ON  THE  PRESERVATION  OF  DRUGS  AGAINST  INSECTS.  309 
Mr.  Parrish  is  likewise  of  the  opinion  that  the  dilute  acetic  acid 
of  the  Pharmacopoeia  is  to  be  of  4.5  per  cent,  strength.  By  a 
mixture  of  one  part  of  strong  acid  to  seven  parts  of  water  it 
may  be  obtained,  if  the  strength  of  the  officinal  acetic  acid  is 
increased  to  35  per  cent.,  when  its  specific  gravity  will  be  1.046  ; 
100  grs.  of  this  acid  are  saturated  by  35x100-2— 58.45  grs.  bicar- 
bonate of  potassa.  One  fluidounce  of  this  weighs  455.6944  x 
1.045=476.2  grs.  which  contain  11^=166.67  grs.  of  mono- 
hydrated  acid ;  this  divided  among  8  fluidounces  leaves  for  each 
20.83  grs.,  which  are  saturated  by  17.36  grs.  of  carbonate  of 
lime,  and  34.78  grs.  of  bicarbonate  of  potassa.  By  calculation 
the  percentage  of  this  acid  is  found  35**^6— 4.55,  and  the  speci- 
fic gravity  ^=1.0058 ;  all  these  figures  very  closely  agree  with 
those  calculated  above. 
It  might  therefore  appear  more  advisable  to  order  an  acetic 
acid  of  the  specific  gravity  1.046 ;  the  direction  for  the  dilute 
acid  will  then  be : 
Take  of  acetic  acid,  one  pint ;  distilled  water  seven  pints. 
Mix  them. 
Diluted  acetic  acid  has  the  specific  gravity  1.006,  and  100 
grains  of  it  saturate  7.6  grains  of  crystallized  bi- 
carbonate of  potassa. 
Philadelphia,  May,  1858. 
ON  THE  PRESERVATION  OF  DRUGS  AGAINST  INSECTS. 
By  John  M.  Maisch. 
A  number  of  drugs  are  subject  to  attacks  by  mites,  bugs  and 
other  insects,  to  avert  which,  different  remedies  have  been  pro- 
posed. Besides  the  requisite  effectualness,  it  is  necessary  that 
such  remedies  are  not  injurious  in  any  way  to  the  articles  to  be 
preserved,  and  that  they  are  devoid  of  smell,  or  so  volatile  as  not 
to  leave  any  odor  behind,  after  a  reasonable  exposure  to  the  air. 
To  meet  with  an  article  possessing  these  requisites,  is  often  not 
an  easy  matter,  particularly  if  the  drug  to  be  protected  is  in 
powder  or  has  a  delicate  odor.  Camphor  may  answer  the  pur- 
pose in  many  instances  ;  but  the  objection  in  most  cases  will  be 
its  not  being  readily  volatilizable  on  exposure  to  the  air,  owing 
