842 
Book  Reviews. 
I  Am.  Jour.  Pharm. 
\   November,  1920. 
with  all  other  notable  theories  or  principles  in  science,  foreshadow- 
ings  of  some  features  of  it  can  be  found  in  the  works  of  earlier  scien- 
tists, but  it  is  not  the  one  who  first  "thinks  of"  anything,  but  the 
one  who  "thinks  it  out"  or  establishes  it  that  deserves  the  greater 
honor.  Dr.  Clark  informs  us  in  his  preface  that  Pasteur  had  a  dis- 
tinct perception  of  the  importance  of  the  degree  of  acidity,  although, 
of  course,  he  did  not  formulate  this  in  the  terms  of  dissociation  or 
ion  concentration.  Pasteur  pointed  out,  in  his  Studies  on  Fermenta- 
tion, that  the  relatively  high  acidity  of  must  favors  a  natural  alco- 
holic fermentation,  while  the  low  relative  acidity  of  wort  intro- 
duces difficulties  in  the  brewing  of  malt  liquors.  There  is  here 
probably  a  theme  for  an  interesting  and  useful  disquisition  on  the 
influence  of  hydrogen  ion  concentration  on  the  progress  of  civiliza- 
tion. One  writer  has  declared  that  the  limits  of  the  Roman  Empire 
in  northwestern  Europe  were,  in  a  measure  at  least,  determined  by 
the  food  and  beverage  habits  of  the  races.  The  Romans  and  their 
principal  auxiliaries  were  accustomed  to  wine  and  olive  oil;  the 
tribes  of  Baltic  region  used  beer  and  butter.  We  have  good  reason 
to  believe  that  butter  is  more  nutritious  than  the  vegetable  oils. 
The  materialistic  conception  of  history  has  been  a  prominent  theme 
in  later  days;  is  it  possible  that  the  world's  progress  and  the  solution 
of  the  problem  of  the  league  of  nations  will  be  reduced  finally  to  an 
equation  involving  log.  P^? 
We  are  dealing,  however,  with  a  work  of  special  type  and  of 
novel  purpose.  Chemists  have,  at  last,  the  important  and  difficult 
problems  of  hydrogen  ion  concentration  presented  in  extended  and 
careful  manner  and  explained  in  detail.  Dr.  Clark  points  out  that 
of  all  the  secondary  inferences  drawn  from  the  general  theory  of 
ionization,  the  most  important  is  that  relating  to  the  resolution  of 
"acidity"  into  two  components — the  concentration  of  hydrogen  ions 
and  the  quantity  of  acid  capable  of  furnishing  those  ions.  For 
two  reasons  the  concentration  of  the  hydrogen  ion  occupies  a  unique 
place  in  the  phenomena  of  ionization.  The  factor  of  concentration 
is  now  known  to  be  of  very  great  importance  in  biologic  chemistry. 
Already,  many  data  have  been  collected  as  to  the  extent  which  the 
soil  acids  are  ionized,  and  in  this  connection,  it  must  be  noted  that 
the  older  methods  which  merely  determined  the  total  acidity  by 
titration,  for  instance,  with  alkali,  do  not  give  the  real  reaction  of 
the  soil  solution  to  the  living  tissues  with  which  they  are  in  contact. 
It  is  a  question,  indeed,  whether,  in  the  light  of  the  development  of 
