NAVAL RESEARCH LABORATORY 



No significant difference was observed between the three natural sea water samples 

 obtained from different locations when their measured velocities were compared with the 

 soimd velocities obtained by use of the empirical equation. No change in measured sound 

 velocity was detected in any of the natural sea water samples overman app.roximate_lY two- 

 week p eriod after receipt. — j 



Table 4 is a comparison of velocity values obtained from Kuwahara's tables and the 

 empirical equation. 



Figure 1 and Figures la-g are graphical representations of this equation in metric 

 units and Figure 2 and Figures 2a-p are the same graphs in British imits. Figures 3 and 

 4 show the temperature dependence of the salinity coefficient of velocity in metric and 

 British units respectively, together with a comparison of Kuwahara's values. 



Tables 5, 6, and 7 are the corrections to the velocity of sound in sea water of 35 

 parts per thousand salinity at 0°C temperature and "zero" depth (VqOq 35 ppj qp = 

 1448.6 m/sec) for changes in temperature and/or salinity. ' 



Table 5 contains values of Vj-, the temperature correction to the velocity of sound in 

 sea water of 35 ppt salinity referred to a temperature of 0° C. Table 6 contains values 

 of Vg, the salinity correction to the velocity of sound in sea water at 0" C temperature 

 referred to a salinity of 35 ppt. Table 7 contains values of Vgt, the combined salinity- 

 temperature correction to the velocity of sound in sea water of 35 ppt salinity and 0° C 

 temperature for any simultaneous changes of temperature and salinity. These tables 

 are believed to yield values of sound velocity to the same degree of precision as the 

 empirical equation, i.e., better than ±0.2 m/sec. 



THE CONCEPT OF SALINITY 



A word of caution is advisable in the physical interpretation of these tables. The 

 concept of salinity has been established by an International Commission and salinity is 

 defined as "the total amoimt of solid material in grams contained in one kilogram of sea 

 water when all the carbonate has been converted to oxide, the bromine and iodine replaced 

 by chlorine, and all organic matter completely oxidized" (8). It has been found that 

 "regardless of the absolute concentration, the relative proportions of the different 

 major constituents are virtually constant except in regions of high dilution (low salinity) 

 where minor deviations may occur" (8). * Thus salinity is usually determined by measuring 

 chlorinity, a defined term, now redefined to be made independent of changes in atomic 

 weights thus: "The number giving the chlorinity in grams per kilogram of a sea water 

 sample is identical with the number giving the mass in grams of 'atoniic weight silver' 

 just necessary to precipitate the halogens in 0.3285233 kilogram of the sea water sample." 

 Because of changes in atomic weights, the original definition of chlorinity is now called 

 the chlorine-equivalent. The chlorine-equivalent is the quantity determined by the AgNOs 

 titration, and the ratio of chloriae-equivalent to chlorinity is at present 1.00045. Neither 

 the chlorine -equivalent nor the chlorinity represent the actual amount of chlorine in a 

 sea water sample; bromine and iodine, as well as chlorine, participate in the AgNOj 

 titration, whereas fluorine does not. Neither does the salinity, by definition, represent 

 the total quantity of dissolved solids in sea water. The technique of determining the 

 defined salinity, however, yields reproducible results. The following empirical equation 

 has been obtained (8) for the dissolved solids content 



S 7oo = 0.073 + 1.8110 CI 7oo. 

 It can be shown that the total amount of dissolved solids is greater than the defined salinity. 



Not underlined in the original 



