22 Diffusion and Osmotic Peessuee 



equivalent" and "gram-molecule" are synonymous terms 

 in the case of monovalent compounds, and that a gram- 

 equivalent of a bivalent compound is one half of its gram- 

 molecule, of a trivalent compound one-third, etc. 



A solution made up so as to contain in one liter a single 

 gram-equivalent of solute is termed an equivalent normal, 

 or simply a normal, solution. Unfortunately there is a usage 

 which terms a molecular solution normal, thus giving rise 

 to ambiguity for all but monovalent solutes. This ambi- 

 guity can be avoided only by the careful definition of the 

 term "normal" by each author using it.' For all neutral 

 organic compounds, such as the sugars, and also for monova- 

 lent electrolytes, a gram-equivalent is the same as a gram- 

 molecule, and a normal solution must be a gram-molecule in 

 a liter volume. Thus the sugar solutions described in a pre- 

 vious paragraph are both normal solutions. No ambiguity 

 can arise from the use of the term in reference to such com- 

 pounds. 



Kegarding acid salts (such as KHSO4, for example), there 

 is a difference of opinion as to what should be denoted by 

 gram-equivalent. Some hold (e. g., Kahlenberg) that in 

 the salt just mentioned gram-equivalent and gram-molecule 

 are identical. Thus, such a salt might be regarded as a 

 monobasic acid. On the other hand, Sutton, Fresenitis, 

 Dandeno, and others regard a gram-equivalent of KHSO^ 

 as one-half a gram-molecule. Thus, an equivalent solution 

 of this salt would contain only one-half gram of hydrogen; 

 the salt is to be regarded as a monobasic acid, one-half of 

 whose hydrogen has been replaced. It seems that the latter 

 is the more truly scientific position. 



1 For an aooonnt of confusion (partly imagined) which has arisen from a lack of 

 attention to such definition of these terms, see J. B. Dandeno, " The Application of 

 Normal Solutions to Biological Problems," Bo«. (?o2.. Vol. XXXII (1901), pp. 229-37. 

 Also see "Open Letters," one from LoDis Kahlenbeeq, and an answer from Dan- 

 deno, ibid., p. 437. 



