Question

What is meant by rectified spirit? How is absolute alcohol different from rectified spirit?

Short answer

Answer: Rectified spirit contains around 95-96% alcohol by volume and has undergone multiple distillations, while absolute alcohol is almost pure ethanol with an alcohol content of 99.5% or higher, having undergone further processing to remove residual water content. Absolute alcohol is considered more pure than rectified spirit.

Step-by-step solution

Definition of Rectified Spirit

Rectified spirit, also known as neutral spirits or rectified alcohol, is a highly concentrated ethanol which has been purified by multiple rounds of distillation. It typically contains around 95-96% alcohol by volume (ABV).

Definition of Absolute Alcohol

Absolute alcohol, also known as anhydrous alcohol or pure ethanol, is ethanol that contains no more than 0.5% water by weight. This means it has an alcohol content of 99.5% or higher, and it is obtained by further processing and/or chemical drying of rectified spirit to remove the residual water content.

Difference between Rectified Spirit and Absolute Alcohol

The main difference between rectified spirit and absolute alcohol is their alcohol content and the extent of purification. Rectified spirit has an alcohol content of around 95-96% ABV and has undergone multiple distillations, whereas absolute alcohol is almost pure ethanol with an alcohol content of 99.5% or higher, and has undergone further processing to remove residual water content. Absolute alcohol is considered more pure than rectified spirit.

Key concepts

Ethanol Distillation

Ethanol distillation is a process used to purify ethanol by separating it from a mixture - typically from water and other components. This process takes advantage of the different boiling points of the substances present in the mixture. Ethanol has a boiling point of 78.37°C at standard atmospheric pressure, which is lower than that of water.

This separation process begins in a distillation column, where the mixture is heated until the ethanol evaporates. The vapor then travels up the column and is cooled and condensed back into a liquid, which is collected at the end of the distillation process. To obtain higher purity, the distillation is often carried out multiple times. This is where terms like 'rectified spirit' come into play. It has been distilled multiple times to reach a high level of ethanol concentration, typically around 95-96% ABV.

Students should understand that distillation is not just a simple boiling process but involves careful temperature control and often requires specialized equipment. The objective is to isolate the ethanol from other substances in a controlled and efficient manner to prevent loss and ensure purity.

Neutral Spirits

Neutral spirits are called so because they have no added flavors and possess a neutral taste and aroma. Produced from grains, grapes, beets, or other products containing sugar, they undergo a rigorous distillation process to achieve high alcohol purity and are often referenced as the base for many types of distilled spirits and liqueurs.

Rectified spirit, as mentioned in the aforementioned steps, is one type of neutral spirit. Containing around 95-96% ABV, rectified spirit is used in various applications such as the production of liqueurs, blending with other spirits, or serving as a base for infusions. Furthermore, because neutral spirits have no distinctive flavor or odor, they are perfect for producing vodka, gin, and other flavored spirits where the other ingredients dictate the flavor profile.

It's crucial for students to grasp that neutral spirit production focuses on removing impurities and maintaining a high alcohol content. This is integral to the quality and versatility of the finished spirit for various uses in culinary, industrial, and alcoholic beverage productions.

Anhydrous Alcohol

Anhydrous alcohol, also known as absolute alcohol, takes purification a step further than rectified spirit. It has virtually no water content, hence the term 'anhydrous', which translates to 'without water'. With a purity of at least 99.5% ethanol by volume, it is the purest form of ethanol that can be commercially produced.

To produce anhydrous alcohol, rectified spirit undergoes additional processing such as chemical drying with agents like benzene or molecular sieves that absorb the remaining water. This is necessary because simple distillation cannot remove all the water due to the formation of a constant boiling mixture, or an azeotrope, between ethanol and water at around 95.6% ABV.

Understanding the concept of anhydrous alcohol is important for students as it highlights the complexities of achieving extreme purity in chemical substances. Anhydrous alcohol is used in applications where even minimal water content can cause interference, such as in the manufacturing of pharmaceuticals, laboratory use, and some specialty printing processes.