If I Could I Wood … A Destructive Distillation Lab

All the energy that we use in our everyday lives, namely, electricity, cooking gas, petrol, are generated from substances that may be termed as fuels. Fuels are those substances that when oxidized give rise to heat energy. This heat energy can be converted to other forms of energy like electricity or mechanical energy like vehicle motion. Even the food we consume can be termed as fuel, as it is converted in our body to give us energy to sustain, breathe, walk, have our hearts beating, brains functioning, Thus fuels form a very basic and important component in our lives.

Distillation is a process used to separate the substances composing a mixture. It involves changes of phase only. Today, refined methods of distillation are used in many industries, including the alcohol and petroleum industries.

A simple distillation apparatus consists essentially of three parts: a vessel (such as a flask or test tube) from which the vapor is emitted, a condenserand a receiving vessel (such as a flask or test tube) in which the condensed vapor is collected. The mixture that is to be distilled is placed in a vessel and heated. The substance with the lowest boiling point vaporizes first; the temperature remains constant until that substance has completely distilled. The vapor is led into the condenser where, upon being cooled, it condenses into a liquid and runs off into a receiving vessel. The liquid product obtained is known as the distillate. Those substances having a higher boiling point remain in the flask and constitute the residue.

When the substance with the lowest boiling point has been removed, the temperature can be raised and the distillation process repeated with the substance having the next lowest boiling point. The process of obtaining portions (or fractions) in this way is fractional distillation. Fractional distillation is commonly used in refining petroleum, some of the fractions thus obtained being gasoline, benzene, kerosene, fuel oils, lubricating oils, and paraffin.

Another form of distillation involves heating (out of free contact with air) such substances as coal, oil and shale and collecting separately the portions driven off; this is known as destructive distillation. Coal, for example, yields coal gas, coal tar, and ammonia. Ammonia is also obtained by the destructive distillation of oil shale.

Wood gas, produced by the destructive distillation of wood, is a combination of many inflammable gaseous hydrocarbons, but is mainly methane. As the wood is heated further, you will notice a black liquid deposit collecting at the bottom of the water. This is called coal tar. If you smell the water, you will get a distinct odor of acetic acid and methyl alcohol. The destructive distillation is complete when the first test tube has only black residue left in place of the wooden splints. This is called charcoal. Thus destructive distillation of wood gives wood gas, tar, methyl alcohol, acetic acid, water and charcoal. Destructive distillation was used in the past for generating methyl alcohol, which is used today in windshield washer solvent and many other applications.

Materials

1 2-hole stopper / 1 sm 1-hole stopper / Gloves
1 600 mL beaker / 1 sm stopper / Glycerin
1 gas collection bottle w/cap / 15 wood splints / Grease pen
1 large extra long test tube / 2 glass elbows / ice
1 large test tube / 2 ring stands / Matches
1 lg 1-hole stopper / 2 test tube clamps (1 with rubber sleeve, 1 without) / Red litmus paper
1 Meeker burner with gas tubing / 2 test tubes / striker
1 pneumonic trough / Blue litmus paper / Watch glass
1 rubber tubing / forceps

Data

Observations - Day 1
Step 7
Step 9
Step 12
Step 13
Step 15
Step 16
Observations - Day 2
Step 2
Step 3
Step 8
Step 11

DAY I:

  1. Put on gogglesapron.
  1. Smear glycerin on each end of the glass elbows. Insert the lubricated end of each elbow into the two-hole stopper using the inserter as shown below.
  1. Attach a one-hole stopper, using lubricant and the inserter, to the end that will be closest to the gas valve as shown below.
  1. Place 15 wooden splints (cut in half) into the bottom of the longest test tube.
  1. Fill a 600mL beaker three-quarters full with ice. Add water to fill to 500mL. Set up the apparatus as shown below using the large test tube in the beaker.
  1. Light Meeker burner and place directly under the splints. To prepare for the second apparatus set-up fill the pneumatic trough ¾ with water. The glass bottle also needs to be filled completely to the top. Make sure no air is left in the bottle.
  1. Immediately as gas is being released from the unattached end of the glass elbow (the exhaust port), immediately light a match to the end of the exhaust port. Record observations (color, smell, flammable…etc).
  1. Once observations have been recorded, attach rubber tubing as shown below. Use glycerin if needed. Teacher will demo the pneumatic trough set-up.
  1. Continue heating until glass bottle is full. Once full, cap with lid. Record observations (how long to fill jar, color, smell…etc).
  1. Label the jar with your lab station and period, using grease pencil, and place in fume hood.
  1. Continue heating splints for 5 minutes. If needed, move burner to ensure even heating of wood splints. Allow the gas to bubble into the pneumonic trough. GAS IS EXTREMELY FLAMMABLE! KEEP ALL OPEN FLAMES AWAY FROM GAS.
  1. Remove rubber tubing from exhaust port and once again light a match. Record observations.
  1. Turn off burner. Record observations about the material left in the distillation tube.
  1. Transfer distillate to the smallest test tube. Stopper the tube, label tube with group number and period using a grease pencil. Give to teacher to store.
  1. Examine the remains of the wood splints. Record observations.
  1. Try burning one of the charred splints over a watch glass. Record observations. Put burned wood splints in the waste container provided by the instructor. Do NOT put them in the trash can!
  1. CLEAN and WASH ALL MATERIALS! Wash each glass elbow and return to teacher. Points will be deducted for improper clean-up.

DAY II:

  1. Put on goggles apron.
  1. Pick up new glass elbow, clean test tube with pipet, and distillate from instructor. Do not shake the test tube with the distillate before observing. Record observations about the liquid in the condensing tube.
  1. Red Litmus paper turns blue in the presence of a base. Blue litmus paper turns red in the presence of an acid. Use pipet to remove a small sample from the distillate tube. Test the distillate with both red and blue litmus paper and record observations.
  1. Add 2 boiling chips into the distillate.
  1. Fill a 600mL beaker three-quarters full with ice. Add water to fill to 500mL.
  1. Attach a one-hole rubber stopper to a glass elbow using glycerin and an inserter. Attach the tubing to the free end of the glass elbow. Continue to assemble the apparatus as shown below.
  1. Light meeker burner and place under the distillate. Keep a LOW flame so that the distillate DOES NOT boil over into the glass elbow. Adjust the burner and/or remove the heat as needed.
  1. Heat distillate until approximately half has boiled off. Compare the liquid in the two test tubes. Record observations.
  1. Turn off burner. Allow distillate to cool. Remove rubber stopper, tubing, glass elbow.
  1. Remove cooled test tubes from clamps.
  1. Mix the distillate into the 2nd test tube and record observations.
  1. CLEAN and WASH ALL MATERIALS! Wash each glass elbow and return to teacher. Flush liquids down drain with copious amounts of water. Points will be deducted for improper clean-up.

Analysis Questions

  1. Do you think it is possible to get the wooden splints back by mixing all the stuff you have collected? Why or why not?
  1. Did the gas burn? Why do you suppose that this happened?
  1. When heating the 15 wood splints (Day 1, step 5), they did not catch on fire. Hypothesis why this happened.
  1. Were all of the distillates that were collected there all of the time, or were they formed by heating? Describe how you could prove your theory.