THE  AMERICAN 
JOURNAL  OF  PHARMACY. 
APRIL,  1881. 
ON  SPECIFIC  GRAVITY  and  INCREASE  IN  YOLUMEv 
By  William  Clay  Smith,  Ph.G. 
From  an  Inaugural  Essay . 
When  solids  are  dissolved  in  liquids  there  is  an  increase  in  volume^- 
and  a  number  of  experiments  were  undertaken  to  ascertain  this  increase 
in  regard  to  some  chemicals  of  the  Pharmacopoeia.  The  method  of 
conducting  the  experiments  was  as  follows : 
A  graduated  tube  was  tal^en,  and  in  this  was  placed  20  cubic  centi- 
meters of  distilled  water,  the  temperature  being  carefully  noted  and 
maintained  as  near  60  °F.  as  possible ;  to  this  was  added  a  weighed 
quantity  of  the  substance,  sufficient  to  form  a  nearly  saturated  solution ; 
after  solution  the  temperature  was  again  noted,  and  if  too  high,  was 
reduced  to  60°F.  and  the  volume  again  noted ;  for  example,  if  10 
grams  of  citric  acid  had  been  dissolved  in  20  cc.  of  distilled  water,  the 
volume  was  found  to  be  26 '3  cc,  showing  the  increase  to  have  been 
6*3  cc.  To  the  solution  thus  obtained  10  cc.  more  of  water  was  added, 
giving  a  solution  of  10  grams  of  substance  in  30  cc.  of  distilled  water. 
When  thoroughly  mixed  and  the  temperature  reduced  to  60  °F.,  it 
showed  the  increase  to  be  6*1  cc,  or  a  contraction  of  0*2  cc;  when  10 
cc  more  of  water  was  added  the  volume  was  further  reduced,  giving 
as  a  result  5*9  cc.  as  the  increase,  or  a  contration  of  0*2  cc.  for  each  10 
cc.  of  water  added.  This  contraction  of  volume  was  found  to  occur 
in  almost  every  instance. 
There  was  also  a  second  series  of  experiments  made  with  one-half 
the  quantity  of  each  substance  and  half  the  amount  of  water,  with  a 
view  of  confirming  the  first  experiments,  and  in  the  majority  of  cases 
the  result  was  the  same  or  within  a  fraction  of  one  per  cent.  In  those 
cases  where  the  difference  was  great  enough  to  suppose  that  there  had 
been  an  error  of  observation,  the  experiments  were  repeated  and  the 
results  accepted  which  corresponded  most  closely. 
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