Substituting the indexes of refraction in Eq. 3, three siuml- 
taneous equations with three unknown constants are as follows: 
1.3402352 = a+450"“b+450""e 
ae ns 
1.3374146 2 b«5007^b4500^ c 
} 
O9. ín" 
1.3352917 = c+550 b+550 Ce 
Solving the three equations simul taneously, the constants are 
Substituting the three constants in Eq. 3, the derived equation 
for the refractive index of distilled water at 0 C is as 
follows: 
4 
^ a] 3 A 2 , e 4j " = 
n = 1.32476+3.29x10-A 32x10 4 + Eq. 5 
Eq. 5 accommodates a change in wavelength but is confined to 
a constant temperature of 0°C, The change in the refractive 
index of distilled water owing to a change in the temperature 
from O C is 
-6m2 
Am = YX J À e Eq. 6 
Adding Eq. 6 to Eq. 5 results in the following equation for 
the refractive index of distilled water that accommodates a 
change in wavelength and temperature: 
n = 1432807645,293107172 3,231047 5-2, 5:107 67, Eq. 7 
Ref. 2 is the classical technical publication on the refractive 
index of distilled water at atmospherig pressure for visible 
radiation at temperatures from 0 to 60°C. Table 7 of Ref. 2 
lists the refractive index of distilled water to seven decimal 
places. Table 1 lists in Column (1) the refractive indexes of 
distilled water to five decimal places from Table 7 of Ref. 2 
for wavelengths from 425 to 600nm in increments of 25nm and for 
temperatures of 0, 10, and 20%. Column (1) lists the precise 
values of the refractive index of distilled water that are used 
to determine the errors of empirical solutions. Column (2) 
lists the refractive indexes of distilled water that are com- 
puted from Eq. 2. Similarly, Column (3) is computed from Eq. 7. 
The errors of Eq. 2 and Eq. 7 are listed in the last two columns. 
The maximum errors of Eq. 2 range from -0,00171 to +0.00034, 
If the first term of Eg. 2 is changed from 1.338 to 1.3387, 
the maximum errors of Eq. 2 range from -0.00101 to +0.,00104, 
The maximum errors of Eq. 7 range from -0.00004 to +0.00004 
which are insignificant from a practical operational viewpoint. 
The change in the refractive index of distilled water to sea 
water, owing to the presence of various salts, is 
- 5 
J 
SJ. Eq. 8 
=2 
Ang = (5-2x10 T)(3.98x10