250 years ago
1749 

• Pierre Joseph Macquer prepares yellow prussiate by the action of caustic soda on Prussian blue  

200 years ago
1799 

• Joseph Priestley prepares carbon monoxide in a pure state
• François Chaussier and Louis Nicolas Vauquelin  prepare sodium hydrosulphite, which can be used as an anti-chlorine agent  

150 years ago
1849 

• Henri Sainte-Claire-Deville prepares crystals of nitrogen pentoxide by the action of cooling the gas produced to -20°C
• Paul Daubrée  obtains crystalline tin oxide from tin chloride and water vapour in a red-hot porcelain tube
• Friedrich Wöhler  prepares metal nitrides directly from atmospheric nitrogen and metals by reduction of the oxides with carbon in air  

100 years ago
1899 

• Paul Walden uses liquid sulphur dioxide as a solvent for electrolytes and non-electrolytes
• Ernst Cohen  researches the meta-stable state of metals and metalloids
• Henri Moissan  prepares calcium phosphide and calcium arsenide from calcium in an electric melt-furnace
• Henri Moissan  and Paul Lebau  prepares gaseous sulphur hexafluoride (from fluorine and sulphur). At -55 °C this becomes a crystalline solid
• Herewith they demonstrate that sulphur has also a valency of 6
• Adolph Frank  prepares graphite by the action of carbon mono- or dioxide on metal carbides at high temperature  

50 years ago
1949   

• C Grube et al. prepare aluminium suboxide, Al_²0