Am.  Jour.  Pharm. 
April,  1910. 
Correspondence. 
187 
and  from  this  official  curve  the  correction,  for  any  temperature, 
could  be  determined  by  inspection,  thereby  conducing  to  absolute 
uniformity  in  this  particular. 
Finally,  what  is  the  melting  point  ?  Some  authorities  say  it  is 
that  temperature  at  which  the  substance  first  begins  to  melt ;  others, 
that  temperature  at  which  it  is  just  completely  melted;  others,  the 
mean  of  these  values  ;  and  still  others  say  that  it  is  not  a  point  at  all 
(except  in  theory)  but  a  range,  with  which  I  emphatically  agree. 
At  any  rate  it  should  need  no  argument  to  convince  that  here 
is  broad  opportunity  for  wide  divergence  ;  nor  to  induce  the  con- 
clusion that  if  standardization  of  this  constant  is  to  be  effective  a 
clear,  unmistakable  definition  of  the  melting  point  is  essential. 
With  regard  to  the  decomposing  point  I  am  personally  con- 
vinced that  it  should  never  be  used  as  a  test  of  purity,  and  this 
conviction  is  based  upon  experimental  evidence  with  several 
compounds. 
Anything  like  a  complete  treatment  of  the  melting  point  prob- 
lem, in  its  present  application  to  the  U.S. P.,  is  impossible  within  the 
limits  of  a  half-hour  discussion.  For  the  purpose  of  this  meeting 
it  seemed  more  desirable  to  briefly  outline  all  the  more  important 
phases  of  the  problem  than  to  attempt  a  very  detailed  discussion  of 
any  one  or  two. 
Note:  The  subject  of  this  paper,  and  the  work  that  has  recently 
been  done  in  the  Hygienic  Laboratory  on  U.S. P.  melting  points 
will  be  given  more  complete  and  detailed  treatment  in  a  Hygienic 
Laboratory  Bulletin  to  be  published  in  the  near  future. 
CORRESPONDENCE  ON  THE  RELATIVE  VALUE  OF 
MACERATION  AND  PERCOLATION. 
In  view  of  the  statements  contained  in  the  Presidential  address 
presented  by  Professor  Oldberg  to  the  members  of  the  American 
Pharmaceutical  Association  at  the  Los  Angeles  meeting,  on  the 
subject  of  maceration,  letters  were  sent  to  various  persons,  includ- 
ing both  retail  and  manufacturing  pharmacists,  asking  for  their 
opinion  on  the  relative  merits  of  maceration  and  percolation.  Ab- 
stracts of  the  replies  received  follow. — Editor. 
Prof.  H.  V.  Arny,  Cleveland,  writes :   I  beg  to  make  the  fol- 
