Formic acid – quite interesting two-functional connection representing not only carbonic acid, but also aldehyde. For this reason high-quality reaction to definition of this substance is very beautiful reaction of "a silver mirror", characteristic of aldehydes.
It is required to you
- Formic acid, 2% solution of nitrate of silver, 10% solution of sodium hydroxide, 5% ammonia solution, ideally clean test tube or flask, spirit-lamp or torch.
Instruction
1. Take a test tube, pour in it 2-3 ml of 2% of solution of nitrate of silver (AgNO3) and add to it one or two drops of 10% hydroxidesodiumof solution (caustic soda).
2. Carefully on one drop add 5% to the formed deposit solution of ammonia (NH3). So in your test tube ammoniac solution of oxide of silver, or a so-called reactant of Tollens - will appear [Ag(NH3) 2]OH.
3. Add 1 ml of solution of formic acid (HCOOH) to the received solution and carefully heat the received mix over a spirit-lamp or a torch.
4. If the checked substance really is formic acid, then walls of a test tube will become covered by a thin mirror layer of silver.
5. In the simplified look this high-quality reaction can be written down in the form of the following formula: HCOOH + Ag2O (ammoniac solution) = CO2 + H2O + 2Ag.