342 
NOTES  ON  PRESCRIBING. 
R  Potassii  iodicli  ^i. 
Potassse  bicarbonatis  3iss. 
Ferri  et  quiniaa  citratis  £iv. 
Tinct.  Valerianae  ammoniatae  Ij. 
Aquae  ad  §iv. 
Misce.  Sumat  cochleare  medium  ex  aqua  ter  die. 
In  preparing  this  medicine,  the  iodide  and  bicarbonate  were 
dissolved  in  a  portion  of  the  water,  to  which  the  tincture  was 
then  added.  The  citrate  was  dissolved  in  the  remainder  of  the 
water  and  the  two  solutions  were  mixed.  The  result,  as  might 
be  expected,  was  that  a  frothy  white  precipitate  of  quinia  was 
instantly  formed,  which  in  a  few  minutes  collected  into  a  cohe- 
rent mass,  sufficiently  hard  and  tough  to  be  rolled  into  pills. 
It  may  be  observed  that  in  compounds  such  as  this,  the  quinia 
is  not  subject  to  the  remarkable  influence  which  citric  or  tartaric 
acid  exerts  on  peroxide  of  iron, — that  of  allowing  it  to  be  com- 
bined with  an  alkaline  bicarbonate  or  with  ammonia — but  that  it 
is  more  or  less  separated  when  such  alkalies  are  mixed  with  it,  a 
fact  very  often  overlooked. 
A  third  instance  of  extremely  unsuitable  combination  occurs 
to  me,  which  from  its  frequency  a  few  years  ago  was  impressed 
on  my  memory,  although  I  have  no  copy  of  a  prescription  in 
which  it  was  ordered.  It  was  the  prescribing  of  glacial  phos- 
phoric acid  in  pills,  and  that  in  combination  with  valerianate  of 
zinc ! 
Formula?  that  give  rise  to  unexpected  combinations. 
A  very  interesting  fact  bearing  on  this  point  has  been  stated 
in  a  recent  number  of  the  Journal  de  Pharmacie  et  de  Chimie.* 
M.  Melsens  has  proved  by  experiment  that  pure  iodide  of  potas- 
sium may  be  administered  to  dogs  in  considerable  doses  without 
occasioning  any  ill  effects  ;  and  that  chlorate  of  potash  in  some- 
what strong  doses  is  also  tolerated  when  administered  continu- 
ously for  at  least  a  month.  Treated  with  iodate  of  potash,  how- 
ever, dogs  die  rapidly.  If  iodide  of  potassium  and  chlorate  of 
potash  in  equivalent  proportions  are  given  to  dogs,  such  mixture 
speedily  proves  fatal ; — and  yet,  as  is  well  known,  these  salts  do 
not  under  ordinary  circumstances  decompose  one  another.  These 
*  November,  1866,  page  338. 
