330  Weights  and  Measures  in  Liquid  Preparations.  {Amjuiy^'i^7harm 
error  in  weighing  liquids  as  in  measuring  them ;  in  fact,  the  question 
of  accuracy  on  either  side  resolves  itself  into  a  personal  equation,  and 
a  careless  operator  will  be  just  as  likely  to  be  loose  and  slovenly  in 
using  his  weights  as  he  would  in  filling  his  graduate.  But  it  has 
been  urged  that  liquids  change  their  volume  according  to  their  tem- 
perature— heat  expanding  them  and  cold  contracting  them — and 
hence  an  ounce  of  liquid  measured  in  the  winter  time  will  be  greater 
than  one  measured  in  the  summer  time.  This  is  a  physical  fact  that 
cannot  be  gainsay ed,  yet  it  must  be  admitted  that  the  amount  of  vari- 
ation is  trifling  and,  when  we  regard  the  present  methods  of  adminis- 
tering medicines,  unworthy  of  consideration. 
The  plea  of  greater  accuracy  in  making  liquid  pharmaceutical 
preparations  when  they  are  weighed,  receives  a  severe  practical  check 
when  we  reflect  that  a  large  proportion  of  the  analytical  chemists  of 
to-day  rightly  use  volumetric  estimation  in  their  every-day  work. 
Now,  if  these  conspicuous  apostles  of  accuracy,  who  have  done  so  much 
to  aid  the  sciences  of  chemistry  and  pharmacy,  cheerfully  disregard 
the  variations  due  to  change  in  volume  by  expansion  and  contraction 
in  their  standard  solutions,  and  yet  be  able  to  make  trustworthy 
analyses,  so  that  they  are  willing  to  depend  upon  the  number  of  cubic 
centimetres  of  test  solution  which  drop  from  their  burettes  to  their 
beakers,  how  utterly  insignificant  does  this  variation  appear  when 
applied  to  the  work  of  the  pharmacist,  for  he  makes  tinctures,  fluid 
extracts  and  syrups  which  are  to  drop  or  pour  from  bottles  or  tea- 
spoons into  stomachs  containing  more  or  less  digested  dinners. 
Then  again  if  the  plea  of  greater  accuracy  in  favor  of  weighing 
pharmaceutical  liquids  is  to  be  effective,  a  number  of  far  more  impor- 
tant questions  must  be  considered  and  met.  The  galenical  prepara- 
tions of  to-day  vary  in  strength  for  several  reasons,  drugs  contain  dif- 
ferent amounts  of  moisture  and  no  hygroscopic  standard  has  ever  been 
determined  upon ;  this  variation  can  easily  amount  to  ten  per  cent. 
The  quality  of  the  drug  used  in  these  preparations  except  in  one  or  two 
cases  is  at  present  determined  by  the  conscience  and  character  of  the 
operator,  no  officinal  standard  having  been  adopted,  and  it  is  doubtful 
if  reliable  methods  of  fixing  standards  for  all  galenical  preparations 
can  ever  be  developed.  In  view  of  these  facts  does  it  not  appear  that 
the  system  of  measuring  liquids,  particularly  if  standard  measures  are 
carefully  used,  is  far  more  convenient,  practical,  and  useful  for  the  re- 
tail pharmacist  than  that  of  weighing? 
