ADeclmler?mh'}    Determination  of  Specific  Gravity.  595 
to  get  16  teaspoonfuls  ;  a' three-ounce  mixture  would  give  him  exactly 
what  he  wants. 
Professor  Wilcox's  comment  upon  the  domestic  measures  should 
be  widely  circulated.  He  says :  Spoons,  glasses,  and  cups  vary  so 
much  in  capacity  that  it  is  never  safe  to  prescribe  solutions  of  pow- 
erful drugs  to  be  measured  by  them.  The  use  of  glass  graduates, 
which  can  be  obtained  accurately  marked,  should  be  insisted  upon. 
NOTE  ON  THE  DETERMINATION  OF  SPECIFIC 
GRAVITY. 
By  Robert  A.  Hatcher,  M.D. 
The  accompanying  diagram  illustrates  a  method  of  taking  specific 
gravity  which  has  not  been  widely  used  (if,  indeed,  it  has  ever  been 
suggested),  with  an  ordinary  box  prescription  scale. 
A  beaker  containing  water  is  balanced  upon  the  scale,  and  having 
weighed  the  article  in  air,  it  is  then  suspended  so  that  it  is  wholly 
immersed  in  the  water  but  does  not  touch  the  bottom  of  the  beaker. 
m 
u 
Determination  of  Specific  Gravity  with  a  Prescription  Scale. 
The  weight  now  required  to  restore  the  balance  is  the  weight  of  the 
water  displaced,  and  it  equals  the  loss  of  weight  of  the  substance  in 
water.  The  specific  gravity  is  found  by  dividing  the  weight  in  air 
by  the  loss  of  weight  in  water,  the  result  being  the  specific  gravity 
sought. 
