ecomposition of Condensed Sodium Phosphate in Heating Brine Obtained by the Ion Exchange Membrane Method

In the concentration of brine by the use of the ion exchange membrane the relationship between the formation of alkaline scale and the decomposition of the condensed sodium phosphate, a scale inhibiter, was- tested. This phenomenon was studied by the laboratory and practical tests, described in the previous paper. In this case the phosphate ion, the decomposition product of the condensed sodium phosphate, was analyzed quantitatively by the solvent chloroform+buthanol extraction method. The results are as follows: 1) The effects of sodium hexameta-phosphate on the inhibiter of alkaline scales in the brine with the concentration-factor 1.8, is sufficiently large at 50°C, but is extremely small at 75° and 100°C. 2) Under the boiling and concentrating conditions the close relation between the decomposition of sodium hexameta-phosphate and that of carbonates is found; the former increases with an increase of the latter. 3) At 100° and 50°C, the rates of decomposition of sodium hexameta-phosphate in the decarbonated brine decrease to 1/50 and 1/20 of those of the non treated brine, respectively. 4) In concentrating the brine to the concentration-factor 1.8 at boiling temperature 100°C, 97.8, 0.98 and 1.25% of the added sodium hexameta-phosphate are transferred, to the deposited scale, the common salt, and the mother liquid, respectively. 5) Sodium penta-calcium sulfate (Na2S0, 5 CaSO4 H20) is found in the scales deposited on the inner place of the pans which are practically operated at the concentration-factor of about 15 and at 66° and 88°C.