ALCOHOLOMETKIC  SCALES  OF  RICHTER  AND  TRALLES.  317 
facturers  and  dealers,  who  always  sell  by  measure  and  not  by 
weight.  By  not  paying  proper  attention  to  this  fact,  many 
vexatious  disputes  arise  between  buyers  and  sellers,  one  selling 
by  measure  the  other  testing  by  weight,  and  finding  the  percent- 
age much  less  than  it  was  represented  to  be. 
We  are  also  informed  that  the  U.  States  have  adopted  Gay 
Lussac  or  Tralles'  alcoholometer,  meaning,  I  suppose,  the  scales 
graduated  according  to  the  experiments  of  those  observers. 
These  scales,  however,  are  not  identical,  being  the  results  of 
independent  experimenters  ;  Tralles'  scale  being  made  for  the 
English  Government  excise,  and  Gay  Lussac's  for  that  of  France. 
Besides  the  discrepancies  arising  from  the  experiments  themselves, 
the  normal  temperature  of  the  two  observers  are  different,  Tralles' 
scale  indicating  the  percentage  at  60°  F.  and  Gay  Lussac  the 
same  at  59°.  The  variation  from  this  case  is  certainly  not  very 
important,  but  is  farther  increased  by  the  fact  of  Tralles'  taking 
water  at  its  greatest  density  (39i°  F.)  at  1*000,  thus  making 
zero  or  commencement  of  his  scale  to  equal  »9991,  while  Gay 
Lussac  reckons  the  density  of  water  at  59°  F.  to  equal  1*000. 
In  all  the  instruments  I  have  seen,  the  zero  of  Tralles'  scale 
commenced  at  1«000  sp.  grav.;  this  does  not  interfere  with  their 
accuracy,  for  the  specific  gravities  of  all  the  percentages  being 
increased  in  the  same  ratio,  by  dividing  by  .9991,  or  which  is 
nearly  the  same,  adding  -0009  we  obtain  a  corrected  scale  begin- 
ning at  1-000. 
The  greatest  difference  between  the  two  scales  is  about  1  per 
cent.,  varying  in  different  parts  of  the  scale,  and  from  some  ob- 
servations I  have  made,  I  should  judge  that  the  name  44  Gay 
Lussac  "  and  "  Tralles  "  is  used  indiscriminately. 
The  Berlin  made  alcoholometers,  when  examined  with  refer- 
ence to  Tralles'  tables,  are  in  general  very  reliable;  I  have  tested 
many  of  them  with  the  specific  gravity  bottle  at  various  points 
of  the  scale  and  found  them  correct.  The  table  of  Tralles  re- 
ferred to,  may  be  found  in  Ure's  Chemical  Dictionary,  Booth's 
Encyclopedia,  Muspratt's  Chemistry,  &c;  those  of  Gay  Lussac  in 
Gmelin's  Hand-Book  of  Chemistry,  vol.  i.,  and  in  Booth's  work* 
The  corrections  for  temperature  generally  adopted,  namely, 
to  increase  the  observed  percentage  1  degree,  for  every  5  degrees 
the  thermometer  stands  below  60°  F.,  and  to  decrease  the 
