Pressure,
decibars
0
2,685
5,064
7,675
10,487
Table 3.
The relative refractiv
Temperature, 0°C
Waveleneth, nanometars
Density
467.82
1.33912
1.34335
1.34695
1.35067
1.35440
501.57
1.33734
1.34158
1.34513
1.34884
1.35257
527 + 56
1.33400
1.33819
1.34174
1.34541
1.34908
g/ml (old)
0.99987
1.01297
1.02385
1.03535
1.04679
1b/ft
62.418
63.236
63.915
64.633
65.347
Relative Refractive Index of Pure Water
index expressed in Table 3 is effective
for a temperature of 0°C rather than the test temperature of
1.56°C for the purpose of convenience. Pressure is listed in
decibars since the unit of pressure in decibars is frequently
encountered in oceanographic literature. It is also of interest
to indicate that the sea water depth in meters is approximately
equal to the sea water pressure in decibars. The reciprocal of
the specific gravity in milliliters per gram is equal to the
density in grams per milliliter. In Tables 2 and 3, (old) was
inserted subsequent to ml/g and g/ml to indicate the old liter
prior to redefining the liter in October 1964(Ref. 4). The
difference in the volume of the liter is only 28 parts per
million. The majority of available tables list density in
g/ml(old) since the volume difference is only significant in
measurements of high accuracy. Table 3 also includes density
in pounds per cubic foot. The density of water in these units
is frequently presented in tables. To convert g/ml(old) to
pounds per cubic foot, multiply by 62.h262.
The Gladstone-Dale equation is used to determine the water re-
fractive index that is effective for a given water density when
a different water density and its corresponding water refrac-
tive index are known. The equation is based on the condition
that the temperature and the salinity, if sea water, remain
constant while the density varies owing to a change in water
pressure. The Gladstone-Dale equation is developed as follows:
n -1
0
Eq. 10
P. q
where
known refractive index of water for density of Po
known density of water in g/ml(old)
constant.
