聚磷酸錯塩之解離度與其水解速率之關係

The Relationship between the Dissociation Constant of Polyphosphate Complexes and its Rate of Hydrolysis

10.6623/chem.1976009

呂美芳(Mei-Fang Lu)；連鶴壽(Ho-Sou Lien)

化學

65年2期（1976 / 06 / 01）

50 - 60

繁體中文

聚磷酸根和金屬離子構成之錯鹽，若解離度小，（即形成錯鹽之能力大）則在聚磷酸鹽水溶被中加入該金屬離子時，會加速聚磷酸鹽之水解速率。金屬離子之種類和濃度一定，則聚磷酸鹽的聚合度較大者，所產生錯鹽之安定度較大，但長鏈之加水分解較快。若聚合度一定時，聚磷酸鹽的濃度大者，解離常數較小，鏈長之減短率則變大。聚磷酸鹽之一切情況相同時，金屬離子之濃度大者，形成錯鹽之能力大，聚合度之減小率則加快。與聚磷酸根會形成安定錯鹽之金屬離子之次序為：Fe^(+++)＞Cu^(++)＞Mg^(++)＞Ca^(++)＞Ba^(++)而使聚磷酸根鏈長斷製之速率為：Fe^(+++)＞Cu^(++)＞Ca^(++)≒Mg^(++)＞Ba^(++)

The rate of hydrolysis of polyphosphate chain is accelerated by the existence of metal ion which takes small dissociation constant of polyphosphate complexes. The concentration and kind of metal ion, concentration of polyphosphate, and degree of polymerization of polyphosphate are the variables of hydrolysis rate. The conditions to make small K_D (dissociation const) i. e. to form of large stability of polyphosphate complexes and to undergo rapid hydrolysis are: (1) For given metal ion with constant concentration, the larger the degree of polymerization of polyphosphates, the smaller the K_D value. (2) The concentrated polyphosphate has smaller dissociatian constant, if other factors maintain constant. (3) For larger concentration of metal ion, K_D is small. (4) More stable polyphosphate complexes are formed in the order of following metal ions: Fe^(+++)＞Cu^(++)＞Mg^(++)＞Ca^(++)＞Ba^(++) and the effect of metal ion on the rate of degradation of chain length of polyphosphate decreases in the order: Fe^(+++)＞Cu^(++)＞Ca^(++)≒Mg^(++)＞Ba^(++)