ikm.  Jour.  Pharm. ) 
Sept.,  1881.  J 
Estimation  of  Peptones. 
463 
1  to  16,000:  opalescent  and  yellow. 
1  to  32,000 :  little  opalescence  and  pale  yellow. 
h.  Experiments  tvith  Carbolic  Acid :  In  these  experiments  the  solu- 
tions became  by  boiling  clear,  except  with  the  solution  of  1  to  1,000, 
which  on  cooling  was  slightly  turbid  and  colored  more  or  less  yellow, 
according  to  the  state  of  dilution.  Nitric  acid  gives  on  warming  very 
useful  reactions  to  distinguish  thymol  from  carbolic  acid,  unless  the 
latter  acid  should  not  be  in  a  concentrated  solution,  as  the  nitric  acid 
causes  a  turbidity. — Phar.  Jour.  Trans.,  July  9,  1881. 
THE  ESTIMATION  OF  THE  PEPTONES. 
By  T.  Defresne. 
Since  the  appearance  of  peptones  in  therapeutics  they  have  been  the 
object  of  general  attention.  As  inquiries  are  continually  made  as  to 
the  character  of  peptone  preparations  and  as  to  the  means  of  estimat- 
ing their  value,  the  following  notes  upon  the  subject  may  be  found 
useful. 
Several  methods  have  been  proposed  for  the  estimation  of  the  pep- 
tones, such  as  the  density,  precipitation  by  absolute  alcohol  and  the 
determination  of  the  ash  and  of  the  nitrogen.  But  it  may  be  affirmed 
without  hesitation  that  these  processes  have  been  put  forward  hastily, 
the  limits  of  their  exactitude  having  been  neither  studied  nor  deter- 
mined by  their  authors. 
Before  proceeding  to  the  estimation  of  any  peptone  it  is  of  the 
titmost  importance  to  examine  it  qualitatively.  If  this  preliminary 
work  be  omitted,  the  subsequent  estimations  may  be  falsified  by  sub- 
stances foreign  to  the  peptone,  which  have  been  introduced  with  the 
object  of  facilitating  its  preservation  or  of  constituting  it  a  complete 
aliment,  or  with  the  less  satisfactory  design  of  making  up  a  deficiency 
of  peptone. 
The  value  of  density  as  an  indication  is  but  small,  because  of  the 
gelatin,  glucose  and  glycerin  which  may  be  met  with  in  the  solutions. 
It  ought  therefore  to  be  rejected. 
The  process  which  consists  in  precipitating  the  peptone  by  absolute 
alcohol  gives  rise  to  two  kinds  of  errors,  according  to  the  conditions 
under  which  it  is  employed.  It  allows  on  the  one  hand  the  estima- 
tion as  peptone  of  the  gelatin  which  is  certainly  precipitated,  and  on 
