158 Intelligence and Miscellaneous Articles, 



adjusting the ball and disk to a proper distance, a nebulous aigrette 

 surrounds the latter, quite filling the interval between it and the 

 wall of the tube, while the part of the tube between the disk and 

 ball is crowded with innumerable hazy streams converging upon the 

 positive pole, or simply causing the latter to be covered with a faint 

 glow. A current of air or oxygen sent into the tube must pass 

 through this, and ozone is very rapidly produced and in great quan- 

 tity. The condensers are of course not used with the machine when 

 this apparatus is employed. 



There appears to be an advantage in causing the oxygen to pass 

 from the negative toward the positive within the tube ; for the gas 

 through vi'hich the discharge passes is transported in tlie contrary 

 direction, as may be readily seen on bringing a candle-flame between 

 the poles of the machine, or causing a thin column of smoke to rise 

 through the polar interval. The flame and the smoke are deflected, 

 and stream off towards the negative pole. If the gas should be 

 admitted in the direction mentioned, there v/ould be a tendency to 

 obstruct its flow somewhat, and thus keep it longer under the 

 influence of the electricity. 



Some experiments which were made with the apparatus will give 

 an idea of its efficiency. One hundred cubic centimetres of water 

 were placed in an upright tube or test-glass, and into it were put 

 20 drops of strong indigo solution, causing it to assume a deep blue 

 tint. Air was driven through the ozonizing tube, under a pressure 

 of about three inches of water, and on issuing from it conveyed by 

 a tube into the solution. When the electro-machine was put in 

 operation, being turned with sufficient speed to give nearly its 

 maxim.um eff"ect, the solution completely lost its blue colour in less 

 than four minutes. Blue litmus solution, under similar circum- 

 stances, became pale pink, but required a considerably longer time 

 for the change. 



When Schonbein's test solution is employed, the deep blue colour 

 is immediately produced ; but the solution is too thick to work well 

 if the starch has been heated considerably, or for a long time, in 

 making it. A better proportion to take is one part of potassic iodide 

 by weight, ten parts of starch, and five thousand parts of water. 

 This forms a milky solution sufficiently mobile to mix well when 

 the ozonized air bubbles through it. When 100 cubic centims. of 

 this solution were used, and air passed through the apparatus as 

 before, the blue colour appeared at once on application of electricity, 

 and in thirty seconds it was deeply coloured. 



With dry oxygen the effects were much more rapid and remark- 

 able. 100 cubic centims. of the solution were used as before. The 

 instant the machine was put in action the liquid about the end of the 

 delivery-tube became deep blue ; and in from ten to fifteen seconds 

 the whole had acquired a uniform and intense blue colour. 



The summer moisture having interfered somewhat with the effec- 

 tive working of the electro-machine, there has been no opportunity 

 to determine the percentage of ozone produced in this manner, but 

 it appears to be very large. When dry oxygen is passed through 



( 



