45, CORNHILL, B.C., AND 122, REGENT STREET, W., LONDON. 113 



in excess during disturbed electrical weather, and in a deficiency during calm 

 and settled periods. We cannot lay too great a stress on the fact that where 

 different kinds of ozone tests are made use of by different observers, no 

 uniformity in results can be attained. Having this in view, we have prepared 

 our ozone tests (see No. 157) on a formula, by which we can obtain uniformity 

 in the indication and results that can be compared no matter how far the 

 stations may be removed from one another. It is important to note this, as we 

 often receive complaint of the failure of other Ozone Test Papers. It is recom- 

 mended to take observations every twelve hours where practicable, as there is 

 a marked difference in the amount of ozone registered in the day and night. 



APPARATUS FOR PRODUCING OZONE. 



A simple method of producing Ozone is passing sparks from an Electrical 

 Machine through a confined portion of Air in a glass vessel. 



154. Ozone Tube. A convenient form of apparatus for the production of 

 Ozone. It consists of a glass tube about j of an inch diameter, and five or six 

 inches in length, coated outside with tinfoil and enclosed in an outer tube, also 

 covered outside with tinfoil. These tubes are so arranged that the intervening 

 space between the tubes shall be as small as possible; the coating of the 

 inner tube being put into connection with the terminal of the secondary coil of 

 an inductorium, and the outer coating connected with the other terminal of the 

 same coil. The apparatus forms, in fact, a kind of Leyden Jar, and air or 

 oxygen passing between the tubes when the coil is in action becomes very 

 strongly ozonised. The air to be operated on is either to be drawn or forced 

 through the apparatus by the aid and use of an Aspirator or Gasometer. 



Price for the above, conveniently mounted . . .150 



155. Ozone may also be made by passing a current of dry air or oxygen 

 from a gasometer through a narrow glass tube, bent for convenience like the 

 letter U, about three feet in length, and containing a platinum wire two feet in 

 length, inserted into the interior of the tube, and one end of which communi- 

 cated with the outside through the wall of the tube. Round the whole external 

 surface of this U-shaped tube a spiral of copper wire is to be coiled, and an 

 induction current (from a coil giving half-inch sparks), is to be passed between 

 the external copper to the internal platinum wire, so as to have the platinum 

 wire as the negative pole in the interior of the glass tube. After a stream 

 of gas is ozonised by the transmission of the induction-current, it is to be 

 washed by passing it through a bulb tube containing caustic potash, when air 

 is employed ; or water, when pure oxygen is used ; in order to eliminate any 

 traces of nitrous and nitric acids that may have been formed. By means of 

 a gasometer the volume of gas passing through the tube may be exactly 

 ascertained. 



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