Nolan and Enright — Electrification Produced by Breaking up Water. 3 



water could be broken into drops of a regular and controllable size by forcing a 

 jet through a narrow orifice. A jet of this sort will break up into drops of 

 equal sizes in accordance with any frequency impressed on it. When the 

 electrical test was made, however, it was found that the degree of charging 

 produced was very minute in comparison with that in water broken up by a sprayer 

 or by an air-blast. This result should perhaps have been anticipated, for it is well 

 known that the electrical separation at the water- air surface takes place only when 

 there is rupture of the water-surface with some degree of violence. In the 

 formation of drops from the unstable water-jet, the only rupture that occurs is 

 the final break at each end of the minute cylindrical neck that forms between two 

 adjacent drops. 



We reverted, therefore, to the sprayer as a means of breaking up the water. 

 The sprayer, which was of metal, was fitted to a bottle containing the water to be 

 sprayed. The sprayer was driven by air contained in a large vessel under pressure. 

 The spray was projected horizontally, and was received on a shallow zinc vessel 

 120 ems. long and 60 cms. broad, which was placed horizontally 40 cms. below the 

 level of the sprayer. This receiving vessel was insulated by paraffin supports. 

 The spraying bottle was also insulated, an insulating section being inserted into 

 the tubing connecting it with the high-pressure air-supply. The apparatus was 

 surrounded by a screen of wire netting connected to earth. 



In investigating the charge on the water, it is necessary to eliminate effects due 

 to actions between the water and the nozzle of the sprayer. Thus there might be 

 a " water-dropper " effect, though this is unlikely to cause any appreciable charg- 

 ing owing to the good screening. Frictional effects between the issuing water and 

 the nozzle must also be considered. If the spraying bottle and the receiving 

 vessel are connected together, all effects of this kind are automatically eliminated, 

 provided that all the water is captured. The charging of the combined system will 

 then be due to the genuine air-water effect, the opposite charge being carried away 

 in the air as an excess of negative ions. This was the method of working employed 

 in practically all cases. Care was taken to ensure that all the spray reached the 

 receiving vessel, and both vessel and sprayer were connected to the Dolezalek 

 electrometer, with which the charge was measured. 



Various methods of estimating the size of the drops were tried. Some of these 

 were on lines already indicated. Test plates were introduced, and the drops 

 falling on a certain area in a known time were counted. A second experiment 

 gave the weight of water falling on the same area in a known time under the same 

 conditions. Thus the average volume of the drops was deduced. But, as has been 

 pointed out, this may give very illusory results when there is much variation in 

 the size of the drops. In addition, evaporation is a serious trouble in both parts 

 of the experiment. The method finally adopted is convenient and accurate, and 

 may be recommended for measurements of this character. Glass microscope slides 

 were prepared by spreading out on each a layer of thick dark oil (density 0-9). 

 Wlien one of these slides was exposed to the spray, the small drops falling on it 

 passed into the oil-layer and were there suspended, sinking very slowly. The rate 

 of movement through the oil was so slow that the smallest drops did not reach 

 the bottom of the layer until after forty-eight hours. While suspended in the oil 

 the diameters of the drops could be easily measured with a low-power microscope. 

 We were thus enabled, by taking a sufficient number of observations, to determine 

 the sizes of the drops to any degree of accuracy required. 



The total amount of water per second passing through the sprayer for any 

 given air-pressure was easily measured by capturing all the water coming from 



b2 



