i40  Preparation  of  Mercurial  Ointment,  { *^'"'Jar.?i8to.'''"' 
gestion,  not  believing  in  the  second  ;  e.^  I  used  ozonized  lard  for 
triturating,  but  not  for  shaking  with  the  mercury  ;  the  ointment  was 
completed  in  a  much  shorter  period  than  with  pure  lard,  but  a  much 
longer  time  was  required  than  with  old  ointment. 
11.  Overbeck  thinks  that  old  ointment  contains  mercury  in  combi- 
nation, and  thus  explains  the  success  with  it  in  extinguishing.  I  shall 
prove  that  this  is  not  the  case. 
12.  Geissler  recommends  steam-power  as  it  is  used  in  England,  the 
machine  used  consisting  of  a  circular  iron  trough,  constantly  kept  in  a 
rocking  motion,  in  which  two  iron  balls  take  the  place  of  the  pestle. 
A  porcelain  apparatus,  constructed  on  the  same  plan,  is  used  for 
dissolving  indigo  in  sulphuric  acid.  I  believe  that  it  is  far  superior  to 
manual  labor  for  preparing  the  ointment,  although  I  do  not  see  any 
extraordinary  virtues  in  it. 
13.  Prof.  Ludwig's  plan  was  to  precipitate  the  mercury  in  globules, 
invisible  to  the  naked  eye,  from  a  solution  of  nitrate  of  mercury,  by 
conducting  sulphurous  acid  gas  into  it,  and,  after  washing  it,  to  mix  it 
with  the  fatty  matter.  I  did  not  try  this  method,  but  believe  that  it 
would  be  used  more  extensively  if  it  yielded  reliable  results. 
14.  Magnus  triturates  with  almond  oil  and  Peruvian  balsam.  The 
oil  was  tried  by  me  unsuccessfully,  while  the  balsam  seemed  objec- 
tionable to  me,  for  which  reason  I  did  not  test  its  efficacy. 
15.  Another  author  suggests  2  parts  of  lard  and  i  part  of  Japan 
wax,  which  mixture  is  less  adapted  for  extinguishing  the  mercury  than 
iard  alone. 
16.  Adolph  Brejcha  uses  glycerin  ointment,  with  which  I  obtained 
very  unfavorable  results. 
17.  Wallet  suggests  adding  the  mercury  in  small  quantities,  gradu- 
ally, to  the  fat,  and  extinguishing  each  portion  entirely  before  adding 
another.  This  is  a  very  sensible  suggestion,  and  will  always  yield  a 
good  ointment  in  a  comparatively  short  time. 
18.  Another  author  claimed,  four  or  five  years  ago,  that  lard  con- 
taining no  water  is  equally  well  adapted  as  old  ointment.  I  cannot 
corroborate  this  statement,  but  find  that  it  does  not  extinguish  the  mer- 
cury any  quicker  than  lard  containing  water,  although  I  consider  the 
former  far  preferable  for  preparing  any  ointment,  since  the  absence  of 
water  is  the  best  remedy  for  preventing  rancidity. 
19.  Supposing  that  rancid  fat  extinguishes  mercury  more  quickly 
than  not  rancid  fat,  and  attributing  this  apparently  greater  affinity  for 
