AmMa5;Sm'}  Estimation  of  Caseine.  1 21 
Mr.  W.  Sowerby,  the  Society's  secretary  at  that  time,  on  the  occasion  of  the 
fiftieth  anniversary  of  the  Society.  There  is  also  an  official  Guide  to  the  Gar- 
dens (London,  1900)  which  contains  a  number  of  interesting  photographs  of 
their  characteristic  features,  in  addition  to  an  excellent  popular  account  of 
the  Gardens  by  Mrs.  J.  B.  Sowerby.  More  recent  developments  still  are  briefly 
summarized  in  an  illustrated  booklet  issued  by  the  Council,  and  entitled 
"  The  Royal  Botanic  Society  of  London."] 
( To  be  continued. ) 
ESTIMATION  OF  CASEINE. — A  PRELIMINARY  STUDY.1 
By  H.  V.  Arny,  Ph.D.,  and  T.  M.  Pratt,  Ph.C. 
The  marked  need  for  a  simple  and  reliable  estimation  of  caseine 
is  apparent  to  all  chemists  doing  milk  analysis.  The  only  direct 
volumetric  process — that  of  Denige  (Jour.  Pharm.  et  Chem.y  Series  6, 
VII,  No.  1)  is  too  complicated  for  practical  purposes;  while  the 
generally  accepted  method  of  nitrogen  estimation  by  the  Kjehldahl 
process,  involving  as  it  does  digestion  with  sulphuric  acid  and  mer- 
cury, distillation  of  this  mixture  with  potassium  sulphide  and  alkali 
and  final  titration  of  the  distillate  for  ammonia  with  volumetric 
solution  of  sulphuric  acid,  and  that  only  after  separation  of  the 
lactalbumin  and  globulin,  is  even  more  intricate  and  time  consuming. 
Needing  a  quick  process,  one  of  us  tried  the  simple  expedient  of 
noting  the  amount  of  potassa  alum  required  for  the  complete  pre- 
cipitation of  caseine  from  milk,  and  the  results  on  rough  estimations 
were  so  satisfactory  and  pointed  so  convincingly  to  the  fact  that 
alum  combined  with  caseine  in  molecular  proportions,  that  attempt 
was  made  to  bring  the  process  within  a  limit  of  reasonable  accuracy. 
The  scheme  consisted  of  slowly  dropping  alum  solution  from  a 
burette  into  warm  diluted  milk,  until  precipitation  was  complete. 
Experience  shows  that  uniform  heat  was  essential  for  definite  results, 
since  cold  milk  requires  more  alum  for  precipitation  than  does  warm, 
and  that  in  proportion  to  heat  employed. 
The  weakness  of  this  process  lay  in  the  difficulty  in  deciding  the 
point  of  complete  precipitation.  Yet,  it  is  a  striking  fact  that  of 
1,000  samples  examined  during  two  years,  694  required  29  to  3-1  c.c. 
concentrated  alum  solution  for  precipitation  of  25  c.c.  of  milk,  while 
1  Presented  at  the  Atl  antic  City  meeting  of  the  American  Pharmaceutical 
Association,  September,  1905,  and  contributed  by  the  authors. 
