Am.  Jour.  Pharm. 
Jan.,  1879. 
Permanent  Rennet-Essence. 
37 
gold  are  precipitated,  but,  by  the  addition  of  a  little  pure  nitric  acid, 
are  dissolved,  and,  if  the  solution  be  set  aside,  crystals  similar  to  those 
described  may  be  obtained. 
Nitrate  of  silver  containing  gold  may  be  purified  by  fusion.  On 
dissolving  the  cake  in  water  the  gold  will  be  deposited,  or  may  be 
removed  by  filtration  through  asbestos. —  Can.Phar.  Jour.,  Nov.,  1878. 
PREPARATION  of  PERMANENT  RENNET-ESSENCE. 
By  H.  Soxhlet. 
For  the  preparation  of  concentrated  solutions  only  dried  calves' 
stomachs  are  suitable,  and  those  which  have  been  blown  out  with  air 
and  dried  as  quickly  as  possible  are  best.  The  small  stomachs  of  the 
youngest  animals  are  richest  in  ferment.  Fresh  stomachs  are  useless 
for  preparing  a  concentrated  essence,  as  they  yield  a  thick  jelly,  which 
by  filtering  gives  only  a  small  quantity  of  liquid.  Concentrated  extract 
prepared  from  stomachs  after  14.  days  is  light-yellow  in  color,  whilst 
that  prepared  after  6  to  8  months'  storage  of  the  stomachs  is  dark- 
brown.  This  results  from  slight  decay  of  the  stomach,  and  as  the 
color  does  not  affect  the  usefulness  of  the  product  it  is  advisable  to  use 
stomachs  which  have  been  stored  for  at  least  three  months.  The 
portion  of  the  stomach  without  folds,  the  Portio  pylorica,  is  cut  away, 
as  it  is  poor  in  ferment. 
Acid  liquids  are  usually  employed  for  extracting,  as  they  seem  to 
produce  richer  solutions,  but  this  is  only  because  they  act  more  quickly 
at  first  than  water  alone.  Hydrochloric  acid  containing  o*i  and  0*2 
per  cent,  of  acid  in  two  days  gave  extracts  twice  as  rich  in  ferment  as 
an  aqueous  one,  but  after  eight  days  all  three  solutions  were  equally 
strong.  A  little  thymol  was  added  to  prevent  decomposition  during 
the  experiment.  When  the  temperature  is  raised  to  300  to  350  water 
acts  more  rapidly  than  the  acid,  and  the  solution  is  richer  than  that 
produced  by  acid  at  the  ordinary  temperature. 
Attempts  were  made  to  produce  concentrated  solutions  by  means  of 
dilute  acids,  but  without  success.  A  0*3  per  cent,  solution  of 
salicylic  acid  gave  a  liquid  which  was  quite  fresh  after  twelve  months, 
but  after  only  two  months  its  activity  had  fallen  off  to  the  extent  of 
one-half. 
A  series  of  experiments  made  with  solutions  of  common  salt  con- 
