252  Alcohol  Tables  of  Hehner  and  Pile.  {^'^\*uvm' 
The  first  general  observation  to  be  made  in  regard  to  these  tables  is 
that  for  ordinary  use  they  are  quite  too  voluminous.  Hehner's  table 
occupies  fourteen  pages  of  a  volume  which  should  contain  as  little 
superfluous  matter  as  possible.  A  table  extending  not  beyond  two 
pages  would  be  much  more  convenient  for  reference,  and  might  easily 
be  constructed  so  as  to  comprehend  more  than  the  present  table. 
Pile's  table,  published  in  the  February  number  of  the  "  Journal  of 
Pharmacy/'  is  equally  diffuse,  coinciding  indeed,  line  for  line,  with 
that  of  Hehner.  The  principle  on  which  these  tables  are  constructed 
is,  in  fact,  radically  vicious.  A  difference  of  *0001  in  specific  gravity 
in  a  spirit  containing  eighteen  per  cent,  (vol.)  absolute  alcohol  will 
correspond  to  a  difference  of  one-tenth  of  one  per  cent.,  nearly,  in 
strength,  whereas  the  same  difference  in  specific  gravity  in  a  spirit  con- 
taining ninety-nine  per  cent,  of  alcohol,  will  indicate  a  difference  in 
strength  only  one-fifth  as  great.  The  second  page  of  the  Pharma- 
copoeia table  thus  contains  volume  percentages,  ranging  from  9  to  23, 
while  the  thirteenth  page,  with  the  same  number  of  figures  covers  only 
the  interval  between  93 \  and  97  per  cent.,  and  that,  too,  in  a  portion 
of  the  table  which  one  has  very  rarely  occasion  to  consult.  One  is 
reminded  of  a  map  drawn  on  Mercator's  projection,  on  which  the  frozen 
polar  regions  are  expanded  out  of  all  proportion  to  their  importance. 
The  labor  of  interpolating  values  between  those  of  the  ordinary 
tables  is  in  itself  trifling,  and  it  may  be  reduced  to  a  minimum  by 
adding  a  column  of  differences,  or  still  better,  a  column  containing  the 
factor  corresponding  with  a  difference  of  *0001  in  specific  gravity 
between  consecutive  terms,  and  for  practical  purposes,  the  necessary 
subtraction  and  multiplication  could  be  made  mentally,  in  less  time 
than  is  now  required  to  turn  over  the  leaves  in  search  of  the  required 
figure. 
One  important  feature  is  conspicuously  absent,  which  ought  by  all 
means  to  form  a  part  of  any  complete  alcoholometrical  table.  I  refer 
to  the  temperature  corrections  which  one  has  constantly  to  employ  in 
practice. 
These  errors  of  redundancy  and  deficiency  are  common  to  both  the 
tables.  We  come  now  to  a  comparison  between  them  on  the  vital 
point  of  the  relative  and  absolute  accuracy  of  their  figures.  In  gene- 
ral it  may  be  said  that  in  both  Hehner's  and  Pile's  tables,  the  mathe- 
matical computations  have  been  performed  with  commendable  pre- 
cision.   I  have  not  had  the  time  to  examine  all  the  figures,  but  it  is 
