6io 
The  Acid  of  Willow  Bark. 
Am.  Jour.  Pharm. 
Doc,  1877, 
tate  is  then  separated  by  filtration,  the  filtrate  concentrated  and 
extracted  with  ether,  which  dissolves  the  acid.  The  ether  being  now 
driven  off,  a  syrupy  solution  of  the  acid  is  left.  A  few  ounces  were 
prepared  by  this  method  and  placed  over  sulphuric  acid,  under  a  bell- 
glass,  for  two  days.  The  acid  then  remained  in  the  form  of  a  syrup, 
almost  odorless,  with  an  intensely  sour  taste.  As  in  these  respects  it 
exactly  resembled  lactic  acid,  and  seeing  that  the  calcium  salt  in  its 
crystalline  form  and  in  its  percentages  of  H20  and  Ca  corresponded  with 
calcic  di-lactate,  there  could  be  little  doubt  that  the  acid  under  exami- 
nation was  lactic  acid.  To  make  more  certain,  however,  some  further 
tests  were  applied.  A  little  was  heated  in  a  test-tube,  when  water  and 
carbonic  anhydrid  were  given  off,  and  a  residue  left  which  shortly 
solidified.  A  portion  was  then  boiled  with  sulphuric  acid,  which  liber- 
ated an  inflammable  gas,  burning  with  a  blue  flame — no  doubt,  carbon 
monoxide.  When  a  small  quantity  was  heated  with  sulphuric  acid  and 
manganese  dioxide,  a  vapor  smelling  like  aldehyd  was  evolved.  A 
portion  of  the  acid  was  distilled  and  the  fraction  coming  over  above 
I30°C.  was  evaporated  and  treated  with  cold  alcohol,  which  separated 
small  white  crystals  having  the  form  of  rhomboidal  plates,  and  in  other 
respects  resembling  lactide. 
From  the  acid  as  above  obtained  the  zinc-salt  was  prepared  by  warm- 
ing with  excess  of  zinc  carbonate,  filtering,  and  allowing  to  crystal- 
lize. The  crystals  were  pressed  between  blotting  paper  and  exposed 
for  a  short  time  to  the  air.  In  these  air-dried  crystals  the  H20  was 
determined  by  drying  in  the  water-bath  ;  6*065  grs«  l°st  I<125  grs«= 
18*46  per  cent.  In  a  second  determination  with  another  crop  of  crys- 
tals 9*275  grs.  lost  1*695  grs. =18*27  Per  cent«  The  zinc  was  deter- 
mined in  the  dry  salt  by  ignition  in  the  blow-pipe  flame  ;  6*33  grs.  gave 
2*12  grs.  ZnO=33*49  per  cent.  In  another  determination  7*58  grs. 
gave  2*55  grs.  ZnO=33*64  per  cent. 
The  above  numbers  are  here  compared  with  those  calculated  for  the 
normal  calcium  and  zinc  salts  of  latic  acid  respectively  : 
Ca(C3H503)2>5H20. 
Ca  .    .  . 
Zn(C3H503)2,3  H20 
H20 
ZnO 
Found. 
per  cent. 
II. 
mean. 
29*22 
30-03 
28-98 
29-505 
18-34 
18-34 
18-35 
18*345 
Found. 
per  cent. 
I. 
II. 
mean. 
18  33 
18-46 
18-27 
18-36 
3338 
3  3  "49 
33^4 
3356 
