64  Wash-Blue  and  its  Analysis.         { Am^,1^7afB 
On  passing  carbonic  acid  gas  through  the  solution,  the  acid  unites 
with  the  soda,  and  the  alumina  is  precipitated,  leaving  carbonate  of 
sodium  in  solution.  Aluminate  of  sodium  is  now  manufactured  to  a 
considerable  extent,  and  is  used  in  the  place  of  soda  and  potash  lye  in 
the  making  of  soaps,  and  is  considered  superior  to  either  as  a  detergent. 
Fluoride  of  calcium,  the  by-product  in  the  manufacture  of  soda  from 
cryolite,  is  used  in  large  quantities  as  a  flux  in  the  reduction  of  iron, 
gold  and  other  metals.  Taking  everything  into  consideration,  the  pro- 
cess of  making  soda  from  cryolite  has  many  advantages  over  the  old 
process  of  making  it  from  barilla,  the  ash  of  marine  plants  of  southern 
Europe,  or  from  kelp,  the  ash  of  sea  weeds.  It  generally  takes  about 
24  tons  of  sea  weed  to  make  one  ton  of  barilla  or  kelp.  The  per- 
centage of  soda  in  barilla  is  25  per  cent.,  and  in  kelp  not  over  7  per 
cent.  They  are  used  only  in  the  manufacture  of  iodine  now.  About 
the  year  1804,  Leblanc  discovered  and  introduced  the  process  of 
making  soda  from  sea  salt  or  chloride  of  sodium.  It  is  rather  com- 
plicated, and  consists  of  heating  the  salt  with  sulphuric  acid  to  form 
sulphate  of  sodium,  roasting  this  with  limestone  to  convert  it  into  an 
impure  carbonate,  which  is  afterward  washed  and  purified.  The 
extensive  soda  manufactories  of  England  all  make  it  from  salt  by  this  or 
similar  processes,  producing  bicarbonate  often  containing  more  impuri- 
ties and  a  smaller  percentage  of  carbonic  acid  than  that  produced  in, 
in  this  country  from  cryolite. 
WASH-BLUE  AND  ITS  ANALYSIS. 
By  H.  G.  Debrunner. 
The  different  pigments  sold  as  "  wash-blue  "  chiefly  consist  of  Prus- 
sian blue,  or  ferric  ferro-cyanide,  (FeCy6)3Fe4-f-i8H20  ;  some  of  them, 
however,  are  prepared  by  immersing  starch  in  cold  solutions  of  indigo  » 
or  anilin  blue,  by  which  process  the  pigment  is  absorbed.  The  latter 
kind  is  not  very  often  met  with  ;  indeed,  I  think  there  is  hardly  any  in 
our  present  market.  The  former  kind  of  blue,  however,  on  which  I 
made  a  series  of  experiments,  is  found  in  almost  every  house,  under 
varying  names,  often  as  a  dry  powder,  put  up  in  "  patent  boxes,"  some- 
times, also,  in  solution. 
Soluble  Berlin  blue,  as  the  term  is  used*  in  science,  is  not  found  in 
the  market.    I  am  referring  to  the  blue  precipitate  formed  on  the  addi- 
