432  PROPERTIES  OF  SILICATES.     NEW  ANTIDOTES. 
have  just  examined  a  favorable  specimen,  which  is  probably  still 
unsold.  This  contains  some  better  bark  of  the  trunk  mixed 
with  a  preponderance  of  that  of  the  root.  Separating  this 
last,  I  found  that  it  would  be  worth  about  half  the  price  of  flat 
Calisaya. 
This  question  ought  certainly  to  be  set  at  rest,  as  it  easily 
might  be  by  the  sacