ON  THE  RANCIDITY  OF  FATS. 
59 
Peru  No.  2  shows  symptoms  of  giving  way,  but  all  the  rest  are 
apparently  as  good  as  ever.  In  order  to  ascertain  the  actual 
condition  of  the  fats — to  try  whether  or  not  the  test  of  color 
could  be  relied  on — I  recovered  them  by  means  of  benzole 
from  the  No.  2  creasote  and  No.  2  pimento,  and  found  them 
react  perfectly  neutral  with  iodide  of  potassium,  notwithstand- 
ing they  had  been  purposely  kept  under  the  most  unfavorable 
conditions  for  upwards  of  twenty  months. 
The  action  of  creasote,  the  great  antiseptic,  is  not  difficult  to 
understand ;  but  whether  the  essential  oils  shared  its  power  to 
prevent  the  putrefaction  of  albumen  remained  to  be  proved. 
To  do  so,  I  prepared  a  filtered  solution  of  egg  albumen,  and  to 
2-ounce  portions  of  it,  placed  in  3-ounce  bottles,  I  added  two 
drops  of  each  of  the  essential  oils  I  had  used  with  the  ointments, 
dissolved  in  J  drachm  of  rectified  spirit.  One  portion,  mixed 
with  spirit  only,  was  placed  with  them  for  comparison.  They 
all  were  set  aside  in  the  situation  previously  occupied  by  the 
ointments.  The  unscented  albumen  became  putrid  in  twenty- 
eight  days  ;  the  other  specimens  are  still  good.  I  expect  them 
to  observe  the  same  order  in  this  experiment  as  in  those  with 
the  ointments.  I  may  add,  that  all  these  essential  oils  precipi- 
tate albumen,  some  more,  some  less. 
Having  succeeded  so  well  with  the  ointment  of  oxide  of  mer- 
cury, I  commenced,  January  22d  of  this  year,  to  try  similar 
experiments  on  pure  lard. 
Twelve  pounds  of  fresh  flare  were  completely  deprived  of 
flesh  and  membrane,  bruised  well,  washed  under  a  stream  of 
water,  and  placed  in  a  porcelain  vessel  over  a  water-bath.  As 
soon  as  one-third  was  liquefied,  that  portion  was  strained  and 
set  aside.  The  temperature  had  not  exceeded  140°.  This 
lard  I  shall  refer  to  as  No.  1. 
The  rest  was  kept  on  the  bath  one  hour  after  total  liquefac- 
tion, then  strained,  its  temperature  being  190p  ;  half  of  it  was 
set  aside  =  No.  2. 
The  remainder  was  gradually  heated  to  220°,  and  kept  at 
that  temperature  for  five  minutes  —  No.  3.  It  was  much  firmer 
than  either  of  the  preceding,  and  maintained  that  distinction 
after  being  stirred. 
Of  each  of  these  lards  I  set  aside,  in  willow  boxes,  three 
