1 68  Modification  of  Nessler  s  Tube.       { AmAp?ii"iSarm- 
The  "  Nessler  "  jar  used  in  the  above  analysis  is  about  6  inches 
in  length,  but  a  jar  designed  by  Hehner,  containing  IOO  c.c,  with  a 
stopcock,  is  also  on  the  market.  The  Hehner  tube  is  too  wide  and 
costs  entirely  too  much.  The  objection  to  the  diameter  of  these  two 
jars  is  overcome  by  the  tube  mentioned  below,  which  is  the  same  as 
that  of  the  one  devised  by  Dr.  Leffmann.  This  jar  is  very  much  more 
delicate  in  colorimetric  work  than  the  shorter  jars  (50  c.c.)  in  use  in 
many  laboratories. 
The  jar  (which  is  illustrated  in  an  accompanying  cut)  is  12  inches 
in  length,  ^  inch  in  diameter,  about  9  inches  from  base  to  top 
mark  (50  c.c),  and  graduated  in  5  c.c.  with  dashes  for  the  I  c.c. 
graduations.  There  is  a  small  tube  projecting  from  the  side  at  the 
base,  which  may  be  either  plain  or  have  a  stopcock.  A  number  of 
plain  tubes  similar  to  the  above  (50  c.c.  graduation)  are  necessary 
to  collect  the  distilled  ammonia. 
The  method,  originated  by  Professors  Chester  and  Robin,  of  using 
this  side-necked  "  Nessler  "  jar,  consists  of  connecting  the  side  tube 
with  a  burette  by  a  small  rubber  tube.  The  three  tubes  of  free  and 
albuminoid  ammonia  are  collected  from  the  condenser  and  "  nessler. 
ized  "  in  the  usual  manner  and  mixed  together,  causing  a  similar 
shade  in  each.  One  of  these  tubes  is  placed  beside  the  one  con- 
necting with  the  burette  containing  the  standard  ammonia  solution, 
and  moved  with  a  vertical  movement.  The  liquid  in  the  standard 
column  is  made  to  increase  and  decrease  at  will,  and  the  number  of 
cubic  centimetres  is  always  visible. 
The  cost  of  the  small  "  Nessler  "  jars  now  in  use  is  50  cents, 
while  the  Hehner  tube  costs  $4.50.  The  Leffmann  tube  with  the  sin- 
gle graduation  can  be  obtained  for  75  cents,  although  we  have  had 
them  manufactured  for  40  cents.  The  jars  with  the  side  neck  cost 
$1.75,  and  the  one  with  the  stopcock  costs  $2.50. 
