Abstract
Nickel oxide has, next to silver iodide, an excellent ice-nucleating ability (nucleation temperature, -7°C). With the intention of testing its practical applicability to rain-making, we have performed a field experiment from January 27 to February 4, 1956 on the outskirts of Takayama City, Gifu Prefecture.
Nickel oxide was prepared through thermal decomposition of the carbonate, and the powder obtained was sent up, after thorough pulverization, into the sky by a dust-ejector. We have succeeded in deriving snow from the atmosphere at temperatures as low as -12° to -16°C, but never experienced, as expected, any appreciable snow-fall when the air temperature was higher than -7°C.
In order to seek after the diffusion of the nickel oxide smoke in the atmosphere, we have, keeping pace with the progress of experiment, made a trial of detecting nickel oxide in the air around the seeding-station by a dimethyl glyoxime indicator method.
The ice crystals whose formation is considered to be due to the seeding were fixed to replicas; they were classified according to their shape to plate-like, columnar, stellar, dendritic and so on; particularly, the size of the plate crystals was measured and it was found to range from 30 to 210μ in diameter.
