538 
Stability  of  Calomel. 
Am.  Jour.  Pharm. 
Nov.,  1880. 
ON  THE  STABILITY  OF  CALOMEL. 
By  Phil.  Hoglan. 
The  "Druggists'  Circular"  for  August,  1880,  contains  some  of  the 
results  of  M.  Verne's  experiments  on  the  stability  of  calomel,  as 
reported  in  the  Bulletin  de  Therapeutique."  It  is  there  stated  that 
calomel,  mixed  with  sugar,  chloride  of  sodium  or  citric  acid,  undergoes 
no  change,  and  also  that  the  assumed  danger  of  acid  drinks,  taken  when 
using  calomel,  "  is  pure  prejudice,"  since  calomel  in  solution  with  citric 
acid  for  fifteen  days  underwent  no  change.  M.  V^erne  concludes  from 
his  experiments  that  calomel  is  a  much  more  stable  compound  than 
generally  supposed,  and  that  chloride  of  sodium,  at  40°C.,  has  no  action 
whatever  on  calomel.  That  the  subject  of  this  article  is  a  much  vexed 
question  the  reader  will  readily  see  by  referring  to  the  U.  S  Dispen- 
satory, 14th  ed.,  pp.  1247 — ^5  where  experiments  are  quoted  to  prove 
both  the  stability  and  the  unstability  of  calomel. 
The  following  experiments  were  conducted  for  the  purpose  of  ascer- 
taining the  correctness  of  M.  Verne's  conclusions,  and  also  with  a  view 
to  discover  the  cause  of  the  discrepancies  among  different  experimen- 
talists on  this  important  question  : 
1.  Calomel  was  added  to  a  solution  of  chloride  of  sodium  and  allowed 
to  stand  ten  days  with  frequent  agitation,  after  which  the  filtered  liquid 
gave  no  evidence  of  the  presence  of  corrosive  sublimate  by  the  stannous 
chloride  test. 
2.  Calomel  and  chloride  of  ammonium,  treated  in  the  same  manner, 
gave  no  evidence  of  corrosive  sublimate  being  formed. 
3.  Calomel  was  added  to  a  dilute  solution  of  hydrochloric  acid,  and 
after  twenty- four  hours  the  filtered  liquid  gave  a  slight  reaction  with 
stannous  chloride,  indicating  a  trace  of  corrosive  sublimate.  The 
above  experiments  were  conducted  at  a  temperature  of  about  78°F. 
5.  A  mixture  of  calomel  and  a  solution  of  chloride  of  sodium  was 
kept  at  a  temperature  of  gS^F.  for  two  hours,  then  filtered;  the  filtrate 
gave  a  grayish  coloration  with  stannous  chloride,  thus  indicating  the 
presence  of  corrosive  subfmate,  and  showing  that,  contrary  to  M. 
Verne's  conclusions,  chloride  of  sodium  acts  on  calomel  even  below 
40°C. 
6.  Calomel  and  a  solution  of  chloride  of  ammonium,  treated  in  the 
same  manner  as  in  experiment  "  5,"  gave  the  same  reaction. 
7.  Calomel  and  water  were  shaken  together  and  kept  at  a  tempera- 
ture of  qS'^F.  for  three  hours,  when  the  filtered  liquid  gave  a  slight 
