Page:Text-book of Electrochemistry.djvu/324

 be calculated; these compounds follow exactly Ostwald's dilution law. This is also the case for the other salts whose conductivity is, therefore, proportional to the square root of the concentration. Two metal poles (of nickel, copper, iron, or platinum) placed in a flame containing such a vapour showed a potential difference which approximated to that which would be obtained in an aqueous solution. No polarisation could be observed, which is probably due to the strong " polar- isation current ; " quite the same observation is made with fused electrolytes and glowing oxides. For small electro- motive forces (up to 0*5 volt) the current strength is nearly proportional to this force, but it afterwards increases much more slowly, probably on account of an insufficiency of gaseous ions. Besides the electrolytic conduction, there is also a so-called convective condttction through the particles which become charged at one electrode and are discharged at the other. In the case of the salts of the alkaline earth metals this convective current is much greater than the electrolytic, and with other salts the electrolytic conduction in the Bunsen flame cannot be detected.

At the ordinary temperature gases assume an electrolytic conductivity under the influence of ultraviolet, Eontgen, or Becquerel rays. So far as the investigations on this subject go, it has been found that here, too, the laws of electro- motive effect between two metals, Ostwald's dilution law, etc., apply just as well as for electrolytes in solution. The electrolytic conductivity of gases is not yet of any practical interest.

Production of Ozone. — The production of ozone by the sUent electrical discharge is of practical importance. This substance is firequently found at the anode of an electrolytic bath. Thus, McLeod (^J) found that by working with an extremely high current density he obtained an anode gas containing up to 17'4 per cent, of ozone ; the anode consisted of a so-called Wollaston point, ie. a fine platinum wire fused into a glass tube so that only the end remained free. Traces of ozone are found in the arc light in which a number of gas

�� �