Ami)e2"ri92i.arnx  ^    Lactometer  and  Fat -in  Milk  Control.  819 
are  so  generally  used  that  instead  of  the  analyst  going  to  the  for- 
mulae themselves  or  to  a  table  of  values  derived  from  them,  slide 
rules  are  available  for  the  necessary  calculations.4  Some  of  the 
milk  formulae  that  are  most  extensively  used  date  back  thirty  to 
thirty-five  years  and  have  survived  the  scrutiny  of  critics  and  the 
proof  of  practice.  Two  formulae  of  which  this  may  be  said  are 
( 1 )  the  formula  5  connecting  the  percentage  of  total  solids  T  with 
the  lactometer  reading  L  and  the  percentage  of  fat  F : 
T  =  y4L+%F  =  o.25L+i.2F    (1) 
and  (2  )  the  formula  6  connecting  the  mean  specific  gravity  pf  the 
total  solid  matter  m  with  the  specific  gravity  of  the  milk  G  and 
the  percentage  of  total  solids  T  contained  in  it.  The  removal  of  fat 
or  the  addition  of  skimmed  milk  raises  this  mean  specific 
gravity;  the  first,  because  it  removes  some  solids  that  are  lighter 
than  water,  the  .second,  because  it  increases  the  proportion  of  solids 
that  are  heavier  than  water.  The  relation  between  this  mean  specific 
gravity  of  the  solids  and  the  other  values  in  a  milk  can  be  and  has 
been  clearly  demonstrated  to  be  quantitative.7    This  relation  has 
between  pure  and  adultered  milk.  As  in  the  early  use  of  most  milk  formulae, 
"subsequent  experiences  (between  1909  and  1914)  showed  that  "for  prac- 
tical purposes"  certain  changes  were  desirable  in  the  application  of  them. 
4  Richmond's  "Milk  Scale"  and  Ackermann's  "Automatic  Reckoner." 
5  This  simple  form  is  often  called  Richmond's,  or  Richmond  and  Hehner, 
or  Babcock's  formulae.  As  a  matter  of  fact  it  is  a  simpler  form  of  expression 
that  became  apparent  when  more  complicated  formulae  were  applied  and  the 
tabulated  results  then  compared.  See  Richmond's  Dairy  Chemistry,  2d  Ed., 
1914,  p.  69 ;  and  Shaw  and  Eckles,  Bull.  134,  U.  S.  Dept.  Agr.,  Bur.  of  Animal 
Ind.,  191 1.  Richmond  and  Hehner's  formulae  (Analyst,  13,  p.  26,  1888), 
T  =  0.254  G  +  1. 164  F.  which  approximates  closely  to  T  =  %  G  +  %  F 
Richmond  later  derived  a  new  formula  because  the  previous  formulae  "were 
derived  from  analyses  to  which  objection  could  be  taken";  so  that  Richmond's 
T 
formula  is  T  =  0.2625  —  +  1.2  F,  which  has  been  found  to  be  expressed  bv 
G 
G  6 
the  simpler  formula,  T  =  —  +  —  F  +  .14;  and  this  is  the  formula  on  which 
4  5. 
Richmond's  milk  scale  rests.  In  this  country  it  is  customary  to  drop  the  con- 
stant, as  suggested  by  Patrick  (see  Leffman,  Analysis  of  Milk  and  Milk  Prod- 
ucts 1915,  p.  21)  ;  and  after  so  doing,  the  formula  is  frequently  called  Bab- 
cock's formula.  Babcock's  papers  are  in  the  8th  and  12th  Ann.  Rep.  Wisconsin 
Agr.  Exp.  Sta.,  1891  and  1895-  See  Allen's  Com.  Org.  Anal,  4th  Ed.,  Vol.  VIII. 
p.  163. 
6  Known  as  Fleischmann's  formula,  which  dates  back  in  its  beginnings  to 
1882-85  (Jour,  fur  Landwirtschaft,  30,  p.  293;  33,  p.  251.). 
7  For  demonstration,  see  Richmond's  Dairy  Chemistry,  p.  64. 
