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pH测量是一种相对测量，它仅仅指示标准溶液与未知溶液之间的pH差别，实际测量时，需要用标准缓冲溶液定期进行校准。因此，为了达到量值的一致，必须建立pH标度。PH标度范围定为0～14pH，pH标度的量值由基准缓冲溶液的pHs值确定。因此，pH标度的含义可表达为：根据pH定义，在0～14pH范围内选择若干个pH缓冲溶液作为pH标度的固定点，并且采用当代技术能达到的最准确的方法测定它们的pHs值。国际上有二种pH标度，即多种基准pH标度和单种基准pH标度，中国采用多种基准pHs标度。六种基准缓冲溶液0～95℃的pHs值见下表：
六种基准缓冲溶液的pHs值
|
温度，℃
|
B1
|
B3
|
B4
|
B6
|
B9
|
B12
|
|
0
|
1.668
|
---
|
4.006
|
6.981
|
9.458
|
13.416
|
|
5
|
1.669
|
---
|
3.999
|
6.949
|
9.391
|
13.210
|
|
10
|
1.671
|
---
|
3.996
|
6.921
|
9.330
|
13.011
|
|
15
|
1.673
|
---
|
3.996
|
6.898
|
9.276
|
12.820
|
|
20
|
1.676
|
---
|
3.998
|
6.879
|
9.226
|
12.637
|
|
25
|
1.680
|
3.559
|
4.003
|
6.864
|
9.182
|
12.460
|
|
30
|
1.684
|
3.551
|
4.010
|
6.852
|
9.142
|
12.292
|
|
35
|
1.688
|
3.547
|
4.019
|
6.844
|
9.105
|
12.130
|
|
40
|
1.694
|
3.547
|
4.029
|
6.838
|
9.072
|
11.975
|
|
45
|
1.700
|
3.550
|
4.042
|
6.834
|
9.042
|
11.828
|
|
50
|
1.706
|
3.555
|
4.055
|
6.833
|
9.015
|
11.697
|
|
55
|
1.713
|
3.563
|
4.070
|
6.834
|
8.990
|
11.553
|
|
60
|
1.721
|
3.573
|
4.087
|
6.837
|
8.968
|
11.426
|
|
70
|
1.739
|
3.596
|
4.122
|
6.847
|
8.926
|
---
|
|
80
|
1.759
|
3.622
|
4.161
|
6.862
|
8.890
|
---
|
|
90
|
1.782
|
3.648
|
4.203
|
6.881
|
8.856
|
---
|
|
95
|
1.795
|
3.660
|
4.224
|
6.891
|
8.839
|
---
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