COMPOSITION  OF  VEGETABLE  GUMS. 
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bases,  but  that  the  resulting  substances  do  not  always  present 
identical  properties. 
The  soluble  gums,  true  lime  compounds,  appear  then  to  be  de- 
rived from  several  gelatinous  principles,  and  constitute  several 
terms  of  the  same  organic  series. 
M.  Fremy  sums  up  the  results  of  his  investigations  as  fol- 
lows : — 
1.  Gum  arabic  is  not  an  immediate  neutral  principle  ;  it  must 
be  considered  as  a  combination  of  lime  with  a  very  feeble  acid, 
soluble  in  water,  and  named  gummic  acid, 
2.  This  acid  may  undergo  an  isomeric  modification  and  be- 
come insoluble,  either  by  the  action  of  heat  or  by  the  influence 
of  concentrated  sulphuric  acid.  It  is  then  named  meta gummic 
acid. 
3.  The  bases,  and  principally  lime,  transform  this  insoluble 
acid  into  gummate  of  lime,  which  presents  all  the  chemical 
characters  of  gum  arabic. 
4.  The  soluble  lime  compound  which  forms  ordinary  gum,  may 
also  undergo  by  heat  an  isomeric  modification,  first  shown  by 
M.  Ge'lis,  and  is  transformed  into  an  insoluble  compound,  which 
is  metagummate  of  lime.  This  insoluble  substance  is  rendered 
soluble  by  the  action  of  boiling  water,  or  under  the  influence  of 
vegetation.  It  exists  in  the  vegetable  organism ;  it  forms  the 
gelatinous  part  of  certain  gums,  as  that  of  the  cherry  ;  it  is 
found  in  the  ligneous  tissue,  and  in  the  fleshy  pericarp  of  several 
fruits.  Its  isomeric  modification  illustrates  the  formation  of 
soluble  gums. 
5.  There  exists  in  the  vegetable  organization  several  insolu- 
ble gelatinous  bodies,  which  by  their  transformations  produce 
different  gums.  Thus,  the  insoluble  part  of  gum  tragacanth, 
modified  by  the  action  of  alkalies,  gives  a  gum  which  must  not 
be  confounded  with  gum  arabic.  Reagents  establish  a  striking 
difference  between  these  bodies. 
6.  When  it  is  seen  with  what  facility  gum  and  its  derivatives 
may?  by  undergoing  an  isomeric  modification,  be  transformed 
into  insoluble  substances,  a  hope  arises  that  a  practical  applica- 
tion in  the  arts  may  result,  and  that  it  may  be  employed  like 
albumen  for  fixing  insoluble  colors. — London  Pharm.  Jour, 
April,  1860. 
