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Saturday, June 29, 2013
Sunday, June 16, 2013
Methanol and the Home-Brewer
In June 2013, a young man in Queensland died as a result of drinking homemade liquor. It is believed that the liquor contained a toxic level of methanol (also known as wood alcohol). Drinking 10 mL of pure methanol can cause permanent blindness, drinking 30 mL of methanol can kill you.
The first step in the production of homemade liquors, is the fermentation of sugar.
Methanol, CH3OH,is formed during fermentation.
When fermenting 6 kg of sugar dissolved in water for the production of distilled spirits such as whiskey or vodka, the home-brewer (and home-distiller) will typically find that the concentration of methanol in their brew is about 3 parts per million.
Many fruits are used by the home-brewer as the source of sugar to be fermented. Each fruit will lend a distinctive flavour to the final product. But fruits that are high in pectin will produce greater concentrations of methanol. Apples, apricots, guavas, quinces, plums, gooseberries, and citrus fruits like oranges, all contain high levels of pectin, typically more than 1% by mass pectin. Grapes, cherries and strawberries contain low levels of pectin, less than 1% by mass pectin.
Pectin contains galacturonic acid which has the structural formula shown below:
In pectin, about 80% of the carboxyl groups in galacturonic acid are esterified with methanol. The remaining non-esterified carboxyl groups exist as the acid, or as salts with sodium, potassium or calcium. When pectin is broken down by enzymes during the brewing process, the methyl esters react with water to produce methanol.
The second step in the production of homemade liquor is the distillation step.
This is the crucial step in removing as much of the toxic methanol as possible.
The boiling point of methanol is about 65oC, but the boiling point of ethanol (the desired product) is about 78oC. During the distillation process, the first fraction collected should contain the methanol. This fraction should be collected and discarded. The next fraction should contain the desired liquor. It is highly recommended that any distillate collected after about 96oC also be discarded.
Reference:
http://www.couriermail.com.au/news/queensland/ballandean-man-bill-lynam-who-lost-his-son-joel-to-homemade-liquor-poisoning-is-thankful-that-other-son-joshua-survived/story-fnihsrf2-1226664893229
Further Reading
http://ausetute.com.au/members/alkanolp.html (members only tutorial on alkanols)
http://ausetute.com.au/members/carboxyl.html (members only tutorial on alkanoic acids)
http://ausetute.com.au/partspm.html
http://ausetute.com.au/density.html
Suggested Study Questions:
The first step in the production of homemade liquors, is the fermentation of sugar.
Methanol, CH3OH,is formed during fermentation.
When fermenting 6 kg of sugar dissolved in water for the production of distilled spirits such as whiskey or vodka, the home-brewer (and home-distiller) will typically find that the concentration of methanol in their brew is about 3 parts per million.
Many fruits are used by the home-brewer as the source of sugar to be fermented. Each fruit will lend a distinctive flavour to the final product. But fruits that are high in pectin will produce greater concentrations of methanol. Apples, apricots, guavas, quinces, plums, gooseberries, and citrus fruits like oranges, all contain high levels of pectin, typically more than 1% by mass pectin. Grapes, cherries and strawberries contain low levels of pectin, less than 1% by mass pectin.
Pectin contains galacturonic acid which has the structural formula shown below:
The second step in the production of homemade liquor is the distillation step.
This is the crucial step in removing as much of the toxic methanol as possible.
The boiling point of methanol is about 65oC, but the boiling point of ethanol (the desired product) is about 78oC. During the distillation process, the first fraction collected should contain the methanol. This fraction should be collected and discarded. The next fraction should contain the desired liquor. It is highly recommended that any distillate collected after about 96oC also be discarded.
Reference:
http://www.couriermail.com.au/news/queensland/ballandean-man-bill-lynam-who-lost-his-son-joel-to-homemade-liquor-poisoning-is-thankful-that-other-son-joshua-survived/story-fnihsrf2-1226664893229
Further Reading
http://ausetute.com.au/members/alkanolp.html (members only tutorial on alkanols)
http://ausetute.com.au/members/carboxyl.html (members only tutorial on alkanoic acids)
http://ausetute.com.au/partspm.html
http://ausetute.com.au/density.html
Suggested Study Questions:
- Draw the structural formula for methanol.
- Locate the functional group present in methanol on the structural formula above. Name the functional group.
- At 25oC methanol has a density of 0.79 g mL-3. Calculate the mass of methanol present in a lethal dose of pure methanol .
- Convert the concentration of methanol given for homemade whiskey into a concentration in g mL-1.
- Assume the young man who died drank homemade whiskey. What minimum volume of homemade whiskey did he drink?
- For galacturonic acid given the:
- molecular formula
- molar mass
- On the structural formula for galacturonic acid identify and name the functional groups present.
- Draw the structure for the sodium salt of galacturonic acid.
- Draw the structure for galacturonic acid esterified with methanol.
- Give the molecular formula and molar mass for the structure above.
- Apples contain about 1% by mass pectin. 10 kg of apples are to be used in the production of a homemade liquor. What mass of pectin will be present?
- Assume exactly 100% of the carboxyl groups in galacturonic acid are esterified with methanol. How many moles of the ester are present in 10 kg of apples?
- Write an equation representing the reaction between this ester and water to form methanol and galacturonic acid.
- How many moles of methanol could be produced by the break down of pectin in 10 kg of apples?
- Assuming the young man who died had drunk this apple concoction without distilling and removing the methanol, what minimum volume of fermented apple-drink would he have had to have drunk?
- Why do you think most countries have outlawed home-distilling?
Friday, June 7, 2013
AUS-e-NEWS June 2013
Have you ever noticed that the price of E10 fuel, also known as gasohol, is less than the price of petrol (gasoline) ?
Just today, when I went to put fuel into my car, the price
for standard unleaded petrol (ULP) was 130.6 cents per litre while the price of
E10 fuel was 128.4 cents per litre.
Will using E10 instead of ULP save me money?
Read the June 2013 edition of AUS-e-NEWS to find out!
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