jo  Chemistry  of  Alkaloid  Estimations.     { A£eb™£y,m8m' 
ing  alkaloids  from  other  bodies  and  not  as  a  means  of  directly 
estimating  them. 
As  reagents  which  have  been  used  for  the  precipitation  of  certain 
alkaloids  the  following  may  be  mentioned :  It  has  been  proposed 
to  precipitate  quinine  by  means  of  ammonium  sulphocyanide  in 
presence  of  a  zinc  salt  and  the  precipitate  under  definite  conditions 
is  claimed  to  have  a  constant  composition— viz.,  4  molecules  of 
quinine,  -f-  3  molecules  zinc  sulphocyanide,  -f-  2  molecules  ammo- 
nium sulphocyanide,  -f-  4  molecules  hydrogen  sulphocyanide. 
While  quinine  oxalate  is  insoluble  in  ether,  the  remaining  oxalates 
of  the  cinchona  alkaloids  are  soluble  in  ether.  It  is  therefore  pro- 
posed to  obtain  an  etheral  solution  of  the  cinchona  alkaloids  and  to 
determine  by  titration  with  the  standard  etheral  solution  of  oxalic 
acid  the  amount  of  total  alkaloids  contained  in  the  drug  and  to 
collect  and  weigh  the  insoluble  quinine  oxalate. 
The  Solubility  of  Alkaloids  in  Immiscible  Solvents  and  the  Hydrol- 
ysis of  Alkaloid  Salts. — At  the  present  time  nearly  all  estimations 
of  alkaloids  in  vegetable  drugs  and  their  preparations  are  based 
upon  two  properties  of  alkaloids — viz.,  free  alkaloids  are  generally 
insoluble  in  water  but  soluble  in  chloroform,  ether  and  similar  sol- 
vents, while  the  alkaloid  salts  are  soluble  in  water  but  insoluble  in 
ether,  chloroform,  etc.  To  this  general  ruling  a  few  exceptions  have 
been  generally  recognized.  Thus,  it  is  well  known  that  caffeine  and 
colchicine  can  be  extracted  from  acid  solutions  by  means  of  chloro- 
form. It  is  generally  said  that  these  alkaloids  are  too  weak  to  form 
salts,  although  a  more  correct  explanation  would  be  to  say  that, 
wfrile  these  alkaloids  do  form  well  defined  salts,  these  compounds 
are  decomposed  by  water  (hydrolyzed)  to  such  an  extent  that  the 
free  alkaloid  may  be  extracted  from  acid  solution  by  means  of  ether 
or  chloroform.  Just  as  we  have  inorganic  salts  that  are  very 
largely,  very  slightly  or  practically  not  at  all  decomposed  by  water 
(hydrolyzed),  so  with  alkaloids,  all  gradations  of  hydrolysis  are 
known.  This  has  been  studied  quite  extensively  within  recent 
years,  especially  by  C.  Kippenberger  and  Professor  Edward  Schaer, 
of  the  University  of  Strasburg,  and  his  students.  These  experi- 
ments have  shown  that  in  the  presence  of  a  considerable  excess  of 
the  strong  acids  the  hydrolysis  of  most  alkaloid  salts  is  slight  so 
that  no  alkaloid  is  extracted  when  such  a  solution  is  shaken  with 
chloroform  or  ether.    When  weak  acids  are  used,  such  as  phosphoric 
