440 
A  Ikaloidal  Periodides. 
J  Am.  Jour.  Pharm. 
I  September,  1898. 
vegetable  alkaloids  agree  in  general  with  the  perhalides  of  pyridine 
and  its  more  immediate  derivatives,  as  these  have  been  previously 
studied  in  the  same  laboratory.  Also  the  reactions  of  these  perio- 
dides  of  the  bases  of  the  pyridine  type  are  generally  the  same  as 
those  of  caffeine  pentiodide,  formed  when  caffeine  is  in  acidulated 
solution,  as  found  by  Gomberg.  And  these  bodies  are  to  be  studied 
with  perhalides  in  general,  and  with  the  question  of  the  orders  of 
'  bases  capable  of  forming  perhalides,  and  the  relation  of  these,  in 
structure,  to  the  double  halides.  The  production  of  a  periodide  of 
bromtriphenylmethane,  about  to  be  published  by  Gomberg,  is  of 
interest  as  an  organic  perhalide,  destitute  of  any  element  of  the 
nitrogen  family,  as  was  also  the  iodonium  perhalide  obtained  by 
Victor  Mayer,  in  1894,  and  the  sulphon  periodide  reported  in  this 
country  by  Kastle  in  the  same  year. 
The  higher  periodides  of  the  vegetable  alkaloids,  as  named  above, 
are  sufficiently  stable  to  give  very  constant  results  in  the  analysis, 
both  for  the  additive  iodine  and  for  that  of  the  hydriodide.  Obtained 
in  crystalline  forms  they  were  found  to  have  the  same  composition 
as  the  amorphous  precipitates  after  washing  and  drying.  In  the 
volumetric  procedure,  however,  washing  is  avoided,  an  aliquot  por- 
tion of  the  filtrate  being  taken  in  which  to  titrate  back  with  the 
thiosulphate  for  the  excess  of  iodine  added.  In  this  way  is  obtained 
a  very  accurate  measure  of  the  iodine  consumed  in  supplying  the 
additive  iodine  of  the  periodide.  The  more  firmly  bound  iodine  of 
the  alkaloidal  hydriodides,  not  responding  to  reducing  agents,  is 
supplied  by  the  iodine  of  the  potassium  iodide,  that  of  Wagner's 
reagent,  or  iodo-potassium  iodide,  always  employed.  This  probable 
explanation  of  the  reaction  of  the  precipitation  was  verified  by  the 
authors  in  a  quantitative  investigation  at  some  length. 
The  results  of  analysis  of  the  periodides  were  found  to  be  well 
sustained  by  constant  results  in  volumetric  estimation,  the  alkaloid 
to  iodine  factors  calculated  from  the  chemical  formulae  of  the  perio- 
dides being  used  in  every  case  for  the  volumetric  work,  with  agree- 
ment quite  satisfactory,  as  presented  below.  The  calculation  for 
each  alkaloid  was  made  upon  its  chemical  formula,  as  given  in  a 
previous  paragraph : 
