known for a long time, but the Soviets seem to have achieved a degree 

 of success never before attained. Some observers expressed the belief 

 that the Soviet claim is authentic. 



5. Beta particle absorption instrument 



The measurement of density by beta particle absorption has 

 been suggested by Dr. Donald Hood of Texas A&M as a method of 

 obtaining sea water densities. 



Accuracies of ±0.0002 gram per milliliter may be obtained for 

 binary liquid mixtures. For complex liquid mixtures, such as sea 

 water, the accuracy would depend upon the degree to which the overall 

 composition of sea water varies. 



A laboratory instrument is currently available from Hallikainen 

 Instruments of Berkeley, California. The assembly consists of two 

 radioactive sources, two liquid cells, and two ionization chambers 

 mounted in a temperature controlled block. In normal operation one 

 cell is filled with a reference liquid and the other with either a static 

 or flowing sample of the liquid to be analyzed. Beta particles from 

 each source pass into its corresponding cell where some are absorbed. 

 The transmitted particles pass into the ionization chamber and produce 

 ions which result in the flow of an electrical current. The difference 

 between the two ion currents is amplified and recorded and is related 

 to density differences. Strontium 90 is used as a radiation source and, 

 when assembled in the apparatus, produces a radiation level that is 

 about one-half of the currently accepted safe level for 40 hours per 

 week of exposure. 



One major problem that is immediately apparent, but as yet 

 unexplained, is the effect that dissolved gases and organic matter 

 will have on the determinations. These substances, which may sub- 

 stantially alter the in situ density value, may have to be driven off 

 or completely oxidized before analysis. 



D. SUMMARY AND CONCLUSIONS 



For in situ measurements, the equipment described by Hamon and 

 Brown, with its accuracy of ±0.05%o of salinity, seems to have attained 

 the greatest degree of success of any of the electrode-type conductivity 

 instruments. However, in order to obtain in situ salinity to a desired 

 accuracy of ±0.02%o the instrument employed must be capable of meas- 

 uring temperature to ±0.02°C and conductivity to ±0.02 millimho. 



IV- 10 



