492  Petrolatum  in  the  Officinal  Ointments.  {^'"ocT^'iSr"* 
latum,  gradually  added,  until  they  are  thoroughly  mixed.  Preferred 
for  therapeutical  reasons. 
Unguentum  Hydrargyri  Nitratis. — Citrine  Ointment. — The 
practice  which  has  been  indulged  in  to  some  extent  of  making  citrine 
ointment  from  petrolatum  is  one  which  should  be  condemned.  The 
well-recognized  therapeutic  effects  caused  by  the  use  of  this  ointment 
are  probably  due  not  only  to  the  presence  of  the  acid  nitrate  of  mercury, 
but  to  the  elai'din  produced  by  the  action  of  nitric  acid  upon  olein. 
Now  it  has  been  shown  by  Schorlemmer  that  hot  nitric  acid  attacks 
octane,  one  of  the  higher  members  of  the  paraffin  group,  and  that  suc- 
cinic acid  is  one  of  the  products,  but  it  is  yet  to  be  proved  that  the 
resulting  compounds,  if  any,  produced  by  reacting  upon  petrolatum 
with  nitric  acid,  under  the  circumstances  detailed  by  the  officinal  pro- 
cess are  valuable.  Indeed,  it  is  very  probable  that  the  chemical 
changes  are  slight,  and  it  is  very  fair  to  assume,  that  totally  different 
products  must  result  when  a  mixture  of  paraffins  is  treated  with  nitric 
acid  than  when  the  olein  in  an  animal  oil  is  so  treated. 
Practical  results  seem  to  verify  this  view,  for  the  attempts  to  pro- 
duce ointment  of  nitrate  of  mercury  from  petrolatum,  which  have  been 
made  by  various  investigators  from  time  to  time,  have  proved  failures, 
a  spongy  yellowish  mass,  filled  with  bubbles  of  gases  resulting  from 
decomposition,  and  ultimately  turning  brown,  is  the  result.  The  pres- 
ent officinal  process,  if  strictly  adhered  to,  gives  an  excellent  product, 
and,  for  the  reasons  above  given,  the  writer  recommends  it  in  prefer- 
ence to  all  others. 
Unguentum  Hydrargyri  Oxidi  Flavi. — Ointment  of  Yellow 
Oxide  of  Ifercury. — Yellow  oxide  of  mercury,  in  very  fine  powder,  ten 
parts  ;  ointment  (made  from  petrolatum  ;  see  unguentum)  ninety  parts. 
Rub  the  oxide  of  mercury  with  the  ointment,  gradually  added  until 
they  are  thoroughly  mixed.  Preferred  to  the  officinal  from  therapeu- 
tical reasons. 
Unguentum  Hydrargyri  Oxidi  Rubri. — Ointment  of  Red 
Oxide  of  Mercury. — Red  oxide  of  mercury,  in  very  fine  powder,  ten 
parts ;  ointment  (made  from  petrolatum  ;  see  unguentum),  ninety  parts. 
Rub  the  oxide  of  mercury  with  a  small  quantity  of  the  ointment  until 
a  perfectly  smooth  mixture  is  obtained ;  then  gradually  add  the  re- 
mainder of  the  ointment,  and  mix  thoroughly.  More  permanent  than 
the  officinal,  and  preferable  therapeutically. 
Unguentum  Iodi. — Iodine  Ointment. — Iodine,  four  parts;  iodide 
