242  EXAMINATION  OE  SOME  OF  THE  RESINS  AND  GUM  RESINS. 
The  composition  of  the  potassa  salt  is, 
Cm'0\  KO  HO  +  HO. 
98  parts  of  cantharidin  gives  163  parts  of  cantharidate  of  po- 
tassa.   Boiling  water  dissolves  8-87  per  cent.  ;  cold  water  4-13  ; 
boiling  alcohol  0*92  ;  cold  alcohol  0*03  per  cent.    It  is  also  in- 
soluble in  ether  and  chloroform. 
The  author  proposes  the  following  formula  for  a  blistering 
tissue,  after  numerous  experiments  : 
Take  of  Gelatin,  30  grains, 
Water,  150  " 
Alcohol,  150  " 
Cantharidate  of  Potassa,  6  " 
Glycerin,  a  sufficient  quantity. 
This  liquid  is  spread  uniformly  with  a  brush  on  gutta  percba 
in  thin  sheets,  so  that  each  square  of  four  inches  will  contain  one 
centigramme  (about  one-seventh  of  a  grain)  of  the  cantharidate 
of  potassa.  The  strength  may  be  varied  at  will. — Jour,  de  Chim. 
Med.  lilars,  1870. 
EXAMINATION  OF  SOME  OF  THE  RESINS  AND  GUM  RESINS. 
By  Dr.  Sace  (of  Switzerland.) 
(Translated  from  the  German  by  Chas.  Caspari,  Jr.) 
The  author  states  that,  having  observed  a  great  analogy  be- 
tween these  substances,  he  was  induced  to  test  their  chemical 
reactions,  in  order  to  ascertain  something  more  definite  about 
them.  The  following  substances  were  used  by  him,  in  fine  pow- 
der, in  his  experiments,  viz.  :  Gum  copal,  amber,  dammar, 
shellac,  elemi,  sandrach,  mastiche  and  rosin.  The  solvents, 
given  below,  were  used  in  the  quantity  of  thrice  the  bulk  of 
gum,  and  allowed  to  act  upon  the  same  for  24  hours,  at  a  tem- 
perature of  59—72°  Fahr. 
In  boiling  water  resin  changes  to  a  semiliquid  mass  ;  dammar, 
shellac,  elemi  and  mastiche  cake,  and  copal,  amber  and  sandrach 
are  not  affected  at  all.  In  alcohol,  dammar  and  amber  are  in- 
soluble; copal  cakes;  elemi  is  with  difficulty  soluble;  rosin,  shel- 
lac, sandrach  and  mastiche  dissolve  very  readily.  In  ether,  amber 
and  shellac  are  insoluble  ;  copal  swells ;  rosin,  elemi,  sandrach 
and  mastiche  dissolve  readily. 
