8l2 
Book  Reviews. 
(  Am.  Jour.  Pharm. 
\       Nov.,  1921. 
1854  were  of  great  importance,  leading  to  the  introduction  of  the 
terms  "crystalloid"  and  "colloid"  and  to  the  process  of  dialysis. 
"Colloid  chemistry"  has  become  a  most  important  branch  of  the 
science. 
It  is  interesting  to  note  that  Pfeffer  was  a  botanist,  and  that 
his  studies  were  determined  by  his  interest  in  the  physiology  of  the 
living  cell.  It  was  Pfeffer  who  made  the  ingenious  improvement 
by  which  the  membrane  was  able  to  sustain  a  high  pressure.  The 
highest  osmotic  pressure  will  be  obtained  when  the  membrane  is 
permeable  by  the  dissolving  medium  (solvent)  and  not  by  the  dis- 
solved substance  (solute).  Pfeffer  employed  a  porous  cup  in  the 
walls  of  which  copper  ferrocyanide  was  produced  by  the  diffusion 
of  copper  sulphate  and  potassium  ferrocyanide  from  opposite  sides. 
This  pot  was  connected  with  a  manometer  tube.  Naturally,  this 
early  apparatus  was  not  entirely  satisfactory,  and  improvements 
have  been  made  so  to  secure  greater  accuracy,  yet  Pfeffer's  results 
remained  for  a  long  time  the  principal  data,  being  indeed,  the  only 
quantitative  measurements,  and  produced  a  deep  effect  on  the  his- 
tory of  the  chemistry  and  physics  of  solutions. 
The  publisher  presents  in  the  present  volume,  as  already  noted, 
an  exact  reprint  of  the  original  work,  which  appeared  in  1876,  ex- 
cept addition  of  a  note  by  Dr.  F.  Czapek.  Reference  is  made  in 
this  introduction  to  the  important  additions  to  the  knowledge  of  the 
physical  chemistry  of  solution  by  H.  N.  Morse  and  his  co-workers 
in  the  laboratory  of  the  Johns  Hopkins  University.  An  account  of 
these  investigations  appeared  in  pamphlet  form  in  1914,  under  the 
title  of  "The  Osmotic  Pressure  of  Aqueous  Solutions."  The  ex- 
tensive studies  since  made  in  this  field  are  familiar  to  physical 
chemists. 
The  book  itself  is  well  printed  and  is  an  interesting  contribu- 
tion to  the  classics  of  chemistry.  Physical  chemical  phenomena 
received  but  scant  notice  in  the  manuals  of  physics  or  chemistry 
in  the  days  when  Dutrochet,  Graham,  Pfeffer  and  many  others  were 
working,  and  the  topic  first  made  its  appearance  in  manual  of  chem- 
istry as  "chemical  physics,"  but  now  it  forms  the  subject  of  inde- 
pendent manuals  and  has  a  large  part  in  the  literature  of  the  sci- 
ence. 
The  firm  of  Wilhelm,  Englemann  deserves  the  thanks  of  chem- 
ists for  re-issuing  this  important  and  interesting  contribution,  the 
