570  ON  THE  EXAMINATION  OF  INDIGO. 
ANALYSES  OF  VARIOUS  KINDS  OF  PORCELAIN. 
Br  Joseph  Muller. 
The  porcelain  used  for  these  analytical  investigations  was 
freed  from  its  glazing,  which  with  thicker  pieces  was  easily  ef- 
fected by  wrapping  them  in  paper,  and  striking  them  with  a 
hammer  ;  for  the  thinner  pieces  the  use  of  the  knife,  chisel  and 
file  was  found  necessary.  On  powdering  it  in  an  iron  mortar, 
much  iron  was  rubbed  off,  which  made  it  requisite  to  digest  the 
powder  with  diluted  muriatic  acid;  after  washing,  it  was  tritu- 
rated to  a  very  fine  powder  in  an  agate  mortar,  and  ignited.  A 
part  of  the  powder  thus  treated  was  fused  with  carbonate  of  lime 
and  chloride  of  ammonium  for  the  determination  of  the  alkalies ; 
for  the  other  ingredients,  another  portion  was  treated  with 
carbonate  of  soda  and  potassa. 
I.  is  porcelain  from  Meissen,  II.  from  Elgersburg,  III.  from 
Ballwitz  in  Bohemia,  IV.  gives  the  result  of  Vielguth's  analysis 
of  Nymphenburg,  V.  Wilson's  analysis  of  Berlin  porcelain. 
I.  ir.  nr.  iv.  v. 
Silicic  acid  60-033  72-77  74  798  72-80  71-340 
Sulphuric  acid    -06  -087    — — 
Sesquioxide  of  iron  trace  trace    2-50  1-743 
Alumina  35-435  24-53  21-303  18-40  23-763 
Magnesia  trace  trace  trace  -30  -192 
Lime  -577    -639  3-30  -568 
Soda  1-547  1-61  -584  1-84   
Potassa  2-264  -94  2484  -65  2-001 
99-856    99-91    99-895   99-79  99-607 
Wittsteins  Viert.  Schr.  viii.  352—354.  J.  M.  M. 
ON  THE  EXAMINATION  OF  INDIGO. 
Br  Joseph  Muller,  of  Prague. 
The  chemical  determination  of  the  commercial  value  of  indigo 
is  very  important,  because,  on  account  of  the  high  price,  it  is 
subject  to  various  adulterations  which  are  not  detected,  and  may 
not  be  suspected  by  the  physical  properties,  the  color,  lustre, 
gravity,  shape,  &c.  The  best  chemical  test,  for  the  use  of  em- 
pirics especially,  is  the  method  first  proposed  by  Pugh,  and  im- 
proved by  Berzelius,  which  consists  in  the  reaction  of  protosul- 
