MANUFACTURE  OF  AMMONIA,  ETC. 
231 
the  acid  liquor  of  the  lower  cistern  is  continually  forced  by  suit- 
able means  into  the  upper  perforated  cistern,  the  ammonia  in  its 
passage  upwards  comes  into  contact  with  the  acid  trickling  down 
through  the  column,  and  is  thus  presented  from  passing  off  with 
the  other  products  of  combustion,  which  are  conveyed  by  an 
exit-pipe  into  the  chimney.  When  the  acid  liquor  has  become 
neutralized  by  ammonia,  it  is  drawn  off,  filtered,  evaporated,  and 
crystallized,  a  fresh  supply  of  acid  being  placed  in  the  lower 
cistern. 
Mr.  Laming  patented,  August  12th,  1852,  the  following  method 
of  manufacturing  sulphate  of  ammonia  from  the  ammoniacal 
liquors  of  gas-works.  The  ammonia  is  first  separated  in  its 
simple  form,  or  as  carbonate  of  ammonia,  by  any  known  means, 
after  which  it  is  converted  into  sulphate  of  ammonia,  by  causing 
streams  of  sulphurous  acid  to  be  brought  into  contact  with  it, 
and  the  sulphite  of  ammonia  is  finally  converted  into  sulphate 
by  exposing  it  to  the  combined  influences  of  atmospheric  air  and 
water. 
Dr.  Ure,  in  his  Dictionary  of  Arts  and  Manufactures,  states 
that  7200  gallons  of  ammoniacal  gas-liquor  treated  with  4500 
lbs.  of  sulphuric  acid,  sp.  grav.  1625,  produces  2400  gallons  of 
solution  of  sulphate  of  ammonia,  of  sp.  grav.  1150.  As  a  gallon 
of  solution  of  ordinary  sulphate  of  ammonia,  of  the  above  strength, 
contains  three  pounds  of  crystallized  sulphate,  it  follows  that  in 
the  above  case  the  product  is  at  the  rate  of  one  pound  per  gallon 
of  gas-liquor,  which  is  almost  double  the  quantity  ordinarily  ob- 
tained. 
The  quantity  of  ammoniacal  liquor  obtained  at  one  of  the  Lon- 
don gas-works,  during  one  year,  from  the  distillation  of  51,100 
tons  of  coal,  was  224,800  gallons. 
Ammonia  Meter, — In  order  to  determine  the  strength  of  any 
given  solution  of  ammonia,  Mr.  J.  J.  Griffin,  of  Baker  street, 
has  constructed  a  useful  instrument,  termed  an  ammonia  meter, 
This  instrument  is  founded  on  the  following  facts  :  That  mix- 
tures of  liquid  ammonia  with  water  possess  a  specific  gravity, 
which  is  the  mean  of  the  specific  gravities  of  their  components  ; 
that  in  all  solutions  of  ammonia,  a  quantity  of  anhydrous  ammo- 
nia, weighing  212 1  grains,  which  he  calls  a  test-atom,  displaces 
300  grains  of  water,  and  reduces  the  specific  gravity  of  the 
