Clausius[3] at one time supposed that free atoms of oxygen might exist in an uncombined state, and his hypothesis on the nature of ozone was that this substance consisted of a mixture of molecules and free atoms of oxygen. In a later paper[4], however, he abandoned this view and regarded ozone as consisting of one or more atoms of oxygen feebly united, (lose verbunden) with molecules of ordinary oxygen.
The idea that a third form of oxygen existed also obtained support from the fact that certain organic substances when exposed to the light in the presence of oxygen or air, acquire oxidizing properties. In 1850 Schönbein[5] stated that ether turpentine, and oil of lemons if allowed to stand in diffused light in contact with the air acquires the power of decomposing potassium iodide, and decolorizing indigo. In a subsequent paper[6] he shows that methyl and ethyl alcohols, tartaric and citric acids and even sulphuretted and arsenuretted hydrogen in the presence of sun light can decolorize indigo. These studies led Schönbein to publish a theory on the different modifications of oxygen. In this paper[7] he states that besides ordinary oxygen there are two other conditions in which it may exist one of these is ozone, or positively electrified oxygen, the other _antozone_ or negatively electrified oxygen. The union of ozone and antozone gives ordinary oxygen. He also stated that antozone was formed by the action of light on turpentine and air, and subsequently in 1862[8] he claimed that antozone was identical with the gas obtained when barium superoxide is treated with acids. Meissner[9] also supported the views of Schönbein and claimed that antozone was formed in two ways:--1st, By treating barium dioxide with concentrated sulphuric acid, 2nd, By the electrification of oxygen; being produced simultaneously with the ozone.
These statements remained unquestioned for a number of years and are found in the text books of the period, (for example Graham-Otto, and Gorup-Besauez) but in 1870 Engler and Nasse[10] undertook a thorough investigation to determine whether antozone existed. By treating barium dioxide with strong sulphuric acid they find a gas to be given off which is a mixture of ozone and hydrogen dioxide, and they also show that the stronger the acid the greater the quantity of ozone produced. Secondly, Meissner had stated that by the electrification of oxygen ozone and antozone were formed. The evidence of the existence of antozone being this; when the ozonized oxygen was passed through a solution of potassium iodide to destroy the ozone, the residual gas gave white fumes when brought into contact with water, and after a time hydrogen dioxide could be detected in the water. Schönbein and Meissner held that the ozone having been destroyed by the potassium iodide the antozone passed on and oxidized the water to hydrogen dioxide. Now Engler and Nasse show that when ozone is decomposed by easily oxidisable substances in the presence of water hydrogen dioxide also is formed, and it was the vapor of this compound which had been regarded as antozone. It is known that ozone cannot oxidize water, but that it is to a slight extent oxidized when other oxidisable substances are present is not surprising, as other phenomena of a similar kind are known. Thus when nitric acid acts on an alloy of silver with gold or platinum, containing a certain proportion of silver, some of the gold or platinum are dissolved although by themselves they are insoluble. When ammonia burns some of the nitrogen as well as the hydrogen is oxidized. Engler and Nasse therefore conclude that there is no basis for the assumption of a third form of oxygen having the properties attributed to antozone.