Schonbein found that ozonised oxygen passed through a glass tube heated to 400°, loses its smell and action on potassium iodide, and the gas then appears to be ordinary oxygen.
Expt. 5. - Attach a piece of hard glass tube by a cork joint to the ozoniser, and heat the tube with a Bunsen flame. The issuing gas no longer acts on KI-starch paper. On allowing the tube to cool the reaction appears again. Marignac and de la Rive (1845) and Shenstone and Cundall (1887), found that pure dry oxygen can be ozonised by an electric discharge. Briner and Durand (1907) converted a confined volume of oxygen completely into a blue liquid mixture of ozone and oxygen by the silent discharge in a tube of dry oxygen, cooled in liquid air. Thus, ozone is merely a modification of oxygen.
This conclusion was also reached by Andrews (1856), who dried electrolytic oxygen by means of sulphuric acid and then passed it through two bulb-tubes,
 | Fig: Andrews experiments on ozone |
A containing potassium iodide solution, and B concentrated sulphuric acid. The increase in weight of the two bulbs was exactly equal to the oxygen equivalent (O = I2) of the iodine liberated. The bulb A was then replaced by a glass tube heated to 400°. The weight of the bulb B remained constant, showing that the gas contained no hydrogen. Andrews also found that ozone prepared in different ways (electric discharge, electrolysis, autoxidation of phosphorus) has the same properties.
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