The  part  a  b  is  heated  red  hot,
^^S'  382.  when,  if  arsenic  is  present,  it  is

sublimed  in  a  black  metallic  mirror  at  c.  A  small  tube  is
used,  because  in  many  cases  very  minute  portions  are  ope-


What  are  antidotes,  and  why  ?  How  does  sulpbydric  acid  act  as  a  rest
of  arsenic  ?  How  nitrate  of  silver  and  ammonia  ?  How  ammonia-sul-
phate of  copper?  What  is  Reinsch's  test?  What  of  the  reduction  pre-
ferred?     Describe  from  fig.  382.
ARSENIC.
359


rated  on.     In  order  to  prove  the  character  of  this  ring,  the

tube  is  broken  off  at  h,  (fig.  383,)  and  the

flame  of  a  spirit-lamp  applied  cautiously

while  the   tube  is  gently  inclined.     A

current  of  air  passing  over  the  ring  of

metal  converts  it  to  arsenious  acid,  which

lines  the  cooler  parts  of  the  tube  with

small   brilliant    octahedrons    of   a   size

visible  by  a  magnifier.     If  further  proof

were  required,  a  current  of  sulphydric  ^^*

acid  will  convert  the  white  crust   into    yellow  orpiment,

wholly  soluble  in  ammonia,   precipitated  by  chlorohydric

acid,  and  insoluble  in  that  menstruum.
