60 
ON   TESTING  ARSEN1URETTE D  HYDROGEN  SPOTS. 
protective  power  of  this  preparation  of  sugar  is  considerable,  yet  a  saturated 
saccharine  solution  of  the  protiodide  resists  the  penetration  of  the  atmos- 
pheric oxygen  much  more  effectually.  The  only  objection  to  the  syrupy  con- 
sistence is  a  less  facility  of  dropping,  a  fault  too  trivial  to  weigh  against  the 
increased  protective  power  given  by  the  additional  sugar. — Ed.  American 
Journal  of  Pharmacy.] 
ON  THE  TESTING  OF  THE  METALLIC  SPOTS  DEPOSITED  BY 
BURNING  HYDROGEN  ON  PORCELAIN. 
By  H.  Wackenroder. 
A  new  method  of  distinguishing  arsenical  and  antimonial  spots 
was  sometime  since  proposed  by  Slater.  Wackenroder  has  tried 
this  method,  and  published  the  following  observations  on  the  mode 
of  determining  arsenic  by  separation  from  arseniuretted  hydrogen. 
If  the  hydrogen  gas  produced  by  the  action  of  diluted  pure  or 
ordinary  purified  sulphuric  acid  upon  common  zinc  be  kindled,  and 
the  strong  current  of  gas  directed  against  white  earthenware,  a 
black  spot  of  lead  will  be  produced  by  the  reduction  of  the  lead- 
glazing  of  the  earthenware. 
If  a  very  strong  current  of  hydrogen  gas  be  developed,  and  no 
deposit  of  metal  takes  place  from  its  flame  upon  porcelain,  we  may 
feel  perfectly  sure  of  the  purity  of  the  gas. 
But  if  muriatic  acid  be  employed  instead  of  sulphuric  acid  for 
the  production,  or  if  any  chloride  exists  in  the  fluid  used,  metallic 
spots  may  be  formed  during  the  rapid  evolution  of  the  gas,  which 
however  are  only  spots  of  zinc.  They  are  distinguished  in  this 
manner,  that  on  pouring  over  them  diluted  muriatic  acid,  they  ra- 
pidly disappear,  and  that  they  are  also  readily  removed  by  means  of 
hypochlorite  of  soda. 
To  avoid  error,  it  is  also  necessary  that  no  nitric  acid  or  sulphuret 
be  present  in  the  apparatus  used  in  the  development  of  the  gas, 
which  may  be  best  formed  of  a  two-necked  bottle  with  a  funnel- 
tube  and  a  tube  bent  at  right  angles  and  drawn  to  a  point,  for  the 
passage  of  the  gas.  The  nitrous  acid  formed  in  the  one  case  readily 
decomposes  antimoniuretted  and  arseniuretted  hydrogen  gas,  whilst 
a  sulphuret  readily  causes  the  formation  of  some  sulphuretted  hy- 
drogen gas,  by  which  the  spots  of  arsenic  and  antimony  receive 
more  or  less  of  a  reddish  or  yellowish  color. 
Granulated  zinc  with  dilute  sulphuric  acid  evolves  hydrogen  gas 
