n refractive index of water to be 
determined for a given density of p 
p = given density of water in g/mi(old) 
K constant per Eq. 10. 
The water refractive indexes determined by the Gladstone-Dale 
Eq. 12 for the different densities vary slightly when compared 
with the water refractive indexes presented in Table 3. Eq. 12 
is modified as follows by using the water refractive indexes 
listed in Table 3 as the basis for the modification: 
2 
n = l4Kp-(p-p,)1.25x10. Eq. 13 
Table 4 is a tabulation of the water refractive indexes de- 
termined by Eq. 13 to compare with the experimentally deter- 
mined values listed in Table 3. 
Temperature, oc 
Pressure, 
decibars 
0 
2,685 
5,064 
7,675 
10,487 
Wavelength, nanometers 
467.82 
1433013 
1.34339 
1.34695 
1.35071 
1.35444 
501.57 
1.33734 
1.34159 
1.34513 
1.34886 
1.35258 
587 + 56 
1.33400 
1.33821 
1.34171 
1.34908 
Relative Refractive Index of 
Pure Water by Eq. 13 
Table 4, 
The maximum deviations of the water refractive indexes listed 
in Table 4 from the laboratory determined values listed in 
Table 3 are «0.00004 and -0,00003, 
It is of interest to point out that the computation of the 
water refractive indexes owing to changes in water densities 
caused by changes in water pressures were more accurately de- 
termined by the Gladstone-Dale equation than the Lorentz- 
Lorenz equation. However, it was necessary to modify the 
Gladstone-Dale equation to obtain the relatively insignificant 
maximum deviations of +0.00004 and -0.00003 referred to in the 
previous paragraph. 
In the preparation of Table 4, the constant K was determined 
for each of the three wavelengths with the values of the water 
refractive index and the water density taken from Table 3 at 
the water pressure of zero decibars. The constant K can be 
determined for any water pressure as is demonstrated in the 
numerical example that follows: