80       ACTION  OF  SUNLIGHT  UPON  IODIDE  OF  POTASSIUM. 
consequence  thereof,  a  report  was  made  to  headquarters,  at  Ber- 
lin, and  a  rigorous  inquiry  and  investigation  set  on  foot  by  order 
of  Dr.  de  Miihler,  as  minister  for  medical  affairs  and  police 
[medizinal  polizei).  The  methods  of  testing  for  arsenic,  when 
mixed  up  with  antimonial  preparations,  were  carefully  consid- 
ered, and  the  following  method  of  testing,  due  to  the  researches 
of  Mine  Inspector  Strohmeyer,  adopted;  2  grms.  of  the  sus- 
pected tartar  emetic  are  reduced  to  a  fine  powder  and  dissolved 
in  4  grms.  of  pure  hydrochloric  acid  (sp.  gr.,  1*124).  The  glass 
vessel  wherein  this  solution  is  made  ought  to  be  narrow,  and 
capable  of  being  well  closed,  and  of  sufficient  size  to  contain  an 
additional  quantity  of  at  least  30  grms.  more  of  hydrochloric 
acid.  A  quantity  of  pure  hydrochloric  acid  should  be  thoroughly 
saturated  with  sulphuretted  hydrogen  gas,  and  of  this  acid  a 
quantity  of  at  least  30  grms.  is  added  to  the  solution  of  the 
tartar  emetic.  The  glass  vessel  containing  the  solution  is  well 
corked,  and,  after  having  been  shaken  up,  set  aside;  the  tur- 
bidity which  at  first  appears  soon  subsides  (if  it  does  not  do  so, 
it  is  due  to  the  too  great  saturation  of  the  HCl  with  HS,  and 
should  be  remedied  by  the  addition  of  some  pure  HCl).  If  no 
arsenic  is  present  at  all,  the  liquid  remains  perfectly  colorless ; 
but  the  slightest  trace  of  arsenic  gives  rise  to  a  yellow  colora- 
tion, and  very  soon  after  to  a  perfectly  perceptible  pure  yellow 
•  precipitate  of  sulphuret  of  arsenic. — Chemical  News,  Dec.  3, 
1869. 
ACTION  OF  DIRECT  SUNLIGHT  UPON  IODIDE  OF  POTAS- 
SIUM. 
By  M.  Loew. 
A  solution  of  iodide  of  potassium  is,  even  when  kept  in  well- 
closed  bottles,  slowly  decomposed  by  the  action  of  daylight,  and 
assumes  a  somewhat  yellowish  tinge,  due  to  free  iodine.  The 
author  filled  a  number  of  glass  tubes  for  about  from  one-half  to 
three-fourths  of  their  capacity,  with  a  solution  of  iodide  of 
potassium,  and,  after  having  sealed  these  tubes,  exposed  them  to 
direct  sunlight.  Another  set  of  tubes  were  likewise  filled  with 
the  same  solution,  but  all  air  was  expelled,  and  the  tubes  sealed 
