494 
Laboratory  Notes. 
f  Am.  Jour.  Pharm. 
t     Nov.  1, 1872. 
although  professedly  pure,  and  "equal  to  Price's,"  are  not  always  re- 
liable ;  either  the  gravity  is  low,  or  they  are  not  odorless,  or  perfectly 
free  from  metallic  impurity.  One  specimen,  apparently  pure,  I  found 
to  contain  a  notable  amount  of  some  sulphur  compound  (not  deter- 
mined), probably  arising  from  H2S  having  been  used  to  free  the  gly- 
cerin from  metals.  It  had  a  sp.  gr.  ==  1-250,  without  odor,  free 
from  metallic  impurity,  and  generally  stood  the  usual  tests.  On  warm- 
ing gently  with  dilute  acid,  H2S  was  given  off  in  sufficient  quantity 
readily  to  react  upon  lead  paper,  and  to  discolor  metallic  solutions. 
A  mixture  composed  of  dilute  acid  and  this  glycerin  and  water  be- 
came highly  offensive  within  a  couple  of  hours  at  the  ordinary  tem- 
perature. As  glycerin  and  dilute  acid  frequently  enter  into  the  com- 
position of  mixtures  and  lotions,  the  occurrence  of  sulphur  in  the  for- 
mer is  a  possibility  which  dispensers  should  bear  in  mind.  Its  pres- 
ence can  readily  be  detected  as  above  indicated. 
Bismuth. — The  common  impurities  of  metallic  bismuth  are  arsenic, 
antimony,  copper  and  lead.  I  have  very  rarely  met  with  lead,  but 
my  experience  is  perhaps  somewhat  limited.  The  amount  of  arsenic 
and  antimony  is  generally  small,  and  will  not  require  here  any  espe- 
cial attention,  since  the  greater  portion  (if  not  quite  all),  of  these  two 
metals  is  eliminated  during  the  subsequent  treatment  for  the  removal 
of  copper,  which  latter  is  the  most  difficult  metal  to  get  rid  of. 
In  the  purification  of  commercial  bismuth,  instead  of  following  the 
B.  P.  method  of  fusing  with  nitre,  I  have  adopted  the  process  of  Hugo 
Tamm,*  which  has  proved  in  my  hands  exceedingly  efficient  and  sat- 
isfactory. The  treatment  consists  simply  in  fusing  the  coppery  bis- 
muth with  potassium  sulphocyanide.  Tamm  says,  "  The  sulphocyan- 
ide  which  I  use  is  prepared  by  mixing  eight  parts  of  cyanide  of  potas- 
sium and  three  parts  of  flowers  of  sulphur.  One  part  of  this  mixture 
is  thrown  over  sixteen  parts  of  the  metal  melted  at  a  low  tempera- 
ture." A  bright  red  heat  is  sufficient,  such  as  may  be  readily  ob. 
tained  by  almost  any  Bunsen  burner. 
In  order  to  satisfy  myself  of  the  thorough  elimination  of  the  cop- 
per by  this  process,  a  sample  of  coppery  metal  and  the  resulting  puri- 
fied button  were  carefully  examined  as  follows  : 
3-2585  grains  of  the  impure  bismuth  were  dissolved  in  dilute  nitric 
acid,  ammonium  chloride  added,  and  the  bismuth  precipitated  as  oxy- 
*  Chemical  News,  Yol.  xxv,  p.  100. 
