24       Densimetric  Estimation  of  Albumin  in  Urine.  {Am'ja(^fimarm' 
DENSIMETKIC  ESTIMATION  OF  ALBUMIN  IN  URINE.1 
By  Zahoe. 
Although  it  has  been  shown  that  from  the  theoretical  side  there 
is  much  to  be  urged  against  the  densimetric  method,  yet  it  is  found 
in  practice,  in  cases  where  accuracy  to  the  first  place  of  decimals  is 
sufficient,  that  the  method  is  extremely  quick  and  handy.  This  is 
felt  nowhere  so  much  as  in  estimations  of  albumin  in  urine,  and  the 
following  method  is  simple,  and  can  be  carried  out  clinically  : — 
The  filtered  urine  is  mixed  with  just  so  much  dilute  acetic  acid  that 
when  it  is  boiled  all  the  albumin  is  coagulated  ;  the  right  proportion 
may  be  ascertained  with  a  small  quantity  of  the  urine  in  a  test-tube 
beforehand.  On  being  filtered  from  the  coagulum,  the  filtrate  should 
give  no  cloudiness  with  acetic  acid  and  potassium  ferrocyanide.  A 
quantity  of  the  urine  is  then  placed  in  a  flask  firmly  closed  with  a  clean 
caoutchouc  stopper.  The  flask  is  hung  for  10  or  15  minutes  in  a 
large  bath,  filled  with  water  kept  boiling.  By  this  means  the  albumin 
is  precipitated.  It  is  then  filtered  off,  the  funnel  leading  through  a 
cork  with  a  hole  in  it  into  a  flask,  and  being  covered  with  a  glass  plate. 
The  density  of  the  urine  and  the  filtrate  is  then  estimated,  not  with  a 
pycnometer  (that  is  unnecessary  for  clinical  work),  but  with  an  arao- 
meter  marked  to  four  places  of  decimals.  Both  fluids  must  be  kept 
at  the  same  temperature.  This  is  best  done  by  placing  them  in  two 
cylinders,  both  immersed  in  a  large  vessel  of  water,  which  should  be 
kept  at  the  same  temperature  if  a  series  of  observations  are  to  be  made. 
The  temperature  of  17#5°  degrees  will  be  found  most  convenient.  The 
difference  between  the  two  specific  gravities  is  then  multiplied  by  400, 
and  the  product  gives  the  number  of  grams  of  albumin  in  100  cc.  of 
urine. 
A  large  number  of  illustrative  experiments  are  quoted,  in  which 
the  approximate  accuracy  of  this  simple  process  is  demonstrated. 
The  number  400  is  the  mean  in  round   numbers  of  the  factor 
100f2    2    »pjie  q uestion  naturallv  arises  why  a  constant  factor 
v{v2  —  Vly  J  J 
should  give  such  good  results  in  albuminous  urine,  when  not  onlytheo- 
1  Zeit.  physiol.  Chem.,  xii.,  484-495  ;  reprinted  from  Jour.  Chem.  Soc,  Nov.,  p* 
1227. 
2  v  is  spec.  grav.  of  the  urine  ;  v2,  spec.  grav.  of  the  proteids  ;  v1}  spec.  grav. 
of  urine  minus  proteids. 
