Making Chloroform


Historically chloroform was widely used
as an anesthetic but nowadays it’s mostly used just as a solvent. Interestingly it can be easily made from
common household products. In this experiment the major chemicals I used
were 3.6 liters of concentrated bleach and a hundred
milliliters of acetone. The first thing that must be done is to
determine the concentration of sodium hypochlorite in the bleach. This is done by reacting about five
milliliters of bleach with three percent hydrogen peroxide. As shown in the equation above the
hydrogen peroxide reacts with the sodium hypochlorite to form water, sodium
chloride and oxygen gas. Hydrogen peroxide is added until no more bubbling
occurs and the reaction is complete. The level of the water in the graduated
cylinder is measured before and after the addition of the gas. By calculating
the amount of gas that has evolved and on the assumption that one mole of gas
occupies a volume of 24 liters we can calculate the concentration of the
bleach. The equation that I used as shown above and the result I obtained was that
sodium hypochlorite concentration was about 1.28 molar. This isn’t necessary but I used the
hydrometer to measure the density of the bleach and I determine that the
concentration was about 8.6 percent. The bleach was chilled to about -2 degrees Celsius and a hundred and fifty milliliters was poured out. A
hundred and fifty milliliters is removed to make sure that it has enough space to
add the acetone as well as to shake it. The reaction of bleach with acetone is
extremely exothermic and it’s absolutely necessary to cool it to at least zero
degrees Celsius before the addition. I added about a hundred milliliters of
acetone to the bleach which represents an excess of bleach at around eleven
percent. I think an access between three to five percent is better and eleven
percent as much too high. Use an excess of bleach because we want to make sure that
all of the acetone is consumed. Any leftover acetone could form a difficult
to separate azeotrope with the chloroform. After adding the acetone the bottle is
capped and shaken. The cap is then removed in place lightly on top to allow
any gases to escape. I left the bottle overnight to allow for
a complete separation of the chloroform from the aqueous layer. Chloroform is
denser than water and immiscible so it should form a layer on the bottom.
After five minutes the temperature is already at around 30 degrees Celsius. The
temperature peaked at around 45 degrees Celsius. The purpose of the video I will visually
demonstrate the reaction between the acetone and the bleach. When the acetone
is added it reacts with three equivalents of sodium hypochlorite to
form chloroform, sodium hydroxide and sodium acetate. After allowing the solution to sit
undisturbed for a short period of time it’s possible to see chloroform in a
separate layer on the bottom. The solution is still yellow due to the
presence of unreacted sodium hypochlorite. Carefully decant the upper aqueous layer.
To the large amount of water you’re going to need to do this several times. You should empty the aqueous layer into
a waste container labeled bleach and chloroform waste. Eventually the remaining liquid of the
bleach bottle is poured into the beaker and the chloroform layers allowed to
settle on the bottom. You might notice that the solution is much less yellow in
the previous example that I showed. this This is because it was allowed to react
overnight and the concentration of sodium hypochlorite in the solution is
much less. Leave it for several minutes until the chloroform layer fully
separates. Decant off as much of the aqueous layer as possible and then add
the rest to a separatory funnel. Allow the two phases to separate and then
drain the lower chloroform layer. Add the upper aqueous layer to your waste
container. The chloroform was washed once with saturated sodium chloride and then
it was added to a distillation flask containing calcium chloride. The simple
distillation of the chloroform was carried out using a hot water bath. The distillate that came over below 60
degrees Celsius was cloudy and it was discarded. The temperature then remain constant at
around 60 degrees and the distilled was collected as a clear liquid. The total volume of chloroform obtained
was about 58 milliliters. The chloroform is transferred to a bottle
that was wrapped in tin foil to protect it from light. About 1 milliliter of absolute ethanol
was added to stabilize the chloroform and prevent the formation of phosgene.
Again the final yield was about fifty eight milliliters which represents a
final yield of about 53 percent.

Leave a Reply

Your email address will not be published. Required fields are marked *