AmjJner'i9ih9rm"  )        Zinc  and,  Copper  in  Gelatin.  383 
and  it  appears  to  be  almost  undisturbed  by  the  boiling  of  the  solvent. 
If  the  boiling  be  stopped,  and  the  plastic  mass  be  separated  into  par- 
ticles with  a  glass  rod,  it  only  requires  a  gentle  rotation  of  the  flask 
to  bring  the  wet  powder  to  an  almost  immobile  mud  again.  Subse- 
quent extractions  with  fresh  quantities  of  the  boiling  solvent  do 
little  to  granulate  the  mud.  and  after  as  many  as  twelve  or  fourteen 
percolations  the  mass  is  not  completely  exhausted  of  alkaloids. 
It  is  better  to  reduce  the  amount  of  water ;  approximately  12  Cc. 
of  this  gives,  with  10  Gm.  of  powdered  bark  and  6  Gm.  of  calcium 
hydroxide,  a  powder  of  the  right  consistency.  Using  this  proportion 
of  water,  higher  contents  of  total  alkaloids  were  obtained  on  three 
occasions,  the  increases  being  respectively  2.02,  1.16  and  146  per 
cent,  above  the  amounts  found  when  the  pharmacopceial  instructions 
were  followed.    All  the  same,  the  process  remains  very  tedious. 
That  the  Pharmacopceial  Revision  Committees  have  retained 
Squibb's  process  (with  different  modifications)  through  the  1885, 
1898  and  1914  editions,  seems  to  imply  a  special  confidence  in  it ; 
but  as  at  present  described  I,  at  any  rate,  have  not  been  able  to  ob- 
tain satisfactory  results  with  it. 
30,  Great  James  Streets, 
Bedford  Row,  W.C.I.,  Loxdox. 
THE  DETERMINATION  OF  ZIXC  AXD  COPPER  IX 
GELATIN.1 
By  George  S.  Jamiesox. 
One  method  used  for  the  determination  of  zinc  and  copper  in 
gelatin  is  based  upon  the  complete  destruction  of  the  organic  matter 
by  digestion  with  nitric  and  sulphuric  acids.2  After  the  digestion 
is  completed,  water  is  added,  and  the  solution  is  made  slightly  alka- 
line with  ammonium  hydroxide.  Then  a  measured  quantity  of 
hydrochloric  acid  is  added.  The  copper  is  precipitated  as  sulphide 
and  filtered.  The  filter  containing  the  copper  sulphide  is  digested 
with  nitric  and  sulphuric  acids  until  a  colorless  solution  is  obtained. 
The  copper  is  finally  titrated  by  the  well-known  iodide  and  thiosul- 
phate  method.    W  nen  the  hydrogen  sulphide  has  been  removed 
1  Reprinted  from  Jour,  of  Iud.  and  Engr.  Chcm.,  April,  1919.  Published 
by  permission  of  the  Secretary  of  Agriculture. 
2Met'hods  of  analysis,  A.  O.  A.  C.,  1916,  175. 
