332 
Alkaloidal  Color  Tests. 
Am.  Jour.  Pharm. 
July,  1903. 
alkali,  and  the  liberated  alkaloid  removed  by  ether  as  in  Stas'  proc- 
ess. It  must  be  borne  in  mind,  however,  that  in  treating  the  acidu- 
lated solution  with  ether,  certain  alkaloidal  bodies,  as  well  as  color- 
ing matter  and  other  associated  impurities,  may  be  removed.  This 
is  especially  true  of  the  weaker  bases,  such  as  berberine,  hydrastine, 
colchicine,  etc. 
The  second  difficulty  was  overcome  by  the  introduction  of  chloro- 
form1 and  amylic  alcohol.2  Chloroform  and  ether  are  usually  em. 
ployed  because  they  volatilize  readily  at  low  temperatures,  and  most 
alkaloids  are  sufficiently  soluble,  for  most  work,  in  either  one  or  the 
other  or  mixtures  of  the  two.  Amylic  alcohol  is  usually  employed 
only  tor  morphine,  which  is  quite  insoluble  in  the  above  solvents. 
The  third  point  has  never  received  much  attention,  consequently 
our  knowledge  along  this  line  is  very  fragmentary.  There  are 
many  cases  where  a  substance  is  insoluble  or  sparingly  soluble  in  a 
given  solvent,  but  the  presence  of  a  third  body  makes  it  freely  solu- 
ble. For  example,  iodine,  sparingly  soluble  in  water,  is  rendered 
freely  soluble  in  the  presence  of  potassium  iodide  or  certain  other 
alkaline  halogen  compound^.  Some  of  the  metallic  cyanides  are 
insoluble  in  water,  but  these  are  rendered  freely  soluble  by  the  pres- 
ence of  an.  alkaline  cyanide  like  potassium  cyanide.  Bismuth  citrate 
is  insoluble  in  water,  but  is  freely  soluble  in  this  menstruum  con- 
taining alkaline  citrates.  Pure  water  dissolves  only  traces  of  the 
essential  oils,  whereas,  concentrated  aqueous  saccharine  and  sodium 
salicylate  solutions  have  the  power  of  dissolving  considerable  quanti- 
ties of  these  oils.  Castor  oil  is  practically  insoluble  in  petroleum 
ether,  but  this  characteristic  insolubility  is  lost  at  the  ordinary 
temperature,  when  castor  oil  is  mixed  with  an  oil  soluble  in  the 
above  solvent,  like  croton  oil. 
G.  Dragendorff3  introduced  a  most  comprehensive  scheme,  which 
includes  all  of  the  good  points  of  his  predecessors'  methods,  by 
not  only  increasing  the  number  of  immiscible  solvents  employed, 
but  also  including  glucosides,  other  indifferent  plant  principles,  and 
some  synthetic  remedies.  Ingenious  and  comprehensive  as  is  this 
scheme,  yet  very  few,  if  any,  of  the  many  organic  bodies  it  is 
1 1856,  J.  E).  D.  Rodgers  and  G.  P.  Girwood,  Lancet,  June,  718;  Pharm.  J. 
Trans.,  16,  497. 
2i86i,  h.  Uslar  and  J.  Erdmann,  Ann.  (Liebig),  120,  121. 
3  1867,  Pharm.  Ztschr.f.  Puss.,  6,  663;  Ztschr.  anal.  Chetn.,  7,  521. 
