494  Volumetric  Estimation  of  Urea.        {Am' octT,\^&vm' 
NEW  METHOD  FOR  THE  VOLUMETRIC  ESTIMATION 
OF  UREA. 
By  Dr.  G.  Campari. 
Translated  from  "Annali  di  Chim."  1887,  page  156,  by  Jos.  W.  England,  Ph.  G. 
This  method  is  based  upon  the  decomposing  action  exercised  by 
nitrous  acid  upon  urea  to  form  carbonic  anhydride,  nitrogen  gas  and 
water.  In  a  glass  flask  of  about  200  ec.  capacity,  place  20  cc.  of  a  10 
percent,  solution  of  nitrite  of  potassium,  then  2  cc.  of  the  urine,  or  of  the 
liquid  containing  the  urea,  and  then  2  cc.  of  a  5  per  cent,  solution  of 
sulphuric  acid  (or  1  cc.  of  the  diluted  sulphuric  acid  of  the  U.  S.  P., 
1880).  After  the  addition  of  the  acid,  through  the  safety  tube,  con- 
duct the  evolved  gases  through  the  other  tube  alongside,  descending 
into  a  flask  containing  110  cc.  of  lime-water.  Warm,  very  slightly, 
the  urea  containing  flask,  so  that  the  reaction  takes  at  least  fifteen 
minutes  time.  When  the  connecting  tube  becomes  warm,  from  hot 
aqueous  vapor,  the  operation  is  at  an  end  and  the  lime  solution 
should  be  removed  at  once. 
Now  measure  10  cc.  of  this  liquid,  turbid  with  its  suspended  cal- 
cium carbonate  and  color  rose-violet,  with  a  drop  of  an  alcoholic  solu- 
tion of  phenol-phthaleme  and,  first,  determine  the  number  of  cc.  of  a 
solution  of  oxalic  acid,  containing  3*15  gm.  to  the  liter,  that  are 
needed  to  neutralize  the  10  cc.  of  the  liquid.  Then  multiply  the 
volume  of  the  oxalic  acid  solution  used  by  0*0165  and  subtract  the 
product  from  the  number  0*15  ;  the  difference  indicates  the  amount  of 
urea  contained  in  the  2  cc.  of  urine,  or  the  urea  containing  liquid 
examined. 
Pavesi  and  Rotondi  have  found  that  1  cc.  of  lime-water  is  neutral- 
ized by  0*00241  gm.  of  tartaric  acid  ;  therefore  every  cc.  contains 
0*001273  gm.  of  CaO,  and  110  cc.  of  lime-water  should  then  contain 
0*14003  of  CaO ;  corresponding  to  0*15  gm.  of  urea.  The  chemical 
reactions  of  this  new  process,  are  as  follows,  first  : 
CO  (ra2)2+2  OT02=3  H20+4  N+C02  . 
Urea,  60  94         54       56  44 
Secondly : 
CaO-j-C02=CaC03 
56     44  100 
Now  since  44  gm.  of  C02  are  equivalent  to,  or  neutralize,  56  gm. 
CaO,  then  56  gm.  of  CaO  are  equivalent  to  60  gm.  of  CO  (NH2)2,  for 
60  gm.  of  CO(NH2)2  yield  44  gm.  of  C02  (as  seen  in  the  first 
