Am.  Jour.  Pharm.  \ 
February,  1895.  J 
Iodides  of  Tin. 
*3 
Fig.  2. — Small  portion  of  cross-section  of  same  rhizome  more  highly  magni- 
fied, showing  portions  of  cortex,  cylinder-sheath  and  central  cylinder,  a,  in 
tercellular  space  in  cortex  ;  b,  cylinder-sheath;  c,  xylem  of  one  of  the  bundles 
in  exterior  portion  of  central  cylinder.    Magnification,  100  diameters. 
Fig.  j. — Crystals  of  calcium  oxalate  from  rhizome.  Magnification,  150 
diameters. 
Fig.  4.. — A  few  parenchyma  cells  from  central  cylinder  of  rhizome,  showing 
granules  similar  in  appearance  to  starch  grains.    Magnification,  495  diameters. 
Fig.  5. — Portion  of  cross-section  of  root  of  Iris  versicolor,  magnified  100 
diameters,  a,  epidermis  ;  b,  cell  of  cortical  parenchyma  ;  c,  large  duct  in 
vasal-bundle  ;  d,  endodermal  cell ;  e,  pericambium  cell ;  f,  small  ducts  at 
exterior  end  of  xylem  ray. 
IODIDES  OF  TIN._ 
By  Charges  Buttock. 
Iodide  of  tin  has  been  called  for  recently  in  medical  practice  for 
its  supposed  benefit  in  some  forms  of  pulmonary  disease. 
Tin  forms  with  iodine  two  compounds — stannous  iodide,  Snl2  and 
stannic  iodide,  Snl4.  Stannous  Iodide  is  formed  when  iodide  of 
potassium  is  added  in  slight  excess  to  a  solution  of  stannous  chloride. 
The  solution  must  be  made  free  from  excess  of  acid  by  long  diges- 
tion at  a  moderate  heat  in  a  flask  over  mossy  tin. 
The  iodide  is  precipitated  as  a  yellow-red  powder,  somewhat 
gelatinous  in  character.  When  thrown  upon  a  filter  the  filtrate  is 
quite  acid,  and  the  iodide  when  washed  soon  turns  white  by  decom- 
position, forming  oxide  of  tin  and  hydriodic  acid.  If  heated  in  a 
flat  porcelain  dish  without  washing  it  evolves  hydriodic  acid  and 
changes  to  a  brown-red  powder.  The  best  method  was  found  to 
be  the  drying  of  the  precipitate  immediately  between  folds  of  bibu- 
lous paper.    In  this  condition  it  still  remains  acid  when  dry. 
Stannous  iodide  crystallizes  in  yellowish-red  needles ;  it  dissolves 
slightly  in  water  and  soon  decomposes  with  formation  of  hydriodic 
acid  and  oxide  of  tin.  In  warm  solution  of  the  chlorides  and 
iodides  of  the  alkali  metals  it  dissolves  freely.  When  heated  to 
near  redness  in  the  absence  of  air  it  liquefies,  but  does  not  sublime  ; 
on  cooling,  it  solidifies  into  a  crystalline  mass,  which  affords  a 
yellow-red  powder.  When  heated  in  an  open  vessel  it  is  resolved 
into  stannic  iodide,  which  sublimes,  and  oxide  of  tin  is  left. 
Stannic  Iodide,  Snl4  (tetra  iodide)  is  obtained  when  tin  and 
iodine  are  brought  together  in  a  dry  state.  To  prepare  it,  tin  in  a 
granular  condition  is  placed  in  a  flask,  and  twice  its  weight  of 
