156 MAYOR— DETECTING OCEAN CURRENTS. 



Locality. PH of Sea Wa-er. 



Black Sea l^"'-^"^^ ^"^l 



^deep water 745 



Sea of Marmora and Bosphorus 8.35 



Eastern Mediterranean 8.27 



Western Mediterranean 8.22 



Coast of Portugal 8.25 



Off Scotland and Faroe Is 8.08-8.22 



S.E. part of North Sea and Skagerak 8. -8.05 



Methods. 



The hydrogen-ion concentration of sea water was tested by the 

 simple process of placing 0.4 c.c. of Yio of i per cent, thymolsulpho- 

 nephthalein in a non-soluble glass test tube of 24 mm. caliber and 

 adding 30 c.c. of the sea water to be tested. Highly alkaline sea 

 water gives a blue-green solution, while relatively acid water gives 

 a greenish-yellow color. Then by comparing this test tube with a 

 series of sealed tubes of similar caliber containing mixtures of 

 borax, boracic acid and sodium chloride of various known hydrogen- 

 ion concentrations we can at once determine the concentration of 

 our sample sea water with an error of not more than 0.025 PH. 



McClendon, Gault and Mulholland, 1917, were the first to stand- 

 ardize sodiurii borate and boracic acid mixtures for use in measuring 

 the hydrogen-ion concentration of sea water with thymolsulpho- 

 nephthalein as an indicator. Their solution consists of 0.075 """• 

 sodium borate (28.67 grams of Na.B^Oj-ioH.^O), and 19 grams of 

 sodium chloride, dissolved in water so as to make up 1,000 c.c. of 

 solution. The other solution consists of 0.3 m. boric acid (18.6 

 grams of H3BO3) and 22.5 grams of sodium chloride dissolved in 

 water so as to make up a liter of solution. Definite mixtvires of 

 these two solutions give correspondingly definite hydrogen-ion con- 

 centration, as is shown by McClendon, Gault and Mulholland, p. 44, 

 1917. 



Professor McClendon kindly gave me a set of these tubes which 

 I have used on voyages to test the hydrogen-ion concentration of 

 the surface water of the ocean. The readings of these tubes were 

 compared with those of a Leeds and Northrup potentiometer stand- 

 ardized by the U. S. Bureau of Standards. IMcClendon thus tested 

 their accuracy in 1917 and I repeated the process in April, 1919, 



