冨士川,狩野川の珪酸,燐酸その他の化學的調査及び一般天然濁水の燐酸定量に關する問題に就て

附三島附近天然水の化學的調査

抄録

We measured water temperature, hydrogen ion concentration, SiO₂, P₂O₅, and Cl Contents of the water of the rivers Huzigawa and Kanogawa over the period from Sep. 1935 to Sep. 1936. As the water of the Huzigawa was found to be turbid for the most part of the year, Denigeés' method for P₂O₅, as it is, could not yield but very rough value, whose average came out to be 0.060mg/L. We tried a new method to make the turbid water transparent, adding a drop of 50% H₂SO₄ and 10mg of alum for 100cc of the test water and filtering after a day or two. Then we applied Denigeés' method and obtained 0.218mg/L as the average value. The discrepancy of the above two values, which is too serious to be attributed to the difficulty in colorimetry for turbid test water, may in all probability be due to the dissolution of P₂O₅ contained in the suspension during the process of making transparent. We now come by a question as to the meaning of P₂O₅ content of turbid water whose suspension contains itself P₂O₅. Apart from this question, it is a matter of interest that Mr. K. Kimura, measuring P₂O₅, SiO₂, etc. on board a ship at several points in north Suruga Bay in 1931, found that P₂O₅ content of the surface sea-water at the point 1400m SW from the mouth of the river Huzigawa amounts to 0.250mg/L-the value markedly large in comparison with those at other points, while Mr. E. Kurasige in 1933 reported 0.0321mg/L as the average value of P₂O₅ content of the water of the Huzigawa-the value not reconcilable with the former. In the light of our present investigation, it may be possible that P₂O₅ contained in the suspension in the river water dissolves under suitable condition in the sea, and if this is the case, the above mentioned relation can be explained at once. It is also a matter of interest that, “Sakura-ebi” (Sergestes prehensilis) which had been found only near the mouth of the Huzigawa was found last year in the offing of Okitu and Miho where P₂O₅ content is large next to the mouth of the Huzigawa according to Mr. K. Kimura. It seems that abundance in P₂O₅ has some connection with the yield of Sakura-ebi, but it is not exactly known.
Jan. 15, 1937, At Misima.