Am'JJu0ly?l^9h7arm•}      Corrosive  Sublimate  in  Calomel.  339 
nation  showed  that  the  calomel  contained  an  appreciable  quantity  of 
this  poisonous  agent.  Other  makes  were  secured  and  all  developed 
a  greater  or  lesser  yellowish  coloration  when  treated  with  lime- 
water.  The  various  available  products  were  then  critically  exam- 
ined according  to  the  U.S. P.  requirements,  with  the  following  results: 
The  color  varied  from  a  white  to  a  decided  cream.  Isolated  broken 
crystals  were  present  in  all  material  examined.  Minute  traces  of 
mercuric  chloride  were  indicated  in  every  instance. 
Since  examining  the  above  samples  the  writer  has  watched  the 
quality  of  this  article  with  much  interest ;  but  thus  far  all  efforts 
have  failed  to  find  a  calomel  absolutely  free  from  corrosive  sublimate 
when  the  U.S.P.  tests  were  rigidly  applied.  In  two  cases,  however, 
both  the  silver  nitrate  and  the  hydrogen  sulphide  failed  to  give 
absolute  evidence  of  the  mercuric  chloride,  but  a  transitional  yellow 
was  developed  with  even  these  when  treated  with  lime-water.  One 
of  these  was  a  beautiful  crystalline  (plates)  product  of  Japanese 
origin,  the  other  an  old  sample  found  in  the  laboratory. 
Several  questions  arise  in  this  connection.  First,  the  yellowish 
coloration,  and  second,  the  relative  solubilities  of  mercurous  chloride, 
silver  chloride  and  mercurous  sulphide. 
It  is  well  known  that  the  color  of  the  various  compounds  of  mer- 
cury is  readily  modified.  In  precipitating  mercuric  mercury  with 
hydrogen  sulphide,  the  resulting  product  frequently  varies  in  color 
from  white  to  black.  The  writer  on  several  occasions  has  repeatedly 
washed  calomel  with  water,  to  remove  the  soluble  mercury  com- 
pounds, but  in  every  instance  a  yellowish  coloration  was  developed 
at  the  point  of  contact,  when  the  washed  calomel  was  treated  with 
lime-water.  This  would  suggest  the  conclusion  that  calomel 
develops  a  transitional  yellowish  coloration  at  the  point  of  contact 
when  treated  with  lime-water. 
The  second  question,  viz.:  the  relative  solubility  of  the  above- 
named  compounds,  is  an  interesting  one.  We  are  informed  by  the 
Pharmacopoeia,  and  other  standard  works,  that  calomel  is  insoluble. 
Silver  chloride  and  mercurous  sulphide  are  generally  considered 
insoluble.  According  to  A.  M.  Comey's  "  Dictionary  of  Chemical 
Solubilities"  calomel  and  silver  chloride  are  nearly  or  almost  insoluble 
in  water,  while  mercurous  sulphide  is  insoluble. 
F.  Kohlrausch1  and  F.  Rose,  calculating  from  the  electrical  con- 
1  1893,  Ztschr.  phys.  Chem.,  12,  241. 
