48 
GAS  FURNACE  FOR  GENERAL  CHEMICAL  USE. 
increased,  and  then  the  supply  of  air.  In  short,  to  prevent  the 
flame  blowing  down,  the  gas  must  always  be  first  placed  in  ex- 
cess, and  then  have  the  proper  quantity  of  air  adjusted  to  suit 
it  by  means  of  the  regulator  c. 
Arrangement  for  Boiling  and  Evaporation. — Fig.  3  represents 
this  gas  furnace  arranged  for  boiling  and  evaporation,  a  is 
the  gas-burner,  Fig.  1  ;  6,  an  iron  stool  with  three  legs  ;  c,  a 
furnace  body,  or  iron  jacket,  lined  with  plumbago  or  fire-clay. 
Fig.  4  shows  the  jacket  and  lining  in  section,  and  marks  the 
position  of  the  fire-box,  d,  of  the  gas-burner.  This  furnace  is 
14  inches  high,  and  9  inches  in  diameter.  The  three  brackets 
fixed  on  the  upper  part  of  the  jacket  serve  to  support  the  vessel 
that  contains  the  liquid  that  is  to  be  boiled  or  evaporated.  A 
porcelain  basin  of  16  or  18  inches  in  diameter  can  be  thus  sup- 
ported. It  is  important  to  allow  between  the  jacket  c  and  the 
evaporating  basin  plenty  of  space  for  the  escape  of  heated  air, 
which  ascends  from  the  interior  of  the  furnace.  When  the 
evaporating  basin  is  of  small  diameter,  it  may  be  supported  on 
iron  triangles,  placed  in  the  furnace  e.  Fig.  4  shows  that, 
around  the  vertical  tube  of  the  gas-burner,  a,  there  is  in  the 
bottom  of  the  furnace,  c,  a  circular  opening,  which  is  of  2  inches 
diameter,  and  through  which  air  passes  freely,  partly  to  feed  the 
flame  and  partly  to  be  heated  by  the  flame,  and  be  directed  up- 
wards in  a  continuous  current  upon  the  lower  surface  of  the 
basin  that  is  to  be  heated.  The  flame  within  the  furnace  burns 
steadily.  No  side  currents  of  air  agitate  it.  No  part  of  it 
touches,  or  must  be  permitted  to  touch,  the  basin,  which  should 
receive  its  heat  solely  from  the  mass  of  ascending  hot  air.  The 
gas-burner  thus  arranged,  and  supplied  by  a  gas-pipe  of  \  inch 
bore,  burns  about  33  cubic  feet  of  gas  in  an  hour,  and  the  flame 
which  it  produces,  acting  upon  water  contained  in  an  open  por- 
celain evaporating  basin,  will  heat  from  60°  to  212°  F., — 
1  quart  in  5  minutes. 
1  gallon  in  15  " 
2gallonsin30  " 
and  when  the  water  boils  it  is  driven  off"  in  steam  at  the  rate  of 
more  than  a  gallon  of  water  per  hour.  The  method  is  con- 
sequently applicable  to  distillation  on  a  small  scale,  and  to 
numerous  operations  in  pharmacy. — Chem.  News,  London,  Nov. 
2,  1861. 
