ON  THE  VALUATION  OF  CHLORIDE  OF  LIME.  347 
amount  of  sulphuretted  hydrogen  gas  to  flow  over  the  salt  while 
it  is  being  dried,  an  apparatus  to  evolve  the  gas  being  kept  at 
hand  during  the  operation.  The  effect  of  adding  the  g.as  is, 
that  the  brown  salt  almost  immediately  becomes  white.  As  soon 
as  this  bleaching,  so  to  speak,  is  effected,  the  stream  of  gas  is 
withdrawn  and  the  drying  continued,  and  only  resumed  if  iodine 
should  be  liberated  a  second  time.  If  the  salt  is  well  prepared 
at  first,  it  seldom  needs  the  second  application.  As  soon  as  the 
salt  is  dry,  it  should,  while  warm,  be  put  into  a  dry  stoppered 
bottle,  as  it  is  deliquescent.  As  long  as  the  salt  is  dry,  it  will 
keep  a  long  time  colorless,  but  if  it  get  damp,  it  is  partially  de- 
composed and  again  gets  brown,  but  its  colorless  condition  may 
again  be  restored  by  a  repetition  of  the  above  treatment. 
It  must  be  admitted  that  an  infinitesimal  amount  of  sulphur 
finds  its  way  in  among  the  salt,  by  the  use  of  the  sulphuretted 
hydrogen  gas  as  a  decolorizer  ;  in  fact,  whatever  quantity  of  that 
gas  is  actually  consumed,  has  its  sulphur  precipitated  into  the 
hydriodate.  To  show,  however,  that  this  is  really  no  drawback 
to  the  use  of  the  gas,  I  may  mention  that  an  exceedingly  small 
amount  of  free  iodine  is  enough  to  communicate  a  considerable 
depth  of  color  to  a  comparatively  large  amount  of  the  hydrio- 
date. Now,  it  is  to  yield  hydrogen  to  this  iodine  that  the 
sulphuretted  hydrogen  gas  is  employed.  The  greater  part  of  the 
"^gas  is,  however,  dissipated  as  such,  and  the  quantity  of  sulphur, 
therefore,  is  necessarily  small  in  quantity  ;  in  fact,  it  is  so  mi- 
nute, that  I  have  not  been  able  to  detect  its  presence  in  the 
samples  I  have  prepared  by  this  process,  although  I  employed 
our  most  delicate  tests  for  sulphur.  I  beg,  therefore,  to 
recommend  the  above  process  for  adoption  in  the  preparation  of 
hydriodate  of  ammonia,  a  salt  which  most  will  agree  is  far  from 
being  easily  obtained  in  a  colorless  condition. — London  Pharm. 
Journ.  May,  1861. 
ON  THE  VALUATION  OF  CHLORIDE  OF  LIME. 
Some  years  back  Mr.  Mercer  suggested  a  process  for  assaying 
chloride  of  lime,  depending  on  the  use  of  ferrocyanide  of  pot- 
assium. This  process  will  be  found  described  in  Parnell's  work 
on  Analysis.  It  consisted  in  adding  so  much  of  the  chloride 
of  lime  to  a  known  weight  of  the  ferrocyanide  as  exactly  to 
