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 |
--- |
|
