Am.  Jonr.  Ptaarm.  \ 
August,  1902.  J 
Gasometrtc  Analysis. 
391 
siphon-tube  can  and  must  be  perfectly  filled  with  water,  although  it 
is  not  necessary  to  have  d  perfectly  filled  ;  connect  the  two  bottles 
at  c  and  remove  the  siphon-tube  from  the  vessel  containing  water ; 
see  that  the  apparatus  does  not  leak  by  watching  the  siphon-tubt ; 
should  this,  by  a  slow  dropping  of  water,  indicate  a  leak,  this  can 
generally  be  stopped  by  pouring  a  little  water  over  the  corks ;  place 
the  siphon-tube  in  the  vessel  used  to  collect  or  measure  the  water 
displaced  by  the  gas  evolved  in  the  experiment ;  if  this  vessel  is 
graduated  it  should  be  dry  at  the  beginning  of  the  experiment;  it, 
on  the  other  hand,  it  is  not  graduated,  rinse  it  with  a  little  water 
and  allow  to  drain  before  using.  By  this  precaution  the  quantity  of 
water  used  to  moisten  the  vessel,  and  which  would  be  lost  in  trans- 
ferring to  a  graduated  vessel,  is  first  added. 
(3)  In  handling  the  apparatus,  as  in  connecting  and  agitating, 
hold  the  bottles  at  the  lip,  so  as  to  take  advantage  of  the  thickest 
portion  of  the  glass  as  a  nonconductor  of  heat,  and  prevent  expan- 
sion of  the  air  or  gas  by  the  heat  of  the  hand. 
(4)  After  the  apparatus  has  been  adjusted  and  prepared  for  a 
determination,  a  record  must  be  kept  of  the  liquids  allowed  to  enter 
through  the  funnel-tube,  and  this  volume  subtracted  from  the  volume 
of  the  displaced  water  to  obtain  the  volume  of  the  evolved  gas ;  it 
is,  therefore,  important,  in  introducing  a  definite  quantity  of  solution, 
to  see  that  there  is  still  the  same  quantity  of  liquid  in  the  funnel- 
tube  as  at  the  beginning  of  the  determination ;  should  the  liquid  go 
below  the  adjustment  at  b,  more  than  the  intended  quantity  of  liquid 
will  enter.  In  agitating  after  the  addition  of  the  reacting  substances, 
this  should  not  be  so  violent  as  to  throw  the  liquid  in  g  against  the 
cork,  because  some  of  the  liquid  escaping  through  c  into  d  will  be 
so  diluted  by  the  water  as  to  stop  the  reaction,  and  some  of  the 
liquid  in  the  funnel-tube  will  react  with  the  material  in  g  (one  of 
these  entails  loss  of  reacting  substance,  the  other  increases  the 
same). 
Estimation  of  Urea. — Place  40  c.c.  Labarraque's  Solution  in  gener- 
ator g;  adjust  the  funnel-tube  with  urine.  Add  4  c.c.  urine  through 
funnel-tube ;  agitate  until  effervescence  ceases  and  allow  to  stand 
10  to  15  minutes;  measure  the  displaced  water,  subtract  4  c.c.  and 
multiply  remainder  by  0-002686  for  the  quantity  of  urea  in  4  c.c. 
To  obtain  the  percentage,  multiply  the  number  of  cubic  centimeters 
of  urine  taken  by  the  specific  gravity,  then  the  resulting  weight  of 
urine  taken  :  weight  ot  urea  found  ^h-  100  :  x. 
