454 
Theory  of  Indicators,  etc. 
J  Am.  Jour.  Pharm. 
\     October,  1904. 
ously  militated  against  proper  correlation  and  utilization  of  these 
results  has  been  the  promiscuous  employment  of  widely  differing 
types  of  indicators,  with  the  result  that  the  figures  obtained  by  dif- 
ferent investigators  are  seldom  comparable.  When,  therefore,  a 
series  of  experiments  was  commenced  in  this  laboratory  with  the 
object  of  affording,  so  far  as  possible,  a  clear  insight  regarding  the 
nature  of  the  disturbances  in  metabolism  taking  place  in  cancer  and 
allied  conditions,  it  became  necessary  to  systematize  existing  methods 
or  adopt  new  ones.  A  careful  consideration  of  the  published  work 
of  clinicians,  in  so  far  as  chemical  analyses  are  concerned,  makes  it 
apparent  that  the  empirical  results,  more  or  less  dependent  upon  the 
individual  who  obtains  them,  are  fairly  satisfactory  so  far  as  he 
personally  is  concerned,  but  are  possessed  of  little  scientific  value. 
More  especially  is  this  the  case  when  volumetric  methods  of  analysis 
are  employed,  probably  owing  to  the  failure  of  the  majority  of 
workers  in  this  field  to  fully  appreciate  the  significance  of  the  end- 
points  of  individual  indicators  or  the  nature  of  the  extremely  deli- 
cate problems  in  chemical  equilibrium  with  which  they  have  to 
deal.  The  principal  object  of  this  preliminary  paper  is  to  clearly 
outline  the  nature  of  the  various  classes  of  indicators  used  in  aci- 
dimetry  and  alkalimetry ;  to  study  their  behavior  towards  various 
weak  bases  and  acids  which  may  occur  in  the  course  of  physiological 
work ;  further,  to  make  a  series  of  tests  on  artificial  and  normal 
stomach  contents,  pancreatic  digests,  blood  serum,  etc.,  all  as  an 
introduction,  so  to  speak,  to  subsequent  publications  dealing  with 
pathological  conditions  such  as  are  met  with  in  cancer  of  the 
stomach,  the  blood  of  cachectic  cancer  patients,  etc. 
Incidentally  it  may  be  remarked  that  work  of  this  nature  can  be 
utilized  to  throw  light  on  the  constitution  of  the  proteid  molecule 
and  the  numerous  products  resulting  from  the  various  stages  of 
peptic  or  tryptic  digestion,  or  from  the  intervention  of  bacteria  and 
abnormal  enzymes. 
II.  REGARDING  THE  NATURE  OF  INDICATORS  AND  THEORY  OF  THEIR 
ACTION. 
The  indicators  employed  may  be  divided  into  three  more  or  less 
artificial  groups : 
(i)  Those  which  are  especially  sensitive  to  alkalies,  as,  for  exam- 
ple, benzo-purpurin,  congo-red  and  lakmoid,  and  may  consequently 
be  employed  for  titrating  very  weak  bases. 
