Am 'ju°ne.'i903!rm'}    Simple  Forms  of  Laboratory  Apparatus.  259 
The  calcium  chloride  tubes  are  filled  to  one-half  the  height  of  the 
bulb  with  concentrated  sulphuric  acid,  and  the  open  glass  tubes 
closed  with  small  glass  plugs  held  in  short  sections  of  rubber  tubing. 
In  use,  the  Erlenmeyer  flask  is  disconnected,  the  test-tube  re- 
moved and  about  0*5  gramme  of  the  carbonate  to  be  determined 
weighed  into  the  dry  flask ;  sufficient  water  is  then  added  to  cover 
the  lower  end  of  the  capillary  tube  ;  the  test-tube  is  charged  with 
about  4  c.c.  strong  hydrochloric  acid  and  carefully  lowered  into  the 
flask ;  the  cork  carrying  the  calcium  chloride  tubes  is  then  placed  in 
position,  the  apparatus  wiped  with  a  dry  cloth  and  weighed.  Re- 
move the  plug  a  and  incline  the  apparatus  so  that  a  portion  of  the 
hydrochloric  acid  can  escape  from  the  test-tube  and  act  upon  the 
Apparatus  for  the  Estimation  of  Air-drying  Flask. 
Carbon  Dioxide  in  Carbonates. 
carbonate  ;  after  effervescence  ceases,  allow  more  acid  to  run  in,  etc., 
until  finally  all  the  acid  has  been  added.  The  carbon  dioxide  and 
displaced  air  passing  through  the  sulphuric  acid  in  the  calcium 
chloride  tubes  are  thoroughly  dried,  so  that  no  loss  due  to  moisture 
is  to  be  feared. 
Remove  plug  b  and  connect  with  b  of  drying  flask  containing 
about  1  inch  layer  of  sulphuric  acid  ;  in  the  same  way  connect  a  of 
the  apparatus  and  a  of  a  second  drying  flask ;  now  apply  suction  by 
mouth  at  b  end  of  this  last  drying  flask  and  thoroughly  remove  all 
C02  from  the  apparatus  (instead  of  direct  suction,  as  just  stated,  it 
is  much  more  convenient  to  attach  an  aspirator  made  from  a  5-pint 
bottle  and  allow  the  outflowing  water  to  slowly  draw  air  through 
to  the  apparatus);  disconnect  the  apparatus,  replace  plugs,  wipe  and 
