44 



INJURY, EECOVERY, AND DEATH 



value is about 10. This is evident from Fig. 16, which 

 shows the increase of pH value as alkali is added to sea 

 water.^" It is therefore evident that small amounts of 

 alkali affect the resistance. 



-13 



Fig. 16. — Curve showing changes in the hydrogen ion concentration of sea water upon the 

 addition of alkali at 21° C. Ordinates show the hydrogen ion concentration. In passing 

 from 1X10-^ to 1X10-*' the successive divisions are read as follows: 9, 8, 7, 6, 5, 4, 3, 2, 1, 5, 1, 

 each multiplied by 10-*. Abscissae show burette readings beginning at 7.28 cc. and ending 

 at 9 cc. The curve shows that on adding alkali to sea water the hydrogen ion concentration 

 at first falls rapidly and then very slowly until the magnesium hydrate has all been precipi- 

 tated. After this further additions of alkali cause a more rapid fall in the concentration of the 

 hydrogen ion, but this is soon checked by the precipitation of the calcium hydrbiide. After 

 the calcium hydroxide is all precipitated further additions of alkali will cause a corresponding 

 decrease in the concentration of the hydrogen ion. 



The efficiency of OH in decreasing resistance is strik- 

 ingly shown in Fig. 17, which illustrates the rapid fall 

 of resistance in NaCl + Ca(0H)2 as compared with 

 NaCl + CaCl,. 



Since the alkaline solution contains fewer calcium 

 ions (though the concentration of calcium molecules is the 



'° The sea water was obtained from Woods Hole and was the same as 

 that used in the writer's experiments. 



