how do you estimate carbon and hydrogen present in the organic compound by leibigs method
Answers
A known mass of organic compound is heated in the presence of pure oxygen. The carbon dioxide and water formed are collected and weighed. The percentages of carbon and hydrogen in the compound are calculated from the masses of carbon dioxide and water. Estimation of carbon and hydrogen in an organic compound is based on their conversion to CO, and H2O respectively. The percentage of carbon and hydrogen are calculated from the masses of CO2 and H2O.
The apparatus consists of a long glass tube. This is called combustion tube. To one end of this tube, a U-tube containing anhydrous calcium chloride and a bottle containing concentrated potassium hydroxide solution (caustic potash) are attached in series. These in turn, are connected to a guard tube containing anhydrous calcium chloride.
The combustion tube is packed with cupric oxide and copper guaze. The other end of the tube has a provision for passing oxygen. The combustion tube is heated in a furnace. The U-tube and the caustic potash bottle are weighed before the start of the experiment. The combustion tube is heated strongly in a current of pure and dry oxygen to remove moisture and C02 that may be present.
A known mass of the organic compound taken in a porcelain boat is placed in the combustion tube and strongly heated. The organic compound is oxidized by cupric oxide to C02 and HzO (Nitrogen, if present is also oxidized to oxides of nitrogen. These are reduced back to nitrogen by copper).
The combustion products first pass through the U-tube containing anhydrous calcium chloride (absorption of H20) and then through the caustic potash bottle (absorption of C02). The U-tube and the caustic potash bottle are weighed after cooling them to laboratory temperature.