190       Recent  Literature  Relating  to  Pharmacy.  {AmAp0rur;i9oiarm' 
into  a  test-tube  with  two  parts  of  the  suspected  oil.  The  mixture 
is  shaken  vigorously  two  or  three  minutes,  heated  to  boiling,  agi- 
tated in  cork  tube  and  then  let  stand.  If  the  slightest  trace  of  oil 
of  sesame  be  present,  the  liquid  assumes  a  beautiful  rose  color,  pass- 
ing rapidly  to  cherry  red.  The  delicacy  of  the  reaction  is  shown 
by  the  fact  that  the  presence  of  1  per  cent,  of  oil  of  sesame  brings 
the  coloration  within  a  few  minutes,  while  10  per  cent,  caused 
instant  change. —  (Tambon,  J.  Ph.  et  Ch.,  1901,  57.) 
H.  V.  A. 
SEPARATION  OF  PLATINUM  METALS. 
The  platinum  ores  are  roasted,  reduced  with  hydrogen,  washed 
with  water,  then  with  dilute  hydrochloric  acid.  This  removes  alka- 
line salts  and  also  iron  and  zinc.  The  metallic  residue  treated  with 
twice  its  weight  of  sodium  chloride,  the  mixture  warmed  in  a  current 
of  dry  chlorine  at  red  heat.  The  volatile  products  of  this  reaction 
being  condensed  by  appropriate  apparatus,  while  the  residue,  which 
has  been  converted  into  soluble  chlorides  of  the  platinum  group,  is 
dissolved  in  water,  thus  freeing  them  from  the  chlorides  of  silver  and 
lead  respectively.  To  the  solution  of  platinum  metals,  sodium  car- 
bonate and  sodium  nitrate  are  added,  precipitating  all  remaining 
traces  of  metals  foreign  to  the  platinum  group,  leaving  a  solution  of 
the  double  nitrites  of  sodium  and  ruthenium,  platinum,  palladium, 
iridium  and  rhodium  respectively,  while  the  osmium  goes  into  solu- 
tion as  a  sodium  chloro-osmite.  This  solution  is  treated  with  caustic 
soda,  then  with  a  current  of  chlorine  and  distilled,  when  the  osmium 
and  ruthenium  pass  over  as  volatile  peroxides  (Os04  and  Ru04) 
which  are  separated  by  usual  methods.  The  residue  in  the  retort  is 
treated  with  hydrochloric  acid  and  boiled  ;  sodium  nitrite  is  added 
and  then  ammonium  chloride,  when  the  iridium  and  rhodium  are 
precipitated  as  double  nitrites  with  ammonium,  which  are  insoluble 
in  the  presence  of  sal-ammoniac.  The  separation  of  the  iridium 
from  the  rhodium  is  accomplished  through  the  differing  solubilities 
of  the  chloro-sodium  compounds.  The  original  liquid  now  contains 
platinum  and  palladium,  and  the  former  is  separated  from  the  latter 
by  the  formation  of  a  chloroplatinate  of  ammonium,  which  crystal- 
lizes, leaving  palladium  in  the  mother  liquor,  which  is  removed  by 
precipitation  with  cyanide  of  mercury. — (Leidie,  y.  Ph.  et  Ch.y  1901, 
18.)  H.  V.  A. 
