value. The weighting function £(¢) has to satisty the 
conditions £(0) = 1 and f(~) = 0 in order to ensure a 
smooth transition to the Debye-Huckel values at lower 
concentrations. The success of any such model hinges 
essentially on the right selection of the weighting 
function, f(C). Attempts are being made to determine a 
suitable weighting function and to test the applicability 
of a similar model on sea salt solutions. 
Experimental Procedure 
Equipment: The primary element of the equipment is a 
well-stirred dewar of about four liters capacity which is 
filled with an accurately-weighed amount of one of the 
solutions to be mixed. The dewar is maintained at a fixed 
temperature by circulating constant temperature water around 
it. The temperature-ot circulating water 1s controlled gby 
a Hallikainen thermotrol, aided by a Lauda constant temper- 
ature circulation bath. For low temperature measurements, 
the Lauda circulation bath was replaced by a K4R Lauda 
refrigeration bath. Glycerol-water-mixture was used as the 
circulation Jiquid. 
The other solution to be mixed is contained in a 
Stainless steel pipet (of about 170 ce capacity) immersed 
into the dewar vessel. The low pipet capacity ensures 
that the heat of mixing is not too large to upset the near 
isothermal operation. A Rosemount platinum resistance 
thermometer is immersed into the dewar for temperature 
measurements. The thermometer is connected to a magneti- 
cally shielded and thermally insulated Leeds and Northrup 
type G-2 Mueller bridge and a Keithley model 147 nanovolt 
detector, coupled to a Leeds and Northrup speedomax 
recorder. 
A detailed description of the equipment is available 
im an earlier report (2)... A sectional view of the calorie 
meter is reproduced in Figure 12. A photograph of the 
calorimeter and related equipment is shown in Figure 13 
and a photograph of the stainless steel pipet and stirrer 
in Figure 14. 
salinity Determinations: The salinity of the Sea salt 
solutions was measured by the conductometric method using a 
Bissett Berman model 6230 salinometer. The salinity, S°7 00 
1s Telated-to the conductivity by: 
26 
