THE  MOST  CORRECT  METHODS  FOR  PREPARING  EXTRACTS.  235 
extractum  taraxaci,  spec.  grav.  1.380,  at  14°  C ;  3,  consistence 
of  extractum  radio,  glycyrrh.  which  is  obtained  by  evaporating  the 
liquid  to  the  spec.  grav.  1.090  at  14°  C,  pouring  it  into  a  tared 
evaporating  dish,  and  evaporating  it  now  to  just  one-fourth  of 
its  weight;  4,  dry  and  in  form  of  powder.  Many  extracts, 
like  extr.  hyoscyami,  are  hygroscopic  in  such  a  degree,  that 
they  cannot  be  kept  in  powder,  or  cannot  be  dried  at  so  low  a 
temperature  as  to  preclude  an  injurious  effect  of  the  heat;  they 
require  the  addition  of  an  indifferent  powder,  and  a  number  of 
experiments  have  convinced  the  authors  that  finely  powdered 
liquorice  root  is  preferable  to  any  other  substance.  The  ex- 
tracts to  be  dried,  when  evaporated  to  the  second  consistence, 
are  with  constant  agitation  heated  in  a  water  bath  to  60°  C. 
(140°  F.,)  until  they  cease  to  lose  weight;  one-fourth  of  their 
weight  of  water  or  one-eighth  of  alcohol  is  then  added  again, 
well  mixed  and  an  equal  weight  of  pulv.  radic.  liquir.  alcoholis. 
stirred  in,  and  the  whole  rapidly  evaporated  to  dryness  at  60° 
C;  2  grs.  of  this  contain  1  gr.  pure  extract.  For  pills  or 
powders  these  extracts  may  be  used  as  they  are ;  for  mixtures, 
straining  is  necessary  after  their  solution;  for  ointments  they 
are  dissolved  in  four  parts  of  water,  strained  and  evaporated  to 
two  parts  ;  repeated  trials  have  convinced  the  authors,  that  this 
manipulation  requires  no  more  time  than  the  cold  dissolving  of 
the  extracts  before  their  admixture  with  the  ointment.  The  fol- 
lowing extracts  can  be  kept  in  powder  without  any  addition  : 
Extr.  cascarillae,  chamomillae,  cinchonas  fuscae,  Colombo,  guaiaci, - 
juglandis,  millefolii,  quassiae,  ratanhae,  salviae,  tormentillae.  The 
following  require  the  addition  of  powdered  liquorice  root :  Extr. 
absinthii,  aconiti,  acori,  angelicae,  arnicae,  belladonnae,  cardui 
bened.,  centaurei  min.,  chelidonii,  cichorei,  conii,  digitalis,  dul- 
camarse,  filicis  maris,  gentianae,  haemostaticum,  (ergotae  Bonj.,) 
hyoscyami,  hellebori  nigri,  lactucae  virosae,  mezerei,  nucis  vomicae, 
saponariae,  sarsaparillae,  scillae,  trifolii  fibr.,  Valerianae. 
To  arrive  at  reliable  results,  the  authors  employed  the  same 
quantity  of  menstruum,  for  preparing  the  same  extract  by  the 
process  of  decoction,  infusion  or  percolation,  and  evaporated  all 
extracts  to  dryness,  the  only  reliable  standard  for  comparison. 
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