AMOUNT  OF  ARSENIC  IN  PHOSPHORUS  OF  COMMERCE.  507 
part  of  the  solution,  which  adhered  to  the  small  amount  of  crys- 
tals formed.  The  gelatinous  mass  was  redissolved  in  alcohol  and 
set  aside  to  evaporate  spontaneously,  with  the  same  result,  it 
being  found  impossible  to  remove  the  crystals  with  any  degree 
of  nicety  from  the  gelatinous  mass. 
I  then  made  a  solution  of  sulphocarbolate  of  quinine  of  defi- 
nite strength,  a  teaspoonful  of  the  solution  representing  2  grains 
of  the  crystallized  salt,  or  as  near  2  grains  as  I  could  calculate 
from  the  amount  of  substance  used.  The  liquid  was  composed 
of  three  parts  water  and  1  part  alcohol,  and  set  aside  for  pre- 
scription use.  In  about  4  or  5  weeks  I  noticed  small  crystals 
forming,  which  gradually  increased  in  size,  the  large  crystals 
resembling  those  of  perchloride  of  iron.  Under  the  microscope 
they  made  a  beautiful  prismatic  appearance,  but  to  what  system 
of  prisms  they  belonged  I  was  unable  to  determine.  Part  of  the 
crystals  were  taken  out  of  the  bottle  and  examined,  and  found 
to  be  sulphocarbolate  of  quinine. 
In  about  two  months  about  one-third  of  the  salt  had  crystal- 
lized out  of  the  solution.  The  salt  was  freely  soluble  in  water, 
but  slightly  soluble  in  alcohol,  and  not  deliquescent. 
Louisville,  Oct  6,  1870. 
,  ^ 
AMOUNT  OF  ARSENIC  IN  PHOSPHORUS  OF  COMMERCE. 
By  C.  J.  Rademaker,  M.  D. 
Frequently  preparing  dilute  phosphoric  acid  according  to  the 
process  of  the  U.  S.  P.,  I  always  pass  a  current  of  sulphydric  acid 
through  the  solution,  in  order  to  free  it  from  all  substances  pre- 
cipitable  by  that  agent  in  acid  solutions,  and  invariably  obtain  a 
yellowish  precipitate,  which  upon  examination  proves  to  be  sul- 
phide of  arsenic. 
In  order  to  find  the  amount  of  arsenic  present  in  a  given 
quantity  of  phosphorus  the  following  process  was  resorted  to  : 
One  hundred  grammes  of  phosphorus  were  oxidized  with  nitric 
acid,  the  solution  diluted  and  the  arsenic  precipitated  as  a  sul- 
phide (AsSj)  by  means  of  sulphydric  acid,  the  solution  allowed 
to  rest  for  6  days.  The  precipitated  sulphide  of  arsenic  was 
collected  on  a  filter  and  washed,  transferred  to  a  small  evaporat- 
