Am  Jour.  Pharm 
April,  1875. 
Pharmaceutical  Colleges  and  Associations,  19 
tion  of  a  lead  plaster  made  with  one  part  of  litharge  to  two  parts  of  olive  oil  as 
answering  more  the  general  requirements. 
In  the  discussion  which  followed  the  reading  of  this  paper,  views  were  expressed 
by  different  speakers  which  were  directly  opposite  each  other.  While  some  main- 
tained that  all  the  water  and  glycerin  should  be  removed,  others  appeared  to  be  in 
favor  of  leaving  the  glycerin  in  the  plaster.  While  some  advocated  the  complete 
saponification  of  the  fat,  others  favored  a  slight  excess  of  the  latter,  which  would  keep 
the  plaster  pliable  for  years  ;  but  the  liability  of  such  a  plaster  to  become  rancid  was 
mentioned,  whereby  it  is  rendered  unfit  for  use  in  the  preparation  of  neutral  cerate. 
It  was  stated,  upon  the  authority  of  Mr.  Squire,  as  expressed  in  his  "  Companion  to  the 
British  Pharmacopoeia,"  that  the  plaster  answered  only  when  made  with  the  best 
Italian  olive  oil,  and  that  it  was  not  satisfactory  if  Gallipoli  or  Spanish  oil  was  used  5 
the  experience  of  others  did  not  seem  to  coincide  with  this.  The  importance  ot 
using  a  good  quality  of  litharge  was  referred  to  as  being,  essential  for  obtaining  a 
good  plaster  with  even  the  best  olive  oil.  The  subject  was  deemed  of  importance 
so  as  to  invite  to  further  experiments,  and  to  the  collection  of  other  observations. 
A  paper  on  "  The  Estimation  of  Fat  in  Milk  "  was  read  by  Mr.  E.  L.  Cleaver. 
The  processes  most  generally  used  were  briefly  described  and  commented  upon,  lead- 
ing the  author  to  the  following  conclusions  : 
1.  Cold  ether  will  not  dissolve  out  the  entire  amount  of  fat  from  dry  milk  resi- 
dues. 
2.  Boiling  ether  will  not  dissolve  out  the  entire  amount  of  fat  from  milk  residues 
in  a  pasty  condition. 
3.  The  residues  should  be  in  a  state  of  fine  powder,  and  must  be  gently  boiled 
three  or  four  times  with  successive  portions  of  ether,  in  order  to  thoroughly  extract 
the  fatj  the  ether  being  always  passed  through  a  small  filter  before  evaporating. 
4.  During  evaporation  care  should  be  taken  not  to  allow  the  ether  to  enter  into 
ebullition. 
The  author's  process  maybe  briefly  stated  as  follows  :  10  grams  (or  C.  C.)  of 
milk  are  evaporated  in  a  small  dish  to  complete  dryness,  constantly  stirring  so  as  to 
obtain  a  fine  powder.  This  is  transferred  to  a  long,  narrow  tube,  the  dish  being 
rinsed  with  ether,  and  sufficient  ether  is  added  into  the  tube,  the  upper  portion  of 
which  is  wrapped  with  apiece  of  damp  cloth,  and  the  lower  end  dipped  into  a  water- 
bath,  a  gentle  ebullition  being  maintained  by  regulating  the  pressure  by  the  thumb 
of  the  operator  being  placed  upon  the  orifice ;  the  ether  solution  is  poured  through 
a  filter,  the  operation  repeated  three  or  four  times,  tlie  filter  washed  with  some  ether, 
and  the  filtrate  evaporated  by  a  current  of  air  from  a  bellows  or  foot-blower,  com- 
pleting it  over  a  water-bath,  when  the  fat  may  be  weighed. 
Mr.  Urwick  called  attention  to  the  difference  of  quality  between  specimens  of 
milk  taken  from  different  depths  in  the  can,  after  the  milk  had  been  standing  for  an 
hour  or  two. 
Professor  Redwood  described  the  method  generally  followed  in  England,  and 
which  is  a  modification  of  Wanklyn's  process.  A  carefully  tared  and  well  glazed 
hemispherical  German  dish  is  marked  with  its  correct  weight  5  in  it  the  milk  is  evapo- 
rated to  complete  dryness,  stirring  well  with  a  glass  rod  rounded  at  both  ends,  so  as 
to  reduce  the  residue  into  a  perfectly  fine  granular  condition,  when  the  dish,  with 
the  residue,  is  weighed.  The  residue  is  exhausted  with  four  successive  portions  of 
ether,  the  dish  being  placed  upon  the  water-bath,  but  care  being  taken  to  avoid  boil- 
ing the  ether  5  the  contents  are  well  stirred,  and  any  larger  particles  of  the  solid  res- 
idue are  broken  down  with  the  glass  rod.  The  residue  subsides  with  great  facility  and 
very  quickly,  and  the  clear  ether  solution  is  poured  into  a  beaker  in  order  to  observe 
that  no  solid  particles  have  been  decanted.  The  dish  is  then  dried  by  heat  and 
weighed,  the  loss  sustained  by  the  treatment  with  ether  indicating  the  weight  of  the 
fat,  and  by  deducting  the  tare  of  the  dish  from  the  last  weighing,  the  amount  of  non- 
fatty  solid  residue  is  obtained.  The  ether  solution  is  poured  into  a  bottle  and 
when  sufficient  has  accumulated,  the  ether  is  recovered  by  distillation.  The  advan- 
tages of  this  process  are,  that  a  number  of  assays  may  be  undertaken  at  the  same 
time,  the  residue  is  not  removed  from  the  dish  during  the  operation,  filtration  is 
