MERCURY — ITS  OXIDES  AND  ACETATES,  ETC.  269 
mercurous  salt  by  a  dilute  solution  of  chloride  of  sodium,  filter 
closely  ;  render  the  filtrate  alkaline,  by  careful  addition  of  caus- 
tic potash  ;  if  any  precipitate  occurs,  wash  it  by  decantation  in 
a  test-tube ;  treat  it  with  dilute  hydrochloric  acid  ;  evaporate 
the  clear  solution  to  a  few  drops,  and  add  caustic  potash,  which 
will  produce  a  yellow  precipitate  if  any  mercuric  oxide  is  pre- 
sent. In  this  way  I  was  enabled  to  detect  with  certainty  one 
half  of  one  per  cent,  of  the  two  oxides,  when  mixed  with  the 
mass.  Instead  of  washing  the  mass  with  water,  pure  ether  mixed 
with  alcohol,  can  be  employed.  Cold  water,  is,  however,  suffi- 
ciently accurate,  and  allows  the  coloring  matter  to  be  removed 
more  quickly.  Dilute  chlorohydric  acid  can  also  be  used,  if  the 
red  oxide  alone  is  sought  for,  although  a  small  portion  of  calo- 
mel is  formed  from  the  black  oxide  ;  if  it  is  present,  and  dis- 
solved, there  is  no  conversion  of  any  part  of  it  into  red  oxide. 
The  objection  to  its  use  is,  that  it  takes  up  a  much  larger  por- 
tion of  coloring  matter  than  acetic  acid,  thus  diguising  the  effects 
of  delicate  reagents. 
Blue  Mass  examined  under  a  microscope  shows  globules  of 
mercury,  the  largest  of  which  measures  about  the  _1  of  a  mille- 
metre  in  diameter  (=3^5  of  a  line.)  A  specimen  made  ten 
months  which  had  been  kept  from  the  light,  but  with  access  of 
air,  yielded  nothing  to  dilute  acetic  acid. 
Examination  of  Powdered  Blue  Mass. 
1st.  A  specimen  made  two  months  yielded  nothing  to  dilute 
acetic  acid. 
2d.  Specimen  made  eight  months  yielded  nothing  to  acetic 
acid. 
3d.  Specimen  made  two  years,  and  which  had  been  preserved 
in  a  box,  thus  excluding  light,  but  admitting  air,  was  found  to 
contain  mercurous  oxide ;  by  a  comparative  estimate  with  solu- 
tions of  known  strength,  the  amount  of  oxide  present  appeared 
to  be  from  half  to  one  per  cent.  Repeated  trials  were  made  for 
the  presence  of  red  oxide  of  mercury,  but  none  could  be  detected. 
4th.  Specimen,  a  portion  of  the  preceding,  which  has  been 
kept  in  a  close  show  bottle  in  a  window  exposed  to  light  for 
twelve  months,  and  during  the  winter,  to  direct  sunshine  during 
part  of  the  day. 
