316      ALCOHOLOMETRIC  SCALES  OF  RICHTER  AND  TRALLES. 
nesia,  and  the  Protoxide  of  Iron ;  those  of  the  leaves  to  be 
Tannin,  of  the  same  order  as  the  above,  Qhlorophylle,  a  Resinous 
extractive  matter,  and  salts  of  Potassa  and  Lime, 
ON  THE  ALCOHOLOMETMC  SCALES  OF  RICHTER  AND  TRALLES. 
To  the  Editor  of  the  American  Journal  of  Pharmacy  : — 
Dear  Sir — In  the  Journal  of  the  College  of  Pharmacy  for 
May,  1856,  I  observed  an  article  on  the  specific  gravity  of  alco- 
hol, which,  as  a  manufacturer  of  specific  gravity  apparatus,  at- 
tracted my  notice.  In  the  commencement  of  that  paper,  the 
dilemma  of  Mr.  C.  Mead  is  to  be  noted,  who,  purchasing  alcohol 
for  80  per  cent.,  finds  upon  trial  that  it  is  nearly  85  per  cent, 
by  weight  of  the  U.  S.  Dispensatory,  and  nearly  90  per  cent,  by 
measure,  according  to  Tralles'  tables  in  Ure's  Dictionary.  Cer- 
tainly there  appears  here  no  cause  of  complaint  on  the  part  of 
the  purchaser,  who  gets  a  better  article  than  he  contracted  for, 
an  accident  which  I  am  confident  does  not  often  occur  elsewhere. 
Mr.  M.  next  states,  that  in  his  trial  of  the  above  alcohol  he 
weighed  it  and  found  its  specific  gravity  to  be  -834  at  60°  F., 
meaning  of  course  that  an  accurately  made  1000  grain  specific 
gravity  bottle  held  only  834  grains  of  the  alcohol.  This  may  well 
be  called  the  experimentum  crucis,  surpassing  in  accuracy  all  other 
methods  of  ascertaining  the  specific  gravity  of  liquids.  Accord- 
ing to  that  observation,  there  can  be  no  doubt  but  that  his  con- 
clusions were  correct,  viz :  that  the  alcohol  he  purchased  was 
actually  nearly  85  per  cent,  by  weight,  or  nearly  90  per  cent,  by 
volume.  Mr.  M.  further  remarks,  that  he  is  quite  sure  that  the 
table  of  the  U.  S.  Dispensatory  is  not  the  standard  by  which 
distillers'  instruments  here  are  made.  If  by  the  distillers'  instru- 
ments, the  Berlin  hydrometers,  or  those  made  here  and  copied 
after  them,  are  meant,  then  Mr.  M.  is  likewise  correct,  and  we  are 
obliged  to  admit  that  the  Berlin  instruments  are  not  quite  so  in- 
fallible as  many  imagine  ;  unless  it  be  supposed  that  all  the 
printed  tables  given  in  the  various  works,  which  will  be  referred 
to  presently,  are  erroneous. 
In  Mr.  A.  P.  Sharp's  reply  to  Mr.  Mead,  it  is  stated,  that  ac- 
cording to  order  of  Congress,  the  percentage  of  alcohol  is  to  be 
measured  by  volume,  and  this  agrees  with  the  usage  of  all  manu- 
