162  Manufacture  of  Vermillion.  {^\^ri\\mT''' 
shows  that  the  demand  for  its  products  is  the  greatest  stimulant  to 
increased  production  and  cheapening  cost.  In  this  is  to  be  seen  a 
decided  step  toward  the  artificial  production  of  morphine,  quinine^ 
etc. — American  Practitioner,  Marchj  1871. 
OBSERVATIONS   ON   I'HE   MANUFACTURE  OF  VERMILLION, 
By  M.  Ai.SBERG,  Ph.  D. 
In  the  process  of  manufacturing  vermillion  bj  Martin's  method 
(agitation  of  quicksilver,  sulphur  and  alkaline  sulphuret),  two  differ- 
ent stages  can  be  easily  distinguished  ;  first,  the  combination  of  mercu- 
ry and  sulpliur  to  the  black  sulphide  ;  and  secondly,  the  conversion 
of  this  amorphous  black  modification  into  the  crystalline  red.  The 
chemical  combination,  as  well  as  the  crystallization,  is  accompanied 
by  the  evolution  of  considerable  heat,  which  may  become  so  great, 
especially  during  the  latter  stage,  and  when  working  in  closed  vessels, 
as  to  give  rise  to  dangerous  explosions. 
The  crystallization,  a  consequence  of  the  solubility  of  the  black 
sulphide  in  the  alkaline  sulphuret,  and  its  gradual  precipitation  in  the 
red  form,  only  takes  place  when  the  mass  is  warm.  If  it  be  kept 
cold  it  requires  a  great  length  of  time,  often  weeks,  and  even  months, 
until  the  crystals  are  formed.  If,  on  the  contrary,  the  crystallization 
has  once  set  in  (this  is  indicated  by  the  black  mass  turning  brown),  it 
is  generally  finished  within  twenty-four  hours.  In  the  case  of  the 
slow  crystallization,  there  are  sometimes  crystals  obtained,  which,  in 
color  and  form,  greatly  resemble  the  native  ore  ;  the  same  crystals  are 
occasionally  formed  when  the  solution  of  alkaline  sulphuret  contain- 
ing sulphide  of  mercury  is  concentrated.  Professor  J.  P.  Cooke,  Jr., 
of  Cambridge,  who  examined  some  crystals  of  that  kind,  says  :  — 
"  They  were  rhombohedra,  approaching  a  cube,  and  have  the  peculiar 
form  of  macling,  which  is  so  characteristic.  They  are,  doubtless,  the 
primitive  rhombohedra  observed  on  the  native  crystals,  R  on  R  92° 
36^  The  faces  are  striated  parallel  to  the  basal  diagonal  of  the 
rhomb  face,  and  the  crystals  are  terminated  by  the  plane  of  a  more 
obtuse  rhombohedron  of  the  same  order." 
The  solubility  of  the  sulphide  of  mercury  in  the  alkaline  sulphurets 
is  considerable,  especially  when  the  fluids  are  concentrated,  and  then 
even  in  the  presence  of  polysulphurets.  This  solution  cannot  be  di- 
luted without  the  sulphide  of  mercury  being  precipitated  in  the  black 
