158  Moisture  in  Air-dry  Drugs.  {^Tdm™* 
cost,  combined  with  the  practicability  of  using  it,  will  recommend  it 
to  the  more  careful  examination  of  druggists  who  deal  extensively  in 
this  preparation. 
ON  THE  AMOUNT  OF  MOISTURE  CONTAINED  IN  AIR-DRY 
DRUGS. 
By  Geo.  W.  Kennedy. 
Read  at  the  Pharmaceutical  Meeting,  March  10th,  1872. 
How  many  pharmacists  would  believe  it  if  informed  that  the  drugs 
which  they  are  daily  handling  contain  from  10  to  18  per  cent,  of 
moisture,  which  they  lose  in  drying  ?  I  myself  could  scarcely  credit 
it  when  my  first  experiments  were  made,  and  thought  I  might  have 
lost  some  of  the  drug  between  the  repeated  weighings,  but  repetition 
of  the  experiments  always  confirmed  the  results  previously  obtained. 
Even  the  powders,  which  are  supposed  to  be  dry  or  very  nearly  so, 
lose  in  some  cases  from  8  to  10  per  cent,  of  moisture, 
I  have  experimented  with  a  large  number  of  drugs,  sufficient,  I  be- 
lieve, to  give  the  pharmacist  a  true  idea  of  the  amount  of  moisture 
contained  in  them,  and  the  results  show  conclusively  that  such  phar- 
maceutical preparations  like  syrups,  tinctures,  fluid  extracts,  &c, 
must  be  much  weaker  when  prepared  from  merely  air  dry  material 
than  when  made  from  anhydrous  drugs. 
The  process  of  drying  was  conducted  in  a  common  cooking  stove 
oven,  at  a  temperature  of  about  120°  Fahrenheit,  to  which  the  drug 
was  exposed  until  it  ceased  losing  any  more  weight.  By  being  exposed 
to  a  low  but  continuous  heat  the  loss  in  volatile  oil  may  probably  be 
greater  than  when  the  drug  is  dried  at  an  elevated  heat,  but  its  nor- 
mal amount  is  very  small  in  most  of  the  drugs  experimented  with,  so 
that  the  deduction  of  the  volatile  oil  expelled  in  drying  would  alter 
the  figures  below  but  little. 
The  dried  drugs  were  placed  in  a  room  for  two  weeks  and  then  re- 
weighed,  the  increase  of  weight  representing  the  amount  of  moisture 
reabsorbed  in  that  time.  While  these  experiments  were  made  the 
weather  was  cold  and  dry,  and  this  circumstance  doubtless  accounts 
for  the  smaller  percentage  absorbed  again,  while  in  a  few  case3  the 
loss  of  volatile  oil  may  explain  a  portion  of  the  deficiency. 
The  following  tables  show  the  loss  sustained  by  the  drugs  men- 
tioned, and  the  gain  in  weight  of  the  dried  articles  under  the  circum- 
stances mentioned  above : 
