Sodium carbonate (Na2CO3) can be used for many chemical purposes; one of the most useful is for titrating acids. However sodium carbonate absorbs moisture, so it has to be standardised itself. It may also be expensive, and washing soda (which is Na2CO3) may have unwanted additives &c.
Fortunately, sodium carbonate can be synthesised from the much cheaper chemical sodium bicarbonate (NaHCO3), which only costs $1.59 for 500g. Some of the weight is lost as CO2 gas (I obtained a yield of 63%, which corresponds to a cost of about $2.52 for 500g of Na2CO3). The theoretical mass loss is 63.08%. I used an evaporating dish, and stirred the powder every so often with a wood paddle pop stick (can’t use metal or plastic!).
Initially, I put the sodium bicarbonate in the oven for 1 hour at 100°C, which only lost 10.8% of its mass. But after another 1 1/2 hours in the oven at 120-180°C, I obtained a yield of 62.94%, which is very close to the theoretical 63.08%, suggesting what remains is pure Na2CO3.
It wasn’t very difficult to conduct this experiment; it just needs sporadic attention over a 2 or 3 hour period.