Am"ju°iy?woh6arm'}      The  U.S.P.  Inorganic  Chemicals.  309 
to  brownish  black  coloration  due  to  the  instantaneous  decomposition 
of  the  compoundSb(HgCl)3  into  SbCl3and  Hg3  which  upon  moistening 
with  water  react  with  the  production  of  white  HgCl  and  SbOCl. 
The  spot  produced  by  both  gases  is  brown,  and  if  the  paper  con- 
taining this  is  cut  out  and  immersed  in  a  watch  glass  containing  80 
per  cent,  alcohol,  the  antimony  spot  disappears,  while  the  distinc- 
tive bright  yellow  arsenic  spot  makes  its  appearance  (Lohman,  Pharm, 
Ztg.y  1892,  36).  Prolonged  action  of  hydrogen  gas  results  in  the 
production  of  calomel.  This  test  may  be  carried  out  with  full  exposure 
to  daylight.  Any  sulfates  or  sulfites  which  might  be  present  and 
reduced  to  hydrogen  sulfid,  may  be  recognized  by  the  blackening 
of  the  lead  acetate  gauze.  The  only  substance  which  may  react 
similar  to  arsine,  is  phosphine  (PH3),  produced  through  the  presence 
of  hypophosphorous  acid  ;  this  is  provided  against  by  the  preliminary 
oxidation  of  the  chemical  by  nitric  acid.  It  will  also  be  noted  (U.  S. 
P.,  p.  322)  that  #// chemicals  are  first  subjected  to  the  action  o;  a  reduc- 
ing agent  before  introducing  into  the  test-apparatus.  This  is  due 
to  the  fact  that  the  greater  part  of  the  arsenic  present  in  chemicals 
is  in  the  "  ic  "  state,  and  that  the  moderate  quantities  of  zinc  and 
acid  employed  in  the  test  are  insufficient  to  secure  complete  reduc- 
tion to  "  ous"  arsenic.  Tests  made  by  Bird  (Ckem.  and  Druggist, 
1900,  1073),  corroborated  by  the  writer,  have  shown  that  when  0-05 
milligramme  of  sodium  arsenate  was  tested  beside  arsenous  acid  con- 
taining the  same  amount  of  arsenic,  the  stain  from  the  former,  in  1 5 
minutes,  was  only  about  one-fourth  of  the  intensity  of  that  from  the 
latter.  Among  the  various  reducing  agents  employed,  sulfurous 
acid1  was  found  to  be  the  least  objectionable  and  most  satisfactory. 
The  quantity  directed,  is  completely  and  readily  removed  by  15 
minutes  heating  upon  the  water-bath. 
The  quantity  of  zinc  and  hydrochloric  acid  (8  per  cent.)  employed 
is  sufficient  to  secure  a  steady  evolution  of  hydrogen  for  at  least 
half  an  hour,  which  will  remove  all  arsenic  that  may  be  present  in 
the  solution  being  tested.    Pure  zinc,  as  is  well  known,  reacts  very 
1  Hydriodic  acid  answers  readily  with  sodium  phosphate,  0.5  gramme  of  the 
salt  is  placed  in  the  test-flask  and  20  c.c.  of  8  per  cent,  hydrochloric  acid  and 
1  c.c.  of  normal  potassium  iodid  solution  added.  The  mixture  is  heated  in  a 
boiling  water-bath  for  five  minutes,  then  quickly  cooled  to  room  temperature, 
the  zinc  added,  etc.,  as  usual.  Five  minutes  heating  is  sufficient  to  effect  the 
reduction. 
