The Basics of Distillation

Distillation separates liquid mixtures based on the differences in boiling points. It is a simple procedure which can be used to purify water, wine and alcoholic beverages. It is also employed in industrial applications such as oil stabilization.


During distillation, the glassware can break and the hot vapors may burn the operator. To prevent this a system with standard taper connections between the condenser and the receiving vessel must be used.


Ethanol is produced from the fermentation of various substrates including starchy grains such as corn, wheat, rice and barley. It can also be made from lignocellulosic biomass such as corn stover (stalks and leaves), perennial grasses such as Miscanthus and switchgrass, and wood waste. Ethanol is used in alcoholic beverages, food processing, pharmaceuticals, fuel for internal combustion engines, and other industrial applications.

During distillation, ethanol and water are separated by boiling the mixture in a round-bottom flask with a Bunsen burner under it. The ethanol-water vapor is then condensed into a liquid by cooling it. The ethanol-water solution is then separated into a number of separate fractions by distillation.

Ethanol is a volatile, colorless, odorless substance with the chemical formula CH3CHOH. It has a low boiling point, is hygroscopic, and can dissolve many ionic compounds such as sodium chloride, magnesium chloride, and calcium chloride. It is also soluble in nonpolar solvents such as acetone and chloroform. Ethanol is used as a cleaning agent, in mouthwashes and soaps, to make perfumes, and to prevent skin infections. It is also present in certain alcoholic beverages such as beer, wine and spirits. Chemical and sensory analysis techniques, such as near-infrared spectrometry, high performance liquid chromatography, gas chromatography and olfactometry are used to test the quality of alcohols.


Esters are formed when alcohols react with carboxylic acids losing a molecule of water in the process. Carboxylic acids are found in fruits, vegetables and grains, while alcohols can be made from any organic compound such as sugar or starch.

Esters have a very low boiling point compared to other constituents in the mixture and are separated by raising the temperature and allowing the ester to evaporate into a gaseous form that is collected in a separate vessel. They can be distinguished by their aroma which is often fruity. Larger esters have a more industrial smell (ethyl acetate for example) while shorter chain esters smell similar to an organic solvent such as methyl ethanoate.

They are commonly used in the distillation industry as a high-grade organic solvent and in some perfumes and pheromones. They also act as lubricants and are one of the main ingredients in artificial lubricants such as WD-40. They are also found in a variety of food products such as salad dressings and candies. An ionized ester can be identified in the IR spectrum by its intense sharp peak at 1730-1750 cm-1 corresponding to a carbonyl group.


When distilling, a distiller is often faced with the decision of which fraction to collect. It is important to cut a portion of the still’s output between heads and hearts (or tails) at the right time, as this can have a big impact on the quality of the final product.

Using simple distillation, a liquid can be separated from other liquids by boiling the components at different temperatures. The liquid vapors are then channeled into condensers, where they are cooled down and condensed into separate fractions according to their boiling point. This process is known as Raoult’s Law.

The Heads Fraction is a mixture of methanol, acetone, and ethyl acetate with some ethanol as well. It’s typically blamed for hangovers and has a harsh, solvent like sting to it. It is not recommended to use this in a drink but if you do, be careful. It can also be used to clean the inside of new stilling equipment and around the house/shed as it is a great solvent and cleaner. For best results, save this in a jar and only use it when needed.


The hearts fraction contains a lot of ethanol and has a smooth taste that lacks the harsh bite of the heads. The skill of the commercial distiller is knowing exactly when to start collecting this portion of the run. This can be determined by time, temperature or a combination of both.

This is one of the many reasons that a good commercial distiller is in high demand and is well paid. It is not only an art but also a science to know exactly when to cut from heads to hearts to tails.

The tails contain the fusel compounds that give off unpleasant and undesirable flavors. This part of the run can also be contaminated with methanol, which is very toxic. Methanol is a highly volatile substance that can cause blindness in a matter of seconds, so it is incredibly important that this part of the run be kept to a minimum. The tails are usually saved and mixed with the hearts of several runs to create a new-make spirit that is barreled. Alternatively, it can be used in non-consumable products.


Acetaldehyde is an aliphatic aldehyde with two carbons, four hydrogens and one oxygen. It has the molecular formula CH3CHO and its formyl group – CHO binds strongly to the proton forming an amide linkage with the hydroxyl groups of water and other organic compounds. It is soluble in alcohol and is easily detected with the Tollen’s test (see below).

The first vapours to form during distillation are those with the lowest boiling points, these are known as the heads or foreshots and are removed from the flow before the more desirable ethanol alcohol forms in the heart. The tails are a collection of bitter alcohols, including propanol and butanol, as well as amyl alcohols and furfural (not an alcohol), these are more likely to be discarded from the distillation process or used as raw material for industrial purposes.

Acetaldehyde is toxic at high concentrations and causes damage to DNA which can increase a person’s cancer risk. At low concentrations it can irritate the skin, eyes and mucous membranes, and cause headaches and nausea. It can also be inhaled and can aggravate the respiratory tract, with symptoms occurring at concentrations as low as 1000 ppm.