Am.  Jour.  Pharm.  | 
fc  February ,^1909.,  J 
Estimation  of  Alcohol. 
69 
the  calculated  value.  Alcohol  was  determined  as  follows :  100  c.c. 
of  the  liquid  were  diluted  with  60  to  75  c.c.  of  water,  about  95  c.c. 
distilled  into  the  flask  originally  used  for  measuring,  and  the  content 
brought  to  the  mark.  The  specific  gravity  was  determined  and  the 
alcohol  value  obtained  from  the  tables.11  About  one-half  of  the 
distillations  were  made  from  a  250  c.c.  distilling  flask  having  a  de- 
livery at  a  mean  distance  of  about  16  cm.  from  the  surface  of  the 
boiling  liquid.  The  remainder  were  made  from  a  250  c.c.  flask 
with  delivery  about  10  cm.  from  the  surface  of  the  liquid.  The 
results  obtained  from  the  two  styles  of  flask  were  not  very  appreci- 
ably different,  although  the  losses  in  alcohol  from  the  calculated 
values  were  slightly  greater  in  the  flask  with  the  longer  neck. 
Some  diluted  alcohol  was  prepared  by  mixing  equal  volumes  of 
distilled  water  and  alcohol.  After  standing  forty-eight  hours  to 
insure  maximum  contraction  the  specific  gravity  was  taken  in 
triplicate.  The  results  were  0.936304,  0.936423  and  0.936066,  with 
a  mean  of  0.936264  corresponding  respectively  to  the  following  per- 
centages of  alcohol:  49.028,  48.965  and  49.150;  mean,  49.048.  The 
greatest  difference  in  specific  gravity  was  0.000357  corresponding  at 
this  concentration  to  a  difference  of  0.185  per  cent,  of  alcohol.  The 
mean  value,  49.048  per  cent.,  was  assumed  to  be  the  correct  one  and 
all  calculations  in  succeeding  dilutions  are  based  upon  it. 
The  alcohol  in  the  above  mixture  was  determined  twice.  Sample 
A:  specific  gravity,  0.936825;  alcohol,  48.756  per  cent.;  loss,  0.292 
per  cent.  Sample  B  :  specific  gravity,  0.93673 1 ;  alcohol,  48.82  per 
cent. ;  loss,  0.228  per  cent.  Mean  loss,  0.26  per  cent.  Although 
great  precautions  were  taken  to  prevent  leakage  through  the  joints  of 
the  apparatus  there  was  an  appreciable  loss. 
A  sample  of  diluted  glycerin  was  prepared  by  mixing  100  c.c.  of 
U.  S.  P.  glycerin  with  400  c.c.  of  distilled  water.  The  specific 
gravity  of  this  mixture  was  then  determined  and  the  percentage  of 
glycerin  calculated  from  Nicol's  tables.12  Specific  gravity,  1. 0571 5; 
glycerol,  23.25  per  cent,  by  weight. 
Two  samples  of  this  diluted  glycerin  of  100  c.c.  each  were  then 
distilled  as  for  alcohol  by  the  usual  method  and  the  specific  gravity 
of  the  respective  distillates  taken  at  200.  The  results  were  1.0000003 
and  1.000113;  mean  1.000056  corresponding  to  0.0241  per  cent. 
11 U.  S.  Dept.  Agr.,  Bur.  Chem.,  Bull.  107,  p.  203. 
12  Pharm.  Jour.  Tr.  [3],  18,  302  (1887). 
