174 
ON  ALLOYS  OF  IRON  AND  ALUMINIUM. 
for  a  period  longer  or  shorter,  according  to  the  intensity  of  the 
light,  and  a  faint  impression  on  the  bitumen  is  thus  obtained. 
3.  The  stone  is  now  placed  in  a  bath  of  sulphuric  ether,  which 
almost  instantaneously  dissolves  the  bitumen,  which  has  not  been 
acted  upon  by  light,  leaving  a  delicate  picture  on  the  stone, 
composed  of  bitumen  on  which  the  light  has  fallen.  4.  The  stone 
after  being  carefully  washed,  may  be  at  once  placed  in  the  hands 
of  the  lithographer,  who  is  to  treat  it  in  the  ordinary  manner 
with  gum  and  acid,  after  which,  proofs  may  be  thrown  off  by 
the  usual  process.  Prof.  Ramsey  then  proceeded  to  state  that 
the  above  process,  modified,  had  been  employed  with  success  to 
etch  plates  of  steel  or  copper,  without  the  use  of  the  burin  :  1.  The 
metal  plate  is  prepared  with  a  coating  of  bitumen,  precisely  in 
the  manner  noticed  above.  2.  A  positive  picture  on  glass  or 
paper  is  then  applied  to  the  bitumen,  and  an  impression  is  ob- 
tained by  exposure  to  light.  3.  The  plate  is  placed  in  a  bath  of 
ether,  and  the  bitumen  not  acted  upon  by  light  is  dissolved  out. 
A  beautiful  negative  remains  on  the  plate.  4.  The  plate  is  now 
to  be  plunged  into  a  galvano.plastic  bath,  and  gilded.  The  gold 
adheres  to  the  bare  metal  but  refuses  to  attach  itself  to  the  bitu- 
men. 5,  The  bitumen  is  now  removed  entirely  by  the  action  of 
spirits  and  gentle  heat.  The  lines  of  the  negative  picture  are 
now  represented  in  bare  steel  or  copper,  the  rest  of  the  plate 
being  covered  by  a  coating  of  gold.  6.  Nitric  acid  is  now  ap- 
plied as  in  the  common  etching  process.  The  acid  attacks  the 
lines  of  the  picture  formed  by  the  bare  metal,  but  will  not  bite 
into  the  gilded  surface.  A  perfect  etching  is  thus  obtained. — 
Pharm.  Journ.,  Nov.,  1855. 
ON  ALLOYS  OF  IRON  AND  ALUMINIUM. 
By  Professor  Calvert. 
Messrs.  Calvert  and  Johnson,  of  Manchester,  have  succeededjin 
preparing  the  following  alloys  of  iron  and  potassium  :  1st  alloy  : 
four  equivalents  of  iron,  1  ditto  of  potassium.  2d  alloy  :  6  equiva- 
lents of  iron,  1  ditto  of  potassium.  These  alloys  were  prepared 
with  a  view  of  solving  one  of  the  great  chemical  and  commercial 
questions  of  the  day — namely,  that  of  rendering  iron  less  oxidable 
when  exposed  to  a  damp  atmosphere  ;  as  these  gentlemen  believe 
