38  Precipitation  of  the  Alums  by  Sodic  Carbonate.  {^'^'j^Z'-issi!'^' 
of  asbestos  is  rubbed  pretty  roughly  over  the  sieve  cloth.  This  breaks 
it  up  in  such  a  way  that  the  smaller  fragments  pass  through  the 
meshes,  and  are  deposited  on  the  paper  underneath.  After  awhile  the 
portion  which  remains  on  the  sieve  cloth  is  collected  in  one  bundle, 
and  rubbed  again  in  the  same  manner,  and  the  operation  is  repeated 
until  a  sufficient  quantity  has  gone  through.  In  a  few  minutes  enough 
of  the  material  is  obtained  to  last  for  months. 
As  to  the  coarseness  of  mesh  to  use,  I  may  say  that  I  have  used 
No.  10  sieve  (ten  openings  to  the  inch)  with  satisfactory  results.  The 
sieve  is  best  placed  bottom  up,  so  as  to  leave  plenty  of  room  under  the  cloth.. 
The  next  operation  is  to  free  the  sifted  material  from  dust  and  from 
the  finest  particles.  This  is  easily  accomplished  by  placing  the  asbes- 
tos, as  obtained  above,  over  another  sieve  of  finer  mesh  (about  No.  25 
or  No,  30),  and  stirring  it  while  water  is  poured  over  the  sieve.  The 
first  water  which  passes  through  is  quite  milky,  but  it  gradually 
becomes  clearer  as  the  washing  is  continued.  The  washed  asbestos  i& 
then  put  in  a  beaker  glass,  and  boiled  for  about  half  an  hour  with 
strong  hydrochloric  acid  (about  1  part  of  fuming  HCl  to  4  parts  of 
water). 
The  pulp,  after  this  treatment,  is  poured  over  a  perforated  platinum 
plate,  placed  in  a  funnel,^  and  washed  with  distilled  water  until  no 
acidity  is  shown  by  litmus  paper.  The  pulp  is  then  taken  out  of  the 
funnel  and  strongly  heated  in  a  platinum  dish.  After  letting  it  cool 
sufficiently  it  may  be  placed  in  a  wide-mouth  bottle  for  future  use. — 
Jour.  Amer.  Chcm.  Soc,  Nov.,  1882. 
On  the  Precipitation  of  the  Alums  by  Sodic  Carbonate^ 
By  Edmund  J.  Wills,  D.Sc,  F.K.S.,  and  K.  L.  Barr.— By  a  series  of 
experiments  the  authors  find  that  the  precipitation  of  an  alum  by  sodic 
carbonate  takes  place  in  three  stages.  First,  much  carbonate  is  added 
without  any  precipitation  taking  place ;  secondly,  there  is  a  precipita- 
tion according  to  a  continuous  law  until  about  half  the  alum  is  thrown 
down ;  and  thirdly,  the  precipitation  proceeds  according  to  the  previous 
law,  but  with  altered  constants. — Jour.  Amer.  Chem.  Soe.,  Nov.,  1882» 
perforated  platinum  disc,  having  a  stout  platinum  wire  soldered  with 
gold  in  the  centre  of  the  disc,  can  be  used  in  an  ordinary  conical  funnel. 
The  wire  finds  its  place  in  the  stem  of  the  funnel,  and  keeps  the  perforated 
plate  in  position.  (See  "  Chemical  News,"  xlvi,  p.  8).  A  Gooch  crucible 
of  sufficient  size  may  also  be  used  for  the  ^ame  purpose. 
