524 
Theory  of  Indicators,  etc. 
(  Am.  Jour.  Pharm 
1  November,  1904. 
glucinvanillin,  are  entirely  unaffected.  After  allowing  for  the  influ- 
ence due  to  carbonic  acid,  it  is  found  that  the  range  of  titration 
increases  with  increasing  digestion,  being  at  the  early  stages  more 
or  less  proportionate  to  the  amount  of  proteid  brought  into  solution 
as  estimated  by  the  total  nitrogen,  but  subsequently  increasing  in 
undue  proportion  to  the  total  nitrogen  as  digestion  proceeds,  with 
the  formation  of  simpler  nitrogenous  products. 
The  bearing  which  work  of  this  nature  may  have  on  the  solution 
of  certain  problems  connected  with  the  constitution  of  proteids  and 
their  decomposition  products  was  also  discussed.  Titrations  of  nor- 
mal blood  serum  showing  a  wide  variation  with  different  indicators 
which  could  not  possibly  be  attributed  to  the  inorganic  constituents 
of  the  serum  were  tabulated  and  the  necessity  of  an  agreement  upon 
certain  specific  indicator  end  points  for  serum  titration  emphasized. 
The  titration  results  on  urine  were  shown  to  be  fairly  dependent 
on  the  amount  of  phosphates  present,  the  small  proportion  of  amido 
bases  and  weak  acids  present  exerting  a  relatively  small  effect  in 
normal  cases.  A  normal  urine  should  be  acid  to  phenolphthalein 
and  alkaline  to  alizarin,  the  end  point  lying  somewhere  between  the 
neutralization  points  of  these  indicators.  In  other  words,  whilst 
the  first  acid  group  of  the  phosphates  should  be  neutralized,  the 
third  acid  group  should  remain  free,  varying  proportions  of  the  sec- 
ond group  being  neutralized  or  not,  according  to  the  state  of  equi- 
librium of  the  system.  Naturally,  in  the  presence  of  any  consider- 
able quantity  of  ammonia  which  in  contradistinction  to  urea  exerts 
a  powerful  effect  upon  alizarin  and  phenolphthalein,  the  urine 
would  be  less  acid,  or  even  alkaline  to  phenolphthalein  and  more 
strongly  alkaline  to  alizarin  than  is  normally  the  case. 
In  conclusion,  a  plea  must  be  raised  for  the  establishment  of  a 
more  accurate  standard  of  titration  of  various  types  of  physiological 
solutions,  definite  indicators  with  definite  end  points  being  em- 
ployed, so  that  the  work  of  various  investigators  may  be  in  some 
sense  comparable,  in  order  that  the  results  ol  volumetric  analyses 
may  have  their  scientific  value  when  used  in  conjunction  with  the 
more  exact  gravimetric  and  physico-chemical  methods,  which  can 
scarcely  be  said  to  possess  as  wide  an  application. 
LITERATURE. 
Fischer,  Emil.    Sitzungsber.    Kgl.  pr.  Akad.  Wiss.    Berlin,  p.  387.  1903. 
(Chem.  Centralbl.    Vol.  I,  p.  1303.  1903.) 
