TINCTURA  FERRI  CHLORIDI. 
457 
nuts  (zV),  the  plate  therefore  presses  without  any  obstruction  on 
the  cloth,  and,  in  addition  to  its  own  weight,  pressure  is  exerted 
upon  it  indirectly  by  the  weights  and  levers,  as  above  stated. 
This  plate  is  nearer  the  perpendicular  than  the  back  plate, 
because  the  spread-plaster  (w)  should  be  drawn  through  as  near- 
ly at  right  angles  with  it  as  possible. 
The  cloth  being  placed  on  a  roller  (w),  which  is  suspended  on 
two  rests  {oo),  is  passed  through  the  bottom  of  the  trough,  tak- 
ing with  it  a  layer  of  the  liquefied  plaster  (contained  in  the 
trough)  as  it  is  drawn  off  at  {m). 
By  regulating  the  front  plate  with  the  screws  (//),  skins, 
felt,  or  other  thick  material  can  be  spread  in  the  same  manner 
as  has  been  described. 
The  condition  of  the  plaster,  its  temperature,  and  that  of  the 
plates  suitable  for  spreading,  are  matters  which  require  careful 
attention  to  produce  satisfactory  results. 
The  heating  apparatus  (p)  is  a  Bunsen's  burner  with  two 
branches  {qqq)^  which  perforate  the  cheeks  at  each  end.  Gas  is 
supplied  by  means  of  an  india-rubber  tube.  A  stopcock  regu- 
lates its  admission  through  a  small  tube  into  the  interior  of  the 
larger  tube.  Air  is  admitted  to  mix  with  the  gas  by  holes  near 
the  bottom  of  this,  the  quantity  being  regulated  by  the  usual 
nozzle.  The  mixture  of  gas  and  air  is  burnt  in  a  row  of  jets  in 
each  branch  directed  against  the  plates  (5  and  c) ;  thus  these 
and  the  liquefied  plaster  in  the  trough  are  kept  at  a  nearly  uni- 
form temperature. 
The  burner  can  be  detached  and  fitted  into  the  machine  in- 
verted, so  that,  when  not  in  use,  the  whole  occupies  but  very 
little  space. 
Mr.  J.  H.  Spencer,  Southwark  Bridge  Road,  constructed  the 
apparatus  under  the  direction  and  supervision  of  the  inventor. 
Lond.  Pharm.  Jour.^  July,  1869. 
TINCTURA  FERRI  CHLORIDI. 
By  James  W.  Mill. 
In  view  of  the  near  approach  of  another  revision  of  the 
Pharmacopoeia,  it  is  proper  that  individual  experience  in  the 
preparation  of  its  various  compounds  should  be  recorded. 
