ON  SPECIFIC  GRAVITY  OF  ALCOHOL. 
211 
to  be  used  with  the  Hydrometer,"  and  the  "  Manual  for  Inspec- 
tors of  Spirits."  The  latter  is  divided  into  three  parts,  as  fol- 
lows :  A  table  showing  the  true  per  cent.,  by  volume,  of  any 
spirits  or  alcohol  varying  in  temperature  from  20  to  100°  Fah- 
renheit. The  second  part  is  to  tell  the  true  value  when  the  quan- 
tity or  volume  of  the  spirits  is  known,  but  the  temperature  being 
above  or  below  the  standard,  60°  F.  The  third  table  is  a  com- 
bination of  the  other  two, 
The  standard  of  proof  is  fifty  per  cent,  by  volume  or  measure, 
that  is  to  say,  one  pint  of  absolute  alcohol  and  one  pint  water 
makes  proof  spirits,  which  is  fifteen  degrees  weaker  than  the 
London  proof:  or  by  Sykes'  Hydrometer,  specific  gravity  936. 
Second  proof  is  five  degrees  stronger,  52^  per  cent,  alcohol,  and 
has  a  specific  gravity  of  931.  Third  proof  10  degrees  stronger, 
55J  per  cent,  alcohol,  specific  gravity  925.  Fourth  proof  15 
degrees  above  proof,  53  per  cent,  alcohol,  specific  gravity  920, 
and  is  London  proof. 
The  best  instrument,  the  cheapest,  and  the  one  the  United 
States  have  adopted  for  all  the  custom  houses  as  their  standard 
for  testing  the  strength  of  spirits  from  one  to  100  per  cent.,  is 
Gay  Lussac,  or  Tralle's  hydrometer  or  Alcoholmeter,  made  by 
Luhme  &  Co.  and  Greiner,  of  Berlin.  They  have  been  tested 
by  the  most  accurate  balances,  and  found  the  most  reliable,  as  the 
common  ones,  of  brass,  copper  and  silver,  are  liable  to  oxydation 
and  corrosion,  which  of  course  affects  their  accurac}^  They  are 
made  with  a  thermometer  in  the  bulb,  the  degrees  of  which  either 
correspond  with  the  graduation  of  the  instrument,  or  a  Fahren- 
heit. If  the  former  and  the  mercury  stands  at  0,  and  the  stem 
indicates  80  per  cent,  alcohol,  that  is  the  true  per  cent.  If  it 
should  stand  at  one  degree  below  0,  the  true  per  cent,  would  be 
81,  as  the  alcohol  would  be  too  cold  ;  and  if  at  one  degree  above, 
the  true  per  cent,  would  be  79,  as  it  would  be  too  warm.  For 
every  degree  above  or  below,  one  per  cent,  is  to  be  added  or 
subtracted. 
If  they  have  the  Fahrenheit  scale  in  the  bulb,  every  five  de- 
grees above  or  below  60°  makes  a  difference  of  one  per  cent.,, 
using  the  same  rule  as  above,  adding  when  below  and  subtracting 
when  above  G0°. 
This  instrument  I  think  of  great  importance  to  pharmaceutists. 
