LABORATORY WORK No 1

Performed by:

Zuzana Trestikova, Radka Vitkova

Conditions:

t = 17.1 °C; p = 1021.0 hPa; φ =  46.2 %

Topic:

Distillation of Fermented Fruit Juice

1.

Prepare fruit juice from ripe fruit.

2.

Separate ethanol from the fermented fruit juice by distillation.

3.

Determine the quantity of pure ethanol in 100 ml of fermented fruit juice.

4.

Count the percentage of ethanol in fermented fruit juice.

5.

Demonstrate the qualities of the extracted ethanol on burning its vapours.

7.

Pour the ethanol into a china bowl and light it. Put the test tube with 10 ml of water and with thermometer over the flames. Measure the time of burning and the temperature change of warmed up water.

a)

Determine the time of burning of the ethanol and the quantity of the liquid left after burning.

b)

Determine the change in temperature of the water, to which 100 ml of water warm up in the test tube during the ethanol burning.

c)

Count the amount of heat Q [J] that was absorbed by the heated water.

Theory:

In green parts of plants, the sugar C₆H₁₂O₆  and oxygen O₂  are developed from carbon dioxide CO₂ and water H₂O:

The sugar from ripe fruit changes in ethanol C₂H₅OH and carbon dioxide CO₂ under the influence of wine fermentation yeast plants:

During the fermentation of juice from various fruit (plums, apples, apricots etc.),  liquid ethanol C₂H₅OH and gaseous carbon dioxide CO₂ develop. Ethanol is separated from the remained stones, skins and water by distillation, that is a method of separating two liquids, the boiling temperature of which is different.

During the heating, the liquid with lower boiling temperature, i. e. ethanol (its boiling temperature is 85.5 ^oC) evaporates first. After all the ethanol had been evaporated, the temperature of the mixture starts to rise to the boiling point of the next liquid, i. e. water (100 °C).

During the burning of ethanol vapours, also the heat Q is being liberated:

The amount of heat received by the water is calculated as follows: Q = c . m . Dt,
where c [J/kgK] is the specific heat capacity of water, m [kg] is the water mass and Dt [⁰C] is the change of water temperature.

Aids:

Distilling retort with narrow exhaust tube, cooler,  two rubber hoses, thermometer, bowl, test tube, burner.

Procedure:

1.

Prepare ripe fruit, for example apricots. Put the pulpified fruit into the demijohn, cork it with a tightly fitting cork with fermentation tube and let it ferment by the temperature about 20 ⁰C for approximately 15 days. During the fermentation (transformation of sugar into ethanol and carbon dioxide) the developing carbon dioxide CO₂ is bubbling through the fermentation tube.

2.

After the initial stormy fermentation, decant the wine, i. e. separate the clear liquid from settlings. Let the wine cease fermenting.

3.

Pour 100 ml  of wine developed by fermenting of apricot juice in the distilling retort with narrow exhaust tube.  Put a tightly fitting cork with thermometer into the retort neck so that the globule of the thermometer is where the alcohol vapours leave for the cooler. Fix the cooler on the retort drainpipe. Let the cooling water flow into the cooler in a countercurrent way.

4.

Warm the retort slowly up, so that the temperature of vapours leaving for the cooler isn´t much above the boiling temperature of ethanol, i. e. 85.5 ⁰C.

5.

Observe the ethanol vapours in the cooler converting into liquid. Stop distilling when the temperature of  retort leaving vapours begins to rise to the boiling temperature of the next liquid, i. e. water (100 ⁰C).

6.

Measure the amount of distilled ethanol in graduated vessel.

7.

Pour the ethanol into a china bowl and light it. Put the test tube with 10 ml of water and with thermometer over the flames. Measure the time of burning and the temperature change of warmed up water.

Picture:

Measuring and calculation:

V₁ = 100 ml

= the initial volume of apricot juice

V₂ = 18 ml

= the distilled ethanol volume

p = 18 %

= number of per cent of ethanol in 100 ml of fermenting liquid

t₁ = 20 °C

= temperature of cold water in test tube before heating

t₂ = 90 °C

= final water temperature after heating it with burning ethanol

Δt = t₂ - t₁ = 70 °C

= change of water temperature in test tube

t = 300 s

= burning time of ethanol in china bow

Q = c . m . Δt
= 4186.8 x 0.010 x 70 J
= 2930.8 J = 2.9 kJ

= amount of heat received by water

Conclusion:

We destilled 18 ml of smelling ethanol, i. e. 18 %, from 100 ml of thick orange-coloured apricot juice. The temperature was  20 °C. After heating with burning ethanol that lasted about 300 s, the water temperature was 90 ^oC so that it was heated by  70 ^oC. The heat received by water from the burning ethanol was about 2.9 kJ.