NITRATE  OF  AMMONIA  AND  NITROUS  OXIDE. 
413 
Directions  for  setting  up. 
Place  the  holder  in  a  level  position,  and  fill  it  with  water  to  within  an 
inch  or  two  of  the  lower  edge  of  the  taper  rim. 
A  piece  of  lime  the  size  of  an  egg  will  help  to  keep  the  water  pure. 
Now  open  all  the  spigots,  especially  the  one  in  the  top  of  the  receiver, 
and  gently  sink  it  into  the  water  ;  then  close  the  spigot  in  the  top  of  the 
receiver  and  that  on  the  upper  edge  of  the  holder,  and  arrange  the  weights 
that  are  attached  to  the  receiver. 
Put  into  the  first  jar  (No.  1)  about  a  pint  of  water.  Into  the  second 
jar  (No.  2)  such  an  amount  of  water  that  the  long  pipe  attached  to  the 
lid  shall  dip  about  one  inch  below  i^s  level ;  then  add  a  half  teuspoonful 
of  sulphuric  acid  (oil  of  vitriol)  and  about  a  quarter  pound  sulphate  of 
iron  (copperas).  Into  the  third  jar  (No.  3)  put  a  like  quantiiy  of  water, 
and  add  a  couple  of  sticks  of  caustic  potash. 
Arrange  the  jars  in  line  and  connect  them  by  tubing,  as  shown  in  the 
cut.  The  tube  from  the  retort  must  connect  with  the  long. pipe  of  jar 
No.  1,  and  so  on.  When  properly  arranged,  a  current  of  air  blown  into 
the  tube  intended  to  connect  with  the  retort  will  cause  the  water  to  bubble 
in  jars  Nos.  2  and  3,  and  if  the  spigot  to  which  No.  3  is  attached  be  open, 
the  receiver  will  begin  to  rise. 
Put  into  the  retort  the  quantity  of  [nitrate  of]  ammonia  intended  to  be 
used  (1  lb.  will  make  about  30  gallons  of  gas). 
Place  the  sand-dish  upon  the  stove,  with  sand  sufficient  to  protect  the 
retort.  Connect  the  long  pipe  of  the  first  jar  to  the  retort  by  rubber 
tubing,  so  that  the  condensed  steam  may  run  into  it. 
Now  apply  the  heat  gradually,  and  watch  the  process,  being  careful 
not  to  overheat  the  ammonia  [salt]. 
The  heat  should  be  shut  off  before  the  [nitrate  of]  ammonia  is  quite  all 
decomposed,  in  order  to  avoid  breaking  the  retort;  and  before  the  gas 
has  quite  ceased  to  come  over,  the  retort  should  be  disconnected  from  the 
first  jar,  and  the  receiving  spigot  closed.  This  is  an  essential  point,  for 
if  not  attended  to  promptly,  and  the  atmospheric  pressure  thus  equalized, 
the  solutions  will  be  forced  from  one  jar  to  another  and  into  the  retort, 
in  consequence  of  the  partial  vacuum  created  by  the  withdrawal  of  the 
heat. 
It  will  be  understood  that  the  first  jar  is  merely  to  receive  the  drip  ; 
the  use  of  the  water  is  simply  to  keep  the  jar  cool,  and  the  tendency  to 
become  overheated  maybe  obviated  by  setting  it  in  a  vessel  of  cold  water. 
Fresh  water  may  be  substituted  at  each  operation. 
The  solution  of  copperas  should  be  renewed  when  it  loses  its  green 
color,  and  the  potash  solution  when  it  loses  its  alkalinity,  as  shown  by  its 
not  turning  red  test-paper  blue. 
The  inhaling  tube  is- attached  to  the  top  spigot  of  the  holder. 
The  register  indicates  the  number  of  gallons  of  gas  in  the  holder,  as 
well  as  the  quantity  inhaled. 
