Am.  Jour.  Pharnt.) 
Dec,  1884.  J 
Tests  for  Albumen  in  Urine. 
639 
as  a  check  upon  the  picric  acid  test,  when  small  quantities  of  albumen 
only  were  present,  and,  until  lately,  had  not  thought  of  applying  it 
to  normal  urine.  I  now  find,  however,  that  this  test-liquid,  when 
acidulated — as  it  must  be,  to  act  at  all — gives  a  distinct  opalescence 
in  most,  if  not  all,  normal  urines.  I  find,  too,  that  after  the  mucin 
has  been  removed  from  normal  urine  by  its  coagulation  with  acetic  or 
citric  acid,  and  subsequent  filtration,  the  addition  of  the  potassio- 
mercuric  iodide  to  the  filtrate  causes  a  decided  opalescence,  which  is 
probably  due  to  the  precipitation  of  some  substance  other  than  mucin 
in  the  urine. 
In  testing  urines  which  contain  a  mere  trace  of  albumen,  it  is 
important  to  remove  any  turbidity  that  would  interfere  with  the  pro- 
cess. Urates  would  be  removed  by  heat,  suspended  mucus  and  other 
particles  by  filtration.  The  addition  of  the  picric  acid  solution  to  a 
turbid  specimen  might  give  a  fallacious  appearance  of  coagulated 
albumen,  when,  in  fact,  there  is  nothing  more  than  some  increased 
opacity,  due  to  the  yellow  staining  of  the  suspended  particles. 
Picric  acid  is  itself  sufficiently  acid,  when  added  in  excess,  to 
dissolve  and  clear  a  phosphatic  turbidity.  In  the  rare  case  of  the  urine 
being  so  highly  alkaline  as  to  prevent  the  coagulation  of  the  albumen 
by  an  excess  of  picric  acid,  the  plan  is  to  add  sufficient  citric  or  acetic 
acid  to  neutralize  the  alkali,  then  to  filter,  and  add  the  picric  acid  to 
the  filtrate. 
It  appears,  then,  that  picric  acid  as  a  test  for  albumen  is  more  free 
from  fallacy  than  any  other,  not  even  excepting  heat  and  nitric  acid, 
which  Dr.  Roberts  expresses  his  determination  to  fall  back  upon.  Of 
course,  in  a  doubtful  case,  no  one  would  neglect  to  apply  more  than 
one  test.  That  picric  acid  is  a  more  sensitive  test  than  heat  and  nitric 
acid  is  easily  proved  by  taking  a  highly  albuminous  specimen  and 
gradually  diluting  it  up  to  the  point  where — though  these  tests  fail  to 
detect  it — picric  acid  still  gives  a  distinct  reaction. 
The  main  advantages  of  picric  acid  as  a  test  for  albumen  are  the 
following: — It  instantly  detects  a  ^mall  amount  of  albumen  which 
nitric  acid  would  indicate  only  slowly  or  not  at  all ;  while,  on  the  one 
hand,  an  insufficient  addition  of  the  test  does  not,  as  is  the  case  with 
nitric  acid,  prevent  the  subsequent  coagulation  by  heat ;  neither,  on 
the  other  hand,  does  an  excess  of  picric  acid  redissolve  the  precipitate, 
as  does  an  excess  of  nitric  acid.  For  bedside  urinary  testing,  the 
portability  of  the  innocuous  powder  is  a  great  convenience.    The  fact 
