1134 
attraction increases as the size of the ion decreases. 
Water molecules thus attracted form the so-called water 
coating. Owing to the particular spatial conditions 
which cause a stronger pull of the large ions toward the 
interior, the hydrated ions now become arranged toward 
the center in the order of increasing size of their coat- 
ing, whereas the “bare” ions (in this case the Cl) 
accumulate on the surface. Jebsen-Marwedel [80] states 
that for similar phenomena in fluid glass the ‘‘bare”’ 
ions, that is, those with smaller molecular forces, are 
squeezed into the surface. According to Benson [2], 
this surface activity as a preliminary stage of molecu- 
lar separation is a familiar phenomenon in the case of 
foam. However, according to Whitney and Grahame 
[58], it also represents the basic reason for the occurrence 
of the electrical double-layer. Undoubtedly, this surface 
activity is also the basis for the electrical double-layer 
of droplets suspended in the atmosphere. 
Ballo-Electricity. The precipitation electricity (Len- 
ard effect, that is, negative charge of the fine particles 
and positive charge of the somewhat coarser ones) must 
also be affected by the order of hydration, according 
to the discussion above, because of its dependence on 
the double-layer. To prove this, experiments with 
atomization of drops in thunderstorm updrafts and 
experiments with falling drops (rain) were undertaken 
using dilute aqueous solutions of MgCl, and 
[Mq(NH3)6|Clo, corresponding to the concentration in 
raindrops. The atomized droplets were chemically ana- 
lyzed and tested for charge at various distances up to 
3 m from the nozzle. These tests were made in the same 
way with the falling of the central drops and the small 
secondary drops [12]. The investigations yielded the 
following information: . 
In addition to the appearance of the Lenard effect, 
a chemical separation occurred in the atomized drops 
such that the fine particles, which drifted to some dis- 
tance after being torn from the bulk surface, were en- 
riched with CI- ions and showed a decreased pH value 
(more acid), whereas the coarser particles which settled 
more rapidly were enriched with cations and showed a 
higher pH value. In the case of the falling drops the 
same difference could be found between the coarse main 
drop and the fine secondary drop which represents the 
outermost shell of the total drop. 
Therefore, the separation of pairs of ions is to be re- 
garded as an almost confirmed cause for the ballo- 
electric charge in the case of the Lenard effect. 
According to the concepts of Simpson [52] and the 
presentation of Israél [29], the repeated breakup of the 
water drops in the cloud by updrafts is, indeed, the fuel 
of the storm machine. However, the then unknown 
electrical agent which is effective during this drop 
disintegration and which is responsible for a continu- 
ously renewed occurrence of the Lenard effect, can now 
be considered as recognized in the order of hydration 
that repeats itself after each drop breakup. The mecha- 
nism of the processes has not yet been explained in all 
its details, nor is the significance of this effect for 
thunderstorm formation completely understood. 
Electrical Charge by Adhesion. In continuation of the 
BIOLOGICAL AND CHEMICAL METEOROLOGY © 
concepts outlined above, this process is also linked to 
the order of hydration. This process takes place on sus- 
pended droplets and hence is not associated with drop 
disintegration, but is produced by the adhesion of a 
gas molecule, ionized by cosmic radiation, secondary 
radiation, etc., or by adhesion of a small ion. The ad- 
hesion to droplets is in all probability a selective process. 
If positive chemical ions are accumulated in the bound- 
ary layer of the droplet, negative particles are at- 
tracted and positive ones are repelled. If some other 
type of chemical phenomenon is responsible for the 
accumulation of negative ions in the boundary layer, 
the reverse occurs. This concept of the control of the 
charging process by chemical phenomena leads also 
to the explanation of the unipolarity of clouds. Accord- 
ing to this working hypothesis, droplets of like origin 
and hence of like chemical composition must assume 
charges of the same sign. A selective association of small 
charge carriers was observed by Tyndall [55]. Accord- 
ing to him, alcoholic gases capture principally negative 
carriers and this effect increases with an increase in the 
length of the carbon chain. If the dipole group OF is 
removed from such compounds, any effect on carriers 
ceases. Thus, one can imagine that clouds whose ele- 
ments are of uniform chemical composition act like a 
filter on the smallest charge carriers of one sign. If, 
for example, over extended areas of blossoms (Prunus), 
heated air cools adiabatically as it rises to a greater 
altitude and forms droplets with an excess of the NHf 
cation in the surface layer, these droplets must become 
negatively charged. Conversely, droplets suspended di- 
rectly above (as in inversions) with an excess of NOz 
in the surface layer (condensation on nitrites) would 
become positively charged. Observations pointing in 
this direction (specifically, data from chemical experi- 
ments) were obtained in the High Tatra (Szepes, Slo- 
vakia) during the development of areal thunderstorms 
[11, 12]. Perhaps such a phenomenon is the explanation 
for the fact that frequently the upper portions of the 
thunderheads were positively charged while the bottom 
portions were negatively charged. During the penetra- 
tion of droplets into clouds having a different type of ~ 
chemical make-up, or opposite charge, electrical bal- 
ancing processes and coagulation result. The conse- 
quence of this, in turn, is a different chemical make-up 
of the new droplets and thus new, rapid, layerwise 
coagulation. It is possible that the rapid fluctuations of 
the electrostatic field are correlated with such filter and 
coagulation processes. If this is true, perhaps these 
processes also control the stronger or weaker produc- 
tion of O3 at the tips of grounded conductors as well as 
in nonhomogeneous fields between clouds. Their pos- 
sible significance for thunderstorm formation cannot 
yet be evaluated from the available experimental data. 
Ice-Particle Charging. This process was recognized 
as one of the most important sources of thunderstorm 
electricity in the informative studies by Findeisen [26] 
and might, in the final analysis, have no other origin 
than a chemical separation. Although in the case of ice 
a hydration equal to that in droplets cannot exist, at 
least a boundary layer arrangement with a double- 
