper layer is the esters and the lower is water. To the left a bottle has been adapted as a separating funnel. Such a bottle should be used for preparing the esters by the cold process. NLM Unique ID 25960700R.