This is just the Tollen's test for reducing sugars on a large scale
but the resulting silvered flask is most impressive.
The quantities here that we're going to use are appropriate for a one or two litre,
one or two cubic decimetre, flask but they can be scaled up or down as appropriate.
The most important thing to remember about this experiment
is the flask must be scrupulously clean if we are to get a good silver mirror.
The best procedure is to clean it with detergent
and a brush, rinse it out with water
followed by concentrated nitric acid and several rinses with distilled or deionised water.
We start with 150 cubic centimeters of 0.1 moles per cubic decimetre silver nitrate solution.
We add to this a drop at a time some 880 ammonia.
We get a brown precipitate first,
which, on adding more ammonia, will eventually redissolve, to give a clear solution.
It'll take about five cubic centimetres of 880 ammonia.
We now take 75 cubic centimetres of 0.8 moles per cubic decimetre potassium hydroxide
Again we get a brown precipitate of silver oxide.
And we add more 880 ammonia to this a drop at a time
again until the precipitate redissolves to give a clear solution.
This solution is ammoniacal silver nitrate.
It contains silver plus ions complexed with ammonia molecules.
We now put the ammoniacal silver nitrate
into the flask we're going to silver
and add to it 12 cubic centimetres of 0.25 moles per cubic decimetre glucose solution.
Glucose is a reducing sugar
and will reduce the silver ions to metallic silver.
The solution will start to go brown or grey
and at this point it's important to keep moving the solution around the flask
so that the whole of the inside of the flask
is constantly being wetted.
Over a period of a couple of minutes
a silver mirror will begin to form on the inside of the flask.
I stress it's vital to keep the solution moving around so that the whole of the inside of the flask
is exposed to the silvering solution.
The chemistry of this process was actually used in the past
to form the silver coating on mirrors, looking glasses.
A giant Christmas tree decoration.
When you finish this demonstration
it's important to dispose of the spent ammoniacal silver nitrate solution as quickly as possible.
You should do this by pouring it down the sink and flushing it with plenty of water.
Ammoniacal silver solutions have been known to explode
if they are left standing for some considerable time, for example overnight.
Therefore it's vital not to put the residues in a silver residue container.
For the same reason it's not appropriate to make up the ammoniacal silver nitrate solution
any considerable time before the demonstration
and certainly not the previous day for example.