How do I prepare 70% ethanol from 96% ethanol (final volume is 500ml)?

Are you searching for ethanol basics and their preparation in different concentrations? This article explains all of that. 

What is Ethanol?

Before we jump into the topic of how to make 70 ethanol, let's first review the basics. Ethanol goes by many names, including ethyl alcohol, grain alcohol, EtOH, or simply alcohol with the formula CH₃CH₂OH. It is an extremely common compound used in industry and is frequently used in the production of various other industrial compounds, plastics and plasticizers, rubber and rubber accelerators, aerosols, mouthwash, soaps, cleaning supplies, polishes, pesticides, explosives, and veterinary medications. 

It can easily be made from a broad range of basic elements, some of which can be found in every nation that can support human habitation. These include waste organic products like straw, sawdust, molasses, water gas, industrial wastes like sulfite liquor from the pulp and paper sector, and more. Ethanol has been used as fuel recently and global demand for it is rising.

Preparation of Ethanol:

The most common ways to make ethanol are catalytic hydration of ethene and fermentation, the latter is more cost-effective since it is simpler and less expensive to make a large amount of ethanol from ethene. Back in the thirties, 75% of the total ethanol produced in the US was done through fermentation processes, and by 1968, over 90% was made by synthesis from catalytic hydration of ethylene. Starch fermentation is another method used to produce ethanol but the fermentation process and ethene compete with one another in terms of affordability and environmental sustainability.

What is 70 Ethanol?

One of the most common forms of Ethanol is 70% Ethanol which contains 30 percent of water in it. This type of ethanol is also a colorless liquid with a nice solvent/alcohol smell, is non-toxic, evaporates fast, and can easily catch fire. This concentration of ethanol is a great disinfectant for pipes, tiny surfaces, items, and unharmed human skin. Its disinfecting properties make it useful not just for skin hygiene but also for usage in dental offices, hospitals, and the food and animal feed industries.

This form of ethanol is believed by experts for its ability to better disinfect, even though you would assume the greater concentration is more effective. Its higher water content makes it easier to dissolve slowly, enter cells, and eradicate germs more effectively.

How to make 70 ethanol

To make this type of from 100 percent ethanol (absolute alcohol), you have to go back to chemistry basics where we studied the dilution formula i.e. (C1) (V1) = (C2) (V2). Here, C1 is the concentration of the starting solution whereas V1 is the volume of the starting solution. C2 and V2 are for the concentration and volume of the final solution. So, for the case of 70 Ethanol, C1 is the concentration of a provided solution (100%) and C2 is the concentration of a required solution (70%). By using the formula, we get 350ml of 100 percent concentrated ethanol. Remember that absolute alcohol is the anhydrous alcohol obtained after removing water completely from ethanol. It contains about 99.6% ethanol and is hygroscopic, meaning that it draws water. So, you shouldn't expect absolute ethanol to stay "100%" ethanol for very long if it is left open in the air.

Now, let us take an example of a provided solution of 96 ethanol concentration for 70 ethanol preparation. In this case, C1 is the concentration of a provided solution of 96% concentration and C2 is our desired concentration which is again 70%. In this case, for a volume of the final solution of 500ml, you need to have 365mL of 96% concentrated ethanol. It is recommended to leave it to cool and top it up with water again to bring the volume back to 1 liter as mixing both the water and ethanol produces a reaction that results in a reduced volume.

Wrapping Up:

To wrap up the topic of how to make 70 ethanol, it can be stated that common practices of producing ethanol are fermentation and catalytic hydration of ethene. However, the least expensive method of producing industrial ethanol is using petroleum-derived ethylene. The most common uses are decontamination and sterilizing. 70 ethanol is more effective than highly concentrated ones which can be easily made from 96% concentrated ones with the help of a dilution formula. 70 ethanol has a longer evaporation duration, which allows it to penetrate cells more effectively. Water at a 70% grade is also necessary for denaturing proteins.