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Diatomaceous earth, which is found throughout the world, is mainly composed of diatom crusts associated with a small amount of clay and detrital rocks. The diatom crust, amorphous silica, is characterized by dissolution in caustic alkaline solution. In this study we examined the distribution of silica and trace elements leached from diatomaceous earth by 10 w / v % NaOH solution in detail. The results are as follows:(1) 31 diatomite samples of seawater origin were collected from 4 ore deposits located in Akita Prefecture and 28 samples of freshwater origin were collected from 2 ore deposits in Okayama and Oita Prefecture. The specimens mainly consisted of a white or grayish white assemblage of diatoms in the range of m ~ mm order.(2) By qualitative analysis, abundant silica and small amounts of 16 elements in dissolved solutions were detected, while the presence of 26 elements in bulk specimens were confirmed.Taking into account the sensitivities of the AAS and ICP-AES analyses, Si, Al, K, Fe and B were quantitatively analyzed. An abundance of silica extracted from diatomite reached 86 ~ 98 % in bulk samples, Al, K and Fe content were relatively high in the range of 25,000 ~ 200 ppm. B was present at the less than 150 ppm. Based on similarities among the distribution patterns of each element, it was observed that Silica and B were derived from diatoms, and Al, K and Fe from detrital rocks.(3) The need for high quality silica as a raw material has been increasing, and reserves of high purity quartz will be exhausted in the near future; thus, how to produce high quality silica from diatomaceous earth is of great importance. In particular, the B content in silica must be very low below a few ppm. At present, some solutions extracted from diatomite with a freshwater origin have lower concentrations (4.3 ~ 13 ppm) than those of seawater origin(80 ~ 150 ppm). From the data we suggest that diatomaceous earth should be considered as a potential source of high purity silica.

The electric field influence of 1 volt on the typical polymer electrolyte fuel cell catalyst system carrying Pt clusters on amorphous carbon particles have been elucidated by transmission electron microscope observation. The same position was observed before and after exposing to the electric field. Surface of Pt clusters were covered with a few graphitic layers. The slight graphitization of amorphous carbon particles has been also occurred. The growth of Pt clusters has been discussed as the aggregation of the Pt atoms which exist on carbon particles.

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