200 PKINCIPLES OF CHEMISTRY 



exterior of the tube a and the interior of the tube b c are coated with 

 tinfoil and connected with the poles of a source of electricity (with the 

 terminals of a Ruhmkorff's coil). A silent discharge passes through the 

 thin walls of the glass cylinders a and b c over all their surfaces, and 

 consequently, if oxygen be passed through the apparatus by the tube d, 

 fused into the side of , it will be ozonised in the annular space between 

 a and b c. The ozonised oxygen escapes by the tube e, and may be 

 introduced into any other apparatus. 5 



The properties of ozone obtained by such a method'' distinguish it 

 in many respects from oxygen. Ozone very rapidly decolorises indigo, 

 litmus, and many other dyes by oxidising them. Silver is oxidised by 

 it at the ordinary temperature, whilst oxygen is not able to oxidise 

 silver even at high temperatures ; a bright silver plate rapidly turns 



nitrogen, which are partially formed when air is acted on. It is remarked that at low 

 temperatures ozone is formed in large quantities. As ozone is acted on by corks and 

 india-rubber, the apparatus should be made entirely of glass. With a powerful Ruhmkorff 

 coil and forty tubes the ozonation is so powerful that the gas, when passed through a, 

 solution of iodide of potassium, not only sets the iodine free, but even oxidises it into 

 potassium iodate, so that in five minutes the gas-conducting tube is choked up with 

 crystals of the insoluble iodate. 



5 In order to connect the ozoniser with any other apparatus it is impossible to make 

 use of india-rubber, mercury, or cements, etc., because they are themselves acted on by, 

 and act on, ozone. All connections must, as was first proposed by Brodie, be hermetically 

 closed by sulphuric acid, which is not acted on by ozone. Thus, a cork is passed over 

 the vertical end of a tube, over which a wide tube passes so that the end of the first tube 

 protrudes aboA'e the cork ; mercury is first poured over the cork (to prevent its being 

 acted on by the sulphuric acid), and then sulphuric acid is poured over the mercury. 

 The protruding end of the first tube is covered by the lower end of a third tube immersed 

 in the sulphuric acid. 



6 The above-described method is the only one which has been well investigated. The 

 admixture of nitrogen, or even of hydrogen, and especially of silicon fluoride, appears to 

 aid the formation and preservation of ozone. Amongst other methods for preparing 

 ozone we may mention the following : 1. In the action of oxygen on phosphorus at the 

 ordinary temperature a portion of the oxygen is converted into ozone. At the ordinary 

 temperature a stick of phosphorus, partially immersed in water and partially in air in a 

 large glass vessel, causes the air to acquire the odour of ozone. It must further be 

 remarked that if the air be left for long in contact with the phosphorus, or without the 

 presence of water, the ozone formed is destroyed by the phosphorus. 2. By the action 

 of sulphuric acid on peroxide of barium. If the latter be covered with strong sulphuric 

 acid (the acid, if diluted with only one-tenth of water, does not give ozone), then at a low 

 temperature the oxygen evolved contains ozone, and in much greater quantities than 

 that in which ozone is obtained by the action of electric sparks or phosphorus. 3. Ozone 

 may also be obtained by decomposing strong sulphuric- acid by potassium inanimate, 

 especially with the addition of barium peroxide. Gorup-Besanez stated (but it requires 

 confirmation) that ozone is formed in the slow evaporation of large quantities of water. 

 In the near proximity of salt-gardens (salterns) the atmosphere is considerably richer in 

 ozone than in the surrounding neighbourhood. In connection with this is the fact that 

 the air of the sea-shore is rich in ozone. Ozone is also stated to be formed in the 

 ordinary process of the respiration of plants. This is, however, denied by many to be 

 the case. 



