The nature of the ions produced by the spraying of water

Abstract

In a paper on the electrification of water by splashing and spraying the author gave a brief account of the nature of the ionisation which accompanies these processes. In a later paper these results were extended. It was shown that when pure water is sprayed, ions of both signs are produced, negative being in excess. These ions are found in a certain number of distinct groups, each group having a characteristic mobility. There is no variation of mobility with time, that is to say, ions of any specified mobility will be found if an examination is made over as wide a range of time as is experimentally possible between the production and disappearance of the ionisation. The mobilities found were:- 0·00038, 0·0010, 0·0043, 0·013, 0·046, 0·12, 0·24, 0·53, 1·09, 1·56, 3·27 and 6·5, all being expressed as the velocity of the ion in centimetres per second in a field of 1 volt per centimetres. As far as mobilities are concerned, no difference between the positive and the negative ions was found except that the fastest ion (mobility 6·5) was not found with a positive charge. In an investigation of the ionisation produced by bubbling air through mercury, Prof. McClelland and P. J. Nolan found five distinct groups of ions, the mobilities of the ions in this case depending on the time elapsing from their production and also on the degree of dryness of the air. When the air was dried, or when the ions were examined as soon after formation as possible, comparatively high values of mobility were obtained. With damp air the mobilities were lower, and by increasing the time-interval between production and observation the ions could be brought to a final steady mobility. The mobilities of the five groups in this state agreed very well with the mobilities of the five slowest ions produced from water. In a joint discussion it was suggested that these five ions are the same in each case, but that when produced by the breaking up of mercury, they take some little time to add on enough water to attain to their final steady state. We imagined them therefore as water aggregates of five different sizes. In the present paper a more definite theory will be submitted as to the constitution of these ions, a theory which in the light of the fuller account which can now be given of the more mobile ions can be made to cover all the ions observed.