Noah Vinter
Diluting 91% alcohol to 70% alcohol is a common practice for those looking to create a disinfectant solution, particularly for COVID-19. Diluting alcohol in this way can also be a cost-saving exercise, as 91% alcohol is often cheaper per ounce than pre-diluted 70% alcohol. To dilute 91% alcohol to 70%, you will need to perform a calculation to determine how much water to add. This calculation depends on the volume of the original 91% alcohol solution.
| Characteristics | Values |
|---|---|
| Alcohol Type | Isopropyl Alcohol |
| Initial Alcohol Concentration | 91% |
| Target Alcohol Concentration | 70% |
| Formula for Dilution | W = (0.91 * R) / 0.7) - R, where R = original volume of 91% alcohol, and W = volume of water to be added |
| Example Calculation | For 6.7 ounces of 91% alcohol, add (0.91 * 6.7) / 0.7) - 6.7 ounces of water, which is approximately 2.01 ounces of water |
| Alternative Method | Mix equal parts of 50% and 91% alcohol for an approximate 70% solution |
| Purpose | Increased effectiveness against viruses and bacteria due to evaporative properties, commonly used for disinfection and sanitization |
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What You'll Learn
Use distilled water to dilute 91% alcohol to 70%
To turn 91% alcohol into 70% alcohol, you need to dilute it with distilled water. This is because 70% alcohol is generally more effective at killing bacteria, viruses, and fungi on surfaces as the water content helps alcohol penetrate cell walls and denature proteins more thoroughly.
Firstly, you need to decide how much 70% alcohol you want to end up with. For example, if you want to make 1 litre of 70% alcohol, you would need to measure out approximately 292.93ml of distilled water and 707.07ml of 99% alcohol.
The formula for working out how much water to add is: W = (0.91 x R) / 0.7) - R, where W is the amount of water and R is the amount of 91% alcohol.
For example, if you have 6.7 ounces of 91% alcohol, you would need to add 2.01 ounces of water to get 70% alcohol. This is because 0.91 x 6.7 ounces = 6.097 ounces of pure alcohol. You then need to work out 6.097 = 0.7 x, which means x = 8.71. Therefore, you need to add 8.71 - 6.7 = 2.01 ounces of water.
It is important to note that you should always use distilled water rather than tap water when diluting alcohol as tap water contains minerals, salts, and potentially microbes or chlorine, which can leave residue, interfere with cleaning/disinfection, or slightly alter the solution's properties.
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Mix 7 parts 91% alcohol with 3 parts water
To turn 91% alcohol into 70% alcohol, you will need to dilute it with water. This process is called alcohol contraction.
Firstly, you need to calculate how much pure alcohol you have. If you have 6.7 fluid ounces of 91% alcohol, then you have 6.097 ounces of pure alcohol. To get this number, you multiply 0.91 by 6.7 ounces.
Next, you need to calculate how much water to add to get a solution with 70% alcohol. Using the formula W = (0.91 x R) / 0.7) - R, where W is the amount of water and R is the amount of original alcohol, you can calculate that you need to add 2.01 ounces of water.
Alternatively, you can use the ratio of 7 parts 91% alcohol to 3 parts water to get a solution of 70% alcohol. This means for every 7 parts of 91% alcohol, you add 3 parts water. So, for 6.097 ounces of pure alcohol, you would need to add 2.613 ounces of water.
It is important to note that the final volume of the solution may be slightly less than the sum of the volumes of alcohol and water due to the alcohol molecules fitting between the water molecules.
As an example calculation, if you have 16 ounces of 91% alcohol, you would need to add 4.8 ounces of distilled water to get a solution of 70% alcohol.
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77% 91% alcohol and 23% distilled water makes 70% solution
To turn 91% alcohol into a 70% solution, you need to dilute it with distilled water.
The formula for this dilution is:
> R = original oz of 91% alcohol
> W = oz of water to add to get 70% alcohol
> W = (0.91 x R) / 0.7) - R
Using this formula, you can calculate the amount of water needed to dilute the 91% alcohol to your desired volume of 70% alcohol.
For example, let's say you have 6.7 ounces of 91% alcohol and want to end up with a total of 8.71 ounces of 70% alcohol solution.
First, calculate the amount of pure alcohol in the original solution:
91 x 6.7 ounces = 6.097 ounces of pure alcohol
Next, determine how much alcohol you want in your final solution:
097 ounces = 0.7 x 8.71 ounces
Therefore, to get a total volume of 8.71 ounces at 70%, you need to add 2.01 ounces of distilled water to your original 6.7 ounces of 91% alcohol.
This calculation assumes that the volume remains constant when mixing alcohol and water, which may not be entirely accurate due to differences in the molecular structures of the two substances.
