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preface to fifteenth edition

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2.98 SECTION 2<br />

TABLE 2.21 Transmittance-Absorbance Conversion Table<br />

From Meites, Handbook of Analytical Chemistry, 1963, McGraw-Hill Book Company; by permission.<br />

This table gives absorbance values <strong>to</strong> four significant figures corresponding <strong>to</strong> % transmittance values which<br />

are given <strong>to</strong> three significant figures. The values of % transmittance are given in the left-hand column and in the<br />

<strong>to</strong>p row. For example, 8.4% transmittance corresponds <strong>to</strong> an absorbance of 1.076.<br />

Interpolation is facilitated and accuracy is maximized if the % transmittance is between 1 and 10, by multiplying<br />

its value by 10, finding the absorbance corresponding <strong>to</strong> the result, and adding 1. For example, <strong>to</strong> find<br />

the absorbance corresponding <strong>to</strong> 8.45% transmittance, note that 84.5% transmittance corresponds <strong>to</strong> an absorbance<br />

of 0.0731, so that 8.45% transmittance corresponds <strong>to</strong> an absorbance of 1.0731. For % transmittance values<br />

between 0.1 and 1, multiply by 100, find the absorbance corresponding <strong>to</strong> the result, and add 2.<br />

Conversely, <strong>to</strong> find the % transmittance corresponding <strong>to</strong> an absorbance between 1 and 2, subtract 1 from<br />

the absorbance, find the % transmittance corresponding <strong>to</strong> the result, and divide by 10. For example, an absorbance<br />

of 1.219 can best be converted <strong>to</strong> % transmittance by noting that an absorbance of 0.219 would correspond<br />

<strong>to</strong> 60.4% transmittance; dividing this by 10 gives the desired value, 6.04% transmittance. For absorbance values<br />

between 2 and 3, subtract 2 from the absorbance, find the % transmittance corresponding <strong>to</strong> the result, and divide<br />

by 100.<br />

%<br />

Transmittance<br />

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9<br />

0 ...... 3.000 2.699 2.523 2.398 2.301 2.222 2.155 2.097 2.046<br />

1 2.000 1.959 1.921 1.886 1.854 1.824 1.796 1.770 1.745 1.721<br />

2 1.699 1.678 1.658 1.638 1.620 1.602 1.585 1.569 1.553 1.538<br />

3 1.523 1.509 1.495 1.481 1.469 1.456 1.444 1.432 1.420 1.409<br />

4 1.398 1.387 1.377 1.367 1.357 1.347 1.337 1.328 1.319 1.310<br />

5 1.301 1.292 1.284 1.276 1.268 1.260 1.252 1.244 1.237 1.229<br />

6 1.222 1.215 1.208 1.201 1.194 1.187 1.180 1.174 1.167 1.161<br />

7 1.155 1.149 1.143 1.137 1.131 1.125 1.119 1.114 1.108 1.102<br />

8 1.097 1.092 1.086 1.081 1.076 1.071 1.066 1.060 1.056 1.051<br />

9 1.046 1.041 1.036 1.032 1.027 1.022 1.018 1.013 1.009 1.004<br />

10 1.000 0.9957 0.9914 0.9872 0.9830 0.9788 0.9747 0.9706 0.9666 0.9626<br />

11 0.9586 0.9547 0.9508 0.9469 0.9431 0.9393 0.9355 0.9318 0.9281 0.9245<br />

12 0.9208 0.9172 0.9136 0.9101 0.9066 0.9031 0.8996 0.8962 0.8928 0.8894<br />

13 0.8861 0.8827 0.8794 0.8761 0.8729 0.8697 0.8665 0.8633 0.8601 0.8570<br />

14 0.8539 0.8508 0.8477 0.8447 0.8416 0.8386 0.8356 0.8327 0.8297 0.8268<br />

15 0.8239 0.8210 0.8182 0.8153 0.8125 0.8097 0.8069 0.8041 0.8013 0.7986<br />

16 0.7959 0.7932 0.7905 0.7878 0.7852 0.7825 0.7799 0.7773 0.7747 0.7721<br />

17 0.7696 0.7670 0.7645 0.7620 0.7595 0.7570 0.7545 0.7520 0.7496 0.7471<br />

18 0.7447 0.7423 0.7399 0.7375 0.7352 0.7328 0.7305 0.7282 0.7258 0.7235<br />

19 0.7212 0.7190 0.7167 0.7144 0.7122 0.7100 0.7077 0.7055 0.7033 0.7011<br />

20 0.6990 0.6968 0.6946 0.6925 0.6904 0.6882 0.6861 0.6840 0.6819 0.6799<br />

21 0.6778 0.6757 0.6737 0.6716 0.6696 0.6676 0.6655 0.6635 0.6615 0.6596<br />

22 0.6576 0.6556 0.6536 0.6517 0.6498 0.6478 0.6459 0.6440 0.6421 0.6402<br />

23 0.6383 0.6364 0.6345 0.6326 0.6308 0.6289 0.6271 0.6253 0.6234 0.6216<br />

24 0.6198 0.6180 0.6162 0.6144 0.6126 0.6108 0.6091 0.6073 0.6055 0.6038<br />

25 0.6021 0.6003 0.5986 0.5969 0.5952 0.5935 0.5918 0.5901 0.5884 0.5867<br />

26 0.5850 0.5834 0.5817 0.5800 0.5784 0.5766 0.5751 0.5735 0.5719 0.5702<br />

27 0.5686 0.5670 0.5654 0.5638 0.5622 0.5607 0.5591 0.5575 0.5560 0.5544<br />

28 0.5528 0.5513 0.5498 0.5482 0.5467 0.5452 0.5436 0.5421 0.5406 0.5391<br />

29 0.5376 0.5361 0.5346 0.5331 0.5317 0.5302 0.5287 0.5272 0.5258 0.5243<br />

30 0.5229 0.5214 0.5200 0.5186 0.5171 0.5157 0.5143 0.5129 0.5114 0.5100

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