Being based on the following principle, the apparatus was constructed : The ice crystals produced from supercooled fog will, every time they strike against an electrically heated metal (platinum) wire and come to be held thereon, cool the wire half a moment as they each absorb from it the heat of volatilization, leading to the decreases in electrical resistance of wire and, therefore, to the increases in electrical current flowing through it ;these are tape-recorded as pulses in voltage, which are transmitted successively to a discriminative system composed of electronic circuit in order to separate themselves from disturbing noises and are, then, detected by means of oscillography and/or the electronic counter method, the freezing temperature being determined as the temperature from which onwards the count of pulses rises sharply. As for the discriminative system described above, two types (A and B) were examined in turn, and the latter was found to be more available.The apparatus was tested with fogs of aqueous solution of KCl (10-5N) and of K3PO4 (10-5N), their average droplet size being both s p in diameter. Comparison was made, for the fogs obtained from KCl solutions (10-1-10-6N), between the Bigg's sugar solution method and those in the present and previous reports, with the finding that there exists a good correspondence.Further experiments have been done, using the apparatus, with a variety of electrolyte containing fogs. The results obtained and its discussion will be given in the next communication.
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