ELECTROLYTES AND THEIR ACTION 



obtained will be found 

 in the paper by Pride- 

 aux on p. 125. The 

 values may also be 

 read on the curves of 

 Fig. 58, copied from 

 this paper. The ab- 

 scissse give the number 

 of c.c. of molar sodium 

 hydroxide to be added 

 to 10 c.c. of molar 

 phosphoric acid to 

 make 100 c.c. of solu 

 tion, in order that we 

 may have a hydrogen 

 ion concentration of 

 the ordinate selected. 

 The second part of the 

 figure on the succeed- 

 ing page is the steeper 

 parts of the complete 

 curve drawn on a 

 larger scale, so that 

 greater accuracy may 

 be attained by prepar- 

 ing a larger volume of 

 the solution, say a litre. 



To illustrate the use 

 of the curve : Suppose 

 that a solution of the 

 optimal acidity for emul- 

 sin is required. This is, 

 according to Vulquin 

 (1911), ox 10- 6 in H- ions. 

 The exponent of 10 which 

 we require is log. 5 minus 

 6 times log. 10=-5'39. 

 Corresponding to this or-' 

 dinate in the table we find 

 ID'S; we must, therefore, 

 add 10'8 c.c. of molar 

 NaOH to 10 c.c. of molar 

 phosphoric acid and dilute 

 to 100 c.c. 



PHYSIOLOGICAL 



SALINE 

 SOLUTIONS 



In the case of 

 organisms whose cells 

 are unprotected by a 

 resistant envelope, it 

 has been already 

 pointed out that the 

 solutions which bathe 

 them must have the 

 same osmotic pressure 

 as the cell contents. 

 Otherwise the cell will 

 contract or expand, 

 by the loss or gain of 

 water, until its osmotic 



