Interesting reactions

Sodium Sulfite

Sodium sulfite can be prepared

1. By reacting sodium carbonate with sulfurous acid:

Na2CO3 + H2SO3 → Na2SO3 + CO2 + H2O

2. By reacting sodium hydroxide with sulfur dioxide gas:

2 NaOH + SO2 → Na2SO3 + H2O

3. By reacting metabisulfite with sodium hydroxide:

Na2S2O5 +2NaOH -> 2Na2SO3 +H2O

Sodium Thiosulfate

Sodium Thiosulfate may be prepared, can be read here for instance* 

1. By boiling a solution of sodium sulfite with Sulfur

Na2SO3 + 1/8 S8 → Na2S2O3

* -  There is a mistake there, they mention sulfate but it is sulfite, sulfate is Na2SO4 and not Na2SO3

Ammonia

1. By reacting sodium hydroxide with ammonium sulfate:

2NaOH + (NH4)2SO4 ---> Na2SO4 + 2NH3 + 2H2O

Ammonium sulphate is easier to find in agriculture shops. At low temperature the sodium sulfate will cristalyze and the remaining liquid is a solution of ammonia that may be used as fixer. You may also use ammonia directly, if you can buy it.

Sodium Carbonate

1. By reacting sodium bicarbonate with sodium hydroxide:
   
   NaHCO3 + NaOH → Na2CO3 + H2O
2. By heating sodium bicarbonate above 70ºC, faster at 200ºC
   
   2 NaHCO3 → Na2CO3 + H2O + CO2

Sodium Ascorbate

1. By reacting ascorbic acid with sodium hydroxide:
   
   C6H8O6 + NaOH = NaC6H7O6 + H2O
   
2. By reacting ascorbic acid with sodium carbonate:
   
   2 C6H8O6 + Na2CO3 = 2 NaC6H7O6 + CO2 + H2O
   
3. By reacting ascorbic acid with sodium bicarbonate:
   
   C6H8O6 + NaHCO3 = NaC6H7O6 + CO2 + H2O
   
4. By reacting ascorbic acid with sodium sulfite
   
   2 C6H8O6 + Na2SO3 = 2 C6H7O6Na + H2O + SO2