Another way to approach this dilution is to use the alcohol dilution calculator available on some websites. These calculators can help you determine the amount of alcohol and water needed for your desired solution.
It's important to note that the above calculations and formulas are based on specific gravity and percentage by volume. The final volume of the diluted solution may vary slightly due to the different molecular structures of alcohol and water.
In summary, to make a 70% alcohol solution from 91% alcohol, you need to dilute it with distilled water. The amount of water needed depends on the volume of 91% alcohol you start with and the desired volume of the 70% solution. Using the provided formula or online calculators, you can determine the exact amount of water to add for accurate dilution.
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Mix equal parts 50% and 91% alcohol for 70% solution
To turn 91% alcohol into a 70% solution, you will need to dilute it with water. This can be done by mixing equal parts 50% and 91% alcohol to create a 70% solution.
Firstly, it is important to understand that a 70% alcohol solution is more effective at killing germs than a stronger concentration. This is because microbial cells rely on their membrane integrity for survival. When an alcohol solution is too concentrated, it can rapidly coagulate proteins on the microbe's outer membrane, effectively sealing the microbe instead of fully penetrating it. A 70% solution, on the other hand, includes enough water to facilitate a slower, more thorough penetration of the cell membrane, resulting in total protein coagulation inside the cell and a more complete kill.
Now, to create a 70% solution by mixing equal parts 50% and 91% alcohol, you will need to understand some basic mathematics. Let's say you have 100ml of 50% alcohol and 100ml of 91% alcohol. To get the volume of pure alcohol in the 50% solution, multiply the volume by the percentage: 100 x 0.50 = 50ml. For the 91% solution, the calculation is: 100 x 0.91 = 91ml. Adding these two amounts of pure alcohol together gives you 141ml. To find out how much water you have in the 50% solution, subtract the pure alcohol volume from the total volume: 100 - 50 = 50ml.
So, when you mix the two solutions together, you have 141ml of pure alcohol and 50ml of water, giving you a total volume of 191ml. This is a 70% alcohol solution because the volume of pure alcohol (141ml) makes up 70% of the total volume (191ml).
It is important to note that this process assumes you are working with percentages by volume and that the volumes add up when solutions are created from pure substances.
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70% alcohol is more effective against viruses/bacteria than 91%
To turn 91% alcohol into 70% alcohol, you need to dilute it with water. The exact amount of water needed depends on the volume of alcohol you start with. For example, if you have 6.7 ounces of 91% alcohol, you would need to add 2.01 ounces of water to get a 70% alcohol solution. This can be calculated using the formula: W = (0.91 x R) / 0.7) - R, where W is the amount of water and R is the amount of 91% alcohol.
Now, let's discuss why 70% alcohol is more effective against viruses and bacteria than 91% alcohol. Firstly, 70% alcohol has been found to be the most effective concentration for killing microbes. Higher concentrations, like 91%, are less active against certain organisms. This is because 70% alcohol has the right balance of alcohol and water, which allows it to dissolve lipids and denature proteins in bacteria and viruses, disrupting their structure and rendering them inactive.
Additionally, 70% alcohol evaporates at a slower rate compared to higher concentrations. This is advantageous because it gives the alcohol sufficient contact time with the surface or organism being treated, increasing its effectiveness as a disinfectant.
The antimicrobial activity of alcohols is generally considered optimal when the concentration is between 60% and 90%. While 91% alcohol can be highly effective in certain applications, such as industrial or medical settings where a fast-acting solvent is required, it may evaporate too quickly in other contexts, reducing its ability to kill all pathogens.
Therefore, 70% alcohol is often recommended for household and consumer applications, as well as in the healthcare industry, due to its effectiveness against a wide range of bacteria, fungi, and viruses, combined with its slower evaporation rate, making it a safer and more practical option for general use.
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Frequently asked questions
A 70% alcohol solution is more effective against viruses and bacteria due to its evaporative properties. It is also less harsh on the skin and certain plastics and coatings.
One easy way to dilute 91% alcohol to 70% is to mix equal parts of 50% and 91% alcohol. This will give you a solution that is approximately 70% alcohol.
To dilute 91% alcohol to 70% alcohol using water, you can use the formula R = original ounces of 91% alcohol and W = ounces of water to add to get 70% alcohol. W = (0.91 x R) / 0.7) - R. For example, if you have 6.7 ounces of 91% alcohol, you will need to add 2.01 ounces of water.
Always add the more concentrated liquid (91% alcohol) slowly to the less concentrated one (water) to control potential reactions or heat release. Use distilled or deionized water to minimize impurities.
Use a glass or chemical-resistant plastic container for mixing. Transfer the final 70% solution to an amber glass or HDPE plastic bottle for storage.
