5S 
In  determining  the  reaction  rate  it  will  be  seen  that  at  the  hig'hest 
temperature  employed  (37°  C.)  the  number  of  observations  obtain 
able  in  Experiments  i  and  3,  Table  26,  was  limited,  owing  partly  to 
the  rapidity  of  destruction  of  haemoglobin  and  partly  to  the  escape 
of  haemoglobin  from  the  red  cells  into  the  urine  surrounding  them, 
in  consequence  of  which  the  readings  given  by  the  laked  cells  become 
too  low,  and  cease  to  represent  the  actual  destruction.  In  Experiments 
I  to  3,  determinations  of  the  monomolecular  reaction  rate  constant 
show  little  variation  so  long  as  the  amount  of  destruction  of 
haemoglobin  lies  between  20  per  cent,  and  80  per  cent.  Below  the 
lower  limit  destruction  proceeds  more  slowly,  while  above  the  upper 
limit  it  proceeds  more  rapidly.  The  same  variation,  in  greater 
degree,  has  already  been  seen  when  quinine  produces  haemolysis  in 
red  blood  cells  (Tables  13  to  16).  And  as  in  the  latter  case,  so  here, 
if  the  reaction  rate  constant  for  bimolecular  or  multimolecular 
reactions  is  calculated  from  the  data  given,  a  greater  range  of  varia¬ 
tion  is  met  with,  so  that  these  types  of  reaction  are  excluded  from 
consideration.  In  Experiment  4,  in  which  the  reaction  proceeded 
very  slowly,  the  reaction  rate  constant  exhibited  little  variation  when 
the  destruction  exceeded  7  per  cent.  (93  per  cent,  being  left  urn 
altered),  i.e.  after  the  lapse  of  about  two  hours.  If  the  percentages  of 
haemoglobin  are  recalculated  from  the  reaction  rate  constants 
(Columns  4,  8  and  12,  Table  24),  a  fair  agreement  with  the  per¬ 
centages  actually  found  will  be  observed.  It  follows  therefore  that, 
in  the  heterogeneous  system  formed  by  red  blood  cells  suspended 
in  urine,  destruction  of  haemoglobin  proceeds  at  the  same  rate  as  a 
monomolecular  reaction,  except  at  the  beginning  and  end  of  the 
process,  when  slight  delay  and  acceleration  respectively  occur. 
The  values  of  K,  the  monomolecular  reaction  rate  constant, 
obtained  with  the  different  specimens  of  urine  employed,  range 
from  0-0003  to  0-005  at  37°  C.,  from  0-0002  to  0-002  at  3i°C., 
and  from  o-oooS  to  0-0001  at  25°  C.  The  values  obtained  in  urine 
of  specific  gravity  roi5,  whose  reaction  to  litmus  paper  was  alkaline, 
are,  it  will  be  noted,  much  lower  than  those  obtained  in  acid  urine 
of  higher  specific  gravity. 
In  Table  27  the  value  of  the  constant  was  determined  for  each 
of  the  four  specimens  of  urine  employed.  The  values  obtained. 
