466 
Chemical  Notes, 
'  Am.  Jour.  Pharm. 
i      Sept.,  1880. 
cient  to  boil  the  s.:bstance  in  an  acetic  solution  with  1  ad  peroxide 
until  the  liquid,  on  settling,  is  colorless  and  has  not  the  slightest  odor 
of  bromine  or  iodine.     The  bromine  and  a  part  of  the  iodine  escape  as 
such;  the  remainder  of  the  iodine  remains  as  lead  iodate  along  with 
the  excess  of  the  lead  peroxide.     On  filtering  and  washing  the  precipi- 
tate all  the  chlorine  is  found  in  the  filtrate  free  from  bromine  and 
iodine.     In  this  manner  the  chlorine  may  be  determined  quantitatively. 
If  the  quantity  of  chlorine  accompanying  the  iodine  is  considerable 
manganese  peroxide  is  preferable  to  lead  peroxide,  as  otherwise  the 
liquid  must  be  largely  diluted  with  water  to  prevent  lead  chloride  from 
depositing.     In  determining  large  quantities  of  chlorine  in  presence  of 
bromine  it  is  well  to  add  along  with  the  lead  peroxide  some  potassium 
sulphate,  so  that  all  the  chlorine  may  be  found  in  the  filtrate  combined 
with  potassium.    In  order  to  expel  the  liberated  bromme  and  iodine 
more  rapidly  a  moderate  current  of  air  may  be  passed  through  the 
solution  on  the  water-bath. — Chem.  News^  June  18,  1880. 
Onjhe  Behavior  of  Sulphuretted  Hydrogen  with  the  Salts  of  the  Heavy 
Metals. — H.  DelfFs  calls  attention  to  the  different  precipitability  of  the 
metallic  salts  in  presence  of  a  strong  mineral  acid  on  the  one  hand  and 
of  acetic  acid  on  the  other.  Just  as  the  limit  between  precipitable  and 
non-precipitable  salts  is  altered  by  the  use  of  acetic  acid  instead  of 
hydrochloric  acid  it  is  further  modified  if  formates  are  treated  with  sul- 
phuretted hydrogen.  In  that  case  the  salt  of  zinc  is  precipitated,  but 
the  compounds  of  cobalt,  nickel,  iron  and  manganese  are  not  affected. 
Manganese  cannot  be  precipitated  by  sulphuretted  hydrogen  from  pro- 
pionic, butyric  and  valerianic  solutions.  In  precipitations  by  this  last 
reagent  several  metals  are  never  simultaneously  converted  into  the  cor- 
responding sulphides,  but  the  precipitation  ensues  in  such  manner  that 
one  metal  is  first  completely  separated  before  the  removal  of  another 
begins.  Upon  this  fact  is  founded  a  very  convenient  method  for 
obtaining  cobalt  and  nickel  in  a  state  of  purity.  As  sulphuretted 
hydrogen  first  completely  precipitates  cobalt  acetate,  and  then  acts  upon 
nickel  acetate,  a  solution  of  the  two  nitrates  is  mixed  with  sodium 
acetate  in  quantity  insufficiant  for  complete  double  decomposition,  and 
sulphuretted  hydrogen  is  introduced  so  that,  according  to  the  respective 
proportions  of  the  two  metals,  either  nickel  free  from  cobalt  is  obtained 
in  solution,  or  cobalt  free  from  nickel  as  a  precipitate.  The  required 
quantity  of  sodium  acetate  may  be  calculated  from  the  relative  quan- 
tities of  the  two  metals  which  are  mostly  known. — Ibid.^  p.  279. 
