26 
Note  on  Specific  Gravity. 
f  Am.  Jour.  Pharm. 
I     January,  1899. 
If  an  ash  must  be  recorded  in  the  summary,  the  proper  material 
to  estimate  it  in  is  the  dried  residue  left  after  the  action  of  all  the 
solvents  employed  in  course  of  the  analysis.  There  may  not  be  any 
ash  in  some  cases,  at  this  point  of  the  analysis.1 
NOTE  ON  SPECIFIC  GRAVITY. 
By  T.  S.  Wiegand. 
It  may  be  thought  strange  by  some  that  a  subject  taught  so  fully 
in  our  schools  and  text-books  should  be  brought  before  the  atten- 
tion of  this  meeting,  but  the  common  things  of  every-day  life  and 
use  are  those  we  should  understand  and  study  most  carefully,  and 
in  this  opinion  we  are  supported  by  the  most  painstaking  scientists 
and  pharmacists  of  all  countries.  My  attention  was  drawn  to  the 
subject  when  recently  reading  one  of  the  most  recent  and  best  trea- 
tises on  pharmacy,  by  a  method  of  taking  the  specific  gravity  of 
substances  lighter  than  water,  as  it  was  there  described,  credited  to 
Mr.  Symonds  and  published  in  the  London  Pharmaceutical  Journal 
and  Transactions,  ser.  3d,  xix,  vol.  1 884.  As  the  method  is  one  with 
which  I  had  long  been  familiar  and  was  fully  explained  by  the  late 
eminent  Dr.  Robert  Hare,  formerly  professor  of  chemistry  in  the 
University  of  Pennsylvania,  I  referred  to  his  treatise  upon  chemical 
philosophy,  published  in  1828,  and  there  found  it  described  fifty-six 
years  before  the  Mr.  Symonds  paper  appeared  in  the  above-named 
periodical. 
The  readiness  with  which  this  method  may  be  performed  makes 
it  strange  that  it  has  not  been  taught  more  generally  in  the  text- 
books. The  process  is  simply  to  suspend  a  glass  funnel  to  a  scale 
pan  and  let  it  be  immersed  just  below  the  surface  of  the  water  in  a 
vase  below  the  scale  pan,  after  it  is  immersed  bring  it  to  equilibrium, 
and  then  thrust  the  body,  the  sp.  gr.  of  which  is  desired  under 
the  funnel,  then  restore  the  equilibrium  and  note  the  weight  neces- 
sary to  effect  this,  which  added  to  the  weight  of  the  light  body,  is 
to  be  divided  into  the  weight  of  the  light  substance  in  air — this  will 
give  the  sp.  gr.  of  the  light  body. 
[l  In  Dragendorff's  Plant  Analysis,  which  is  the  work  generally  employed 
as  a  guide  in  carrying  on  the  proximate  analyses  of  plants,  he  states  under 
the  alcoholic  and  aqueous  extractions  that  the  weight  of  ash  should  be  sub- 
stracted  from  the  weight  of  the  total  residue  and  the  difference  reported  as 
the  amount  of  total  organic  matter  for  those  particular  solvents. — Editor.] 
