BRONZE  POWDER. 
357 
sulphuric  or  hydrochloric  acid,  the  color  immediately  disappears, 
owing  to  the  solution  of  the  thin  layer  of  suboxide,  and  the 
proper  color  of  the  alloy  appears.  The  amount  of  oxygen  could 
not  be  estimated  in  any  of  these  bronzes,  but  it  did  not  amount 
to  one-thousandth.  The  bronze  powder  called  white,  contains 
zinc  and  tin.  The  bronzes  3 — 7  were  also  found  to  contain  a 
minute  quantity  of  fat,  which,  on  dissolving  the  powder  in  dilute 
acid,  separated  upon  the  surface  of  the  liquid  in  the  form  of  a 
thin  film. 
The  quantitative  analysis  of  the  alloys  gave  the  following 
results : — 
Copper. 
Zinc. 
Iron. 
Tin. 
Remarks. 
1.  Pale  yellow,  . 
82.33 
16.69 
0.16 
2.  Yellow, .    .  . 
84.50 
15.30 
0.07 
Fine  golden  yellow 
3.  Reddish  yellow 
90.00 
2.60 
0.20 
| 
Brass  yellow,  with 
a  shade  of  red 
The  color  of  clean 
4.  Orange,     .  . 
98.93 
0.73 
0.08 
copper  that  has 
been  heated 
Copper  color, 
5.  Copper  red,  . 
99.90 
trace 
with  a  shade 
[  of  purple 
6.  Violet,  .    .  . 
98.22 
0.50 
0.30 
trace 
Purple  violet 
7.  Green,  .    .  . 
84.32 
15.02 
0.03 
trace 
Bright  bluish-green, 
8.  White,  .    .  . 
2.39 
0.56 
56.46 
\ 
Between  tin  white 
and  lead  grey 
These  results  show  that  bronzes  of  the  most  different  colors 
possess  nearly  the  same  composition.  The  action  of  acid  shows, 
likewise,  that  their  color  is  owing  to  different  degrees  of  oxyda- 
tion.  It  appears  therefore  probable,  that  in  the  preparation  of 
bronze  powders  a  certain  alloy  is  used  for  all,  and  that  the 
colors  are  produced  by  heating  to  different  temperatures.  This 
Hr.  Konig  found  to  be  the  case.  In  his  experiments  with  the 
above-named  powders,  No.  1,  when  heated,  presented  succes- 
sively all  the  prismatic  colors,  and  acquired  a  fine  dark  violet. 
Most  of  the  other  bronzes  presented  the  same  character,  and 
when  the  heat  was  maintained,  lastly  became  black,  from  com- 
plete oxydation. 
Hr.  Konig  is  of  opinion  that  the  fat  in  these  bronze  powders 
originates  from  the  use  of  fat  in  their  preparation,  for  the  pur- 
pose of  ensuring  uniform  temperatures.    Tallow  or  fat  oils 
