Am.  Jour  Ptiarm  ) 
November,  1904.  I 
Theory  of  Indicators,  etc. 
519 
accompanied  by  a  very  appreciable  increase  in  the  titration  period 
lying  between  the  drops  and  alizarin  end  points  representing  in  all 
probability  the  liberation  of  weak  basic  NH2  groups  presumably  on 
hydrolysis  of  a  union  of  the  type  —  CH2  —  NH  —  CO  —  present 
in  glycyl-glycin  and  other  compounds  of  a  similar  type  investigated 
by  Fischer.  The  action  of  any  hydrolyzing  agent  would  leave 
the  group  —  CH2  —  NH2  free  to  combine  with  any  available 
acid  possessed  of  sufficient  strength  until  equilibrium  were  estab- 
lished. The  period  from  alizarin  to  phenolphthalein  which  very 
probably  represents  a  stronger  NH2  group,  remains  much  more 
constant  until  an  advanced  degree  of  decomposition  is  reached,  at 
which  point  it  increases,  but  not  in  the  same  proportion  as  does  the 
other  period.  Taking  the  total  range  of  titration  from  drops  to 
phenolphthalein,  from  drops  to  alizarin,  from  alizarin  to  phe- 
nolphthalein, total  nitrogen  and  phosphotungstic  nitrogen,  it  will 
be  seen  that  as  the  disgestive  process  advances  all  other  quantities 
increase  in  proportion  to  the  nitrogen,  the  period  from  drops  to 
alizarin  more  rapidly  than  that  from  alazarin  to  phenolphthalein. 
It  is  interesting  to  note  that  the  range  from  alizarin  to  phenol, 
phthalein  compared  with  nitrogen  varies  from  I  :  1 8  to  as  low  as 
I  :  3  or  4,  which  is  in  agreement  with  the  findings  of  Paal.  This 
investigator  prepared  compounds  which  were  practically  HC1  salts 
of  the  products  of  proteid  hydrolysis,  and  from  his  analyses  it  may 
be  calculated  that  the  acid  equivalent  varied  in  proportion  to  the 
nitrogen  from  I  :  1 8  to  I  :  2,  passing  from  relatively  complex  albu- 
moses  to  the  simplest  obtainable  peptones.  This  is  in  agreement 
with  the  findings  of  Latham,  Lieberkiihn  and  others,  who  have  given 
the  soluble  albumoses  a  formula  containing  1 8  atoms  of  nitrogen. 
Osborne,  in  determining  the  acid-combining  equivalent  of  his  crys- 
talline proteid  edestin,  found  two  distinctly  differing  combining 
capacities,  one  which  was  I  :  144  and  the  other  1  :  72,  showing  in 
all  probability  one  weak  and  one  strong  basic  group  free  to  form 
combinations  with  acids. 
IX.  BLOOD  SERUM. 
A  series  of  comparative  titrations  of  the  blood  serum  gives  aver- 
age results  recorded  in  Table  III,  which  are  based  on  the  effect 
exerted  by  1  c.c.  of  clear,  separated  serum  towards  a  variety  of 
indicators.    It  will  be  seen  that  a  fairly  uniform  result  is  obtained 
