Experiment 13: Iodoform test Flashcards
What must first be done to the solution in order for it to be used in the iodoform test?
The solution must be filtered to remove the yeast cells
What is done to the filtrate of the solution during the iodoform test?
The filtrate is added to a test tube
What is then added to the test tube containing the filtrate?
An equal amount of potassium iodide solution is added
What colour is potassium iodide when added to the filtrate?
It is a clear solution
What is added to the test tube of potassium iodide and filtrate during the iodoform test?
Sodium hypochlorite solution is added
What colour is the sodium hypochlorite solution and what does it do to the colour of the solution in the test tube?
It is a brown-orange colour but turns to solution it the test tube colourless
After all of the chemicals have been added to the test tube what is the next step of the iodoform test?
The test tube is placed in a water bath at 50-60 degrees Celsius for 4 to 5 minutes
What is done to the test tube after it has been in the water bath for 4-5 minutes at 50-60 degrees?
It is removed from the water bath and allowed to cool
What has formed within the test tube after being in the water bath if ethanol is present?
Pale yellow iodoform crystals have formed within the test tube
What does the presence of iodoform crystals in the test tube indicate?
It indicates the presence of ethanol
What control should be used for this experiment?
Water should be used instead of the filtered solution (crystals will not form)
What is the general test for alcohol (not specific to ethanol)?
Acidified potassium dichromate is added to the filtered solution and is then placed in a water bath, in the presence of alcohol the colour changes from orange to green
What is the iodoform test used for?
To check for the presence of ethanol (type of alcohol produced by yeast)
