10 



U. S. COAST AND GEODETIC SURVEY 



change occurs. The observer should subtract 0.05 c. c. from the 

 burette reading for each of these drops (inckiding the one left hang- 

 ing from the tip of the burette). 



5. Replace the rubber stopper snugly in the top of the burette. 

 Rinse the beaker, evaporating dish, stirring rod, and 10-c. c. pipette 

 with fresh water or distilled water (from the wash bottle), and the 

 1-c. c. pipette with distilled loater. 



The apparatus will then be ready for the titration of the next 

 sample. 



Experiments were conducted on board the Lydonia to determine 

 how consistent would be the values obtained for the salinity of a 

 given sample by the above method by several officers that were 

 wholly inexperienced in titrations. Each one made his determina- 

 tion independently, without knowing the results obtained by the 

 others. The ship was rolling 10° to 15°. The re^ults are shown in 

 Table 3. It is reasonable to expect that the results would be more 

 concordant after each of the officers had made a few titrations. 



Table 3. — Independent observations of the salinity of a given sample of sea 

 water by the chemical titration method 



Note.— The first three observers had had no previous experience with this method. 



Professor Giral ^ states that variation in the proportion of chlorine 

 in the total dissolved solids in different regions is such that no more 

 than three significant figures are justified in salinity values computed 

 from the results of chlorine titrations. From data obtained from 

 Clarke's The Data of Geochemistry it has been estimated that the 

 variation from 55.25 per cent chlorine in total dissolved solids may 

 cause an extreme error of three or four units in the third significant 

 figure but not more than one unit in the third significant figure in 

 the waters along the Atlantic and Pacific coasts of the United States. 



While the method described above will doubtless meet all the needs 

 of the echo-sounding work of the United States Coast and Geodetic 

 Survey, attention is called to the more precise, although somewhat 

 more difficult, technique involving the use of the salinity outfit sup- 

 plied by the Copenhagen Laboratory of the Conseil permanent inter- 



1 Conseil permanent International pour I'Exploration de la Mer. Publication de Cir- 

 constance No. 90. 



