n6    Estimation  of  Alcohol  in  Spirituous  Liquors,  {^ebmary,15!1^™' 
aqueous  potassium  carbonate  solution  (middle  layer)  contains 
0.00275  vol.  of  alcohol  hydrate  per  Cc. 
The  composition  of  the  alcohol  hydrate  was  determined  by 
density  determinations  by  weighing,  as  well  as  by  the  glass  hydrom- 
eter at  1 5. 6°  C.  The  results  for  specific  gravity  were  0.81961  and 
0.8200  respectively,  corresponding  with  94.04  and  93.92  per  cent, 
of  alcohol  by  volume.  The  formula  4C2H5OH,  H20,  assigned  to 
the  hydrate  requires  94.061  per  cent,  of  absolute  alcohol  by  vol., 
91.089  per  cent,  by  weight.  The  alcohol  hydrate  does  not  leave 
any  solid  residue  on  evaporation,  showing  that  it  does  not  dissolve 
potassium  carbonate.  The  coefficient  of  expansion  of  the  alcohol 
hydrate  as  determined  by  a  weight  thermometer  was  0.001076;  cal- 
culated theoretically  by  extrapolation  from  Tralles'  Table  II.  the 
value  0.001068  was  obtained. 
The  formula  obtained  for  calculating  the  percentage  of  alcohol 
as  the  results  of  experiment  and  on  theoretical  grounds  is  as  fol- 
lows:  Percentage  of  alcohol  —  (V  -\-v  X  0.00275)  [1 — 0.001068  (t 
— ■  15.6)  ]  X  0.7936  X  94.06 -f-  W ,  where  V  =  volume  of  alcohol 
hydrate  directly  read  off  in  graduated  tube  in  Cc,  v=-  volume  of  the 
saturated  potassium  carbonate  solution  (middle  layer),  t  =  tempera- 
ture observed  during  the  experiment  in  °'C,  W  =  weight  of  the 
sample  taken  in  Gm.,  0.00275  is  the  solubility  (in  Cc.)  of  the  alcohol 
hydrate  per  Cc.  of  the  saturated  potassium  carbonate  solution,  as 
actually  found  by  experiment,  0.001068  is  the  apparent  coefficient 
of  expansion  of  the  alcohol  hydrate,  0.7936  is  the  specific  gravity 
of  absolute  alcohol  (i5.6°/i5.6°  ;  it  is  assumed  that  the  graduation 
of  the  glass  apparatus  used  had  been  carried  out  at  15.60  C),  and 
94.06  is  the  percentage  by  volume  of  absolute  alcohol  present  in  the 
alcohol  hydrate  liberated  (upper  layer).  (This  corresponds  to  per- 
centage composition  by  weight,  alcohol  91.089,  water  8,911,  the  cor- 
responding density  being  0.8195 14.) 
If  the  volume  of  saturated  potassium  carbonate  solution  is  less 
than  2  Cc.  the  correction  for  the  solubility  of  alcohol  hydrate  in 
potassium  carbonate  solution  may  be  dispensed  with  as  it  does  not 
appreciably  affect  the  result. 
In  order  further  to  verify  the  formula  given  above,  5  Cc.  of 
Merck's  alcohol  (marked  "absolute  alcohol,  sp.  gr.  0.795")  was 
mixed  with  saturated  potassium  carbonate  solution,  some  solid  car- 
bonate also  being  added.  The  strength  of  the  alcohol  as  calculated 
by  our  formula  was  99.46  per  cent. ;  the  specific  gravity  observed 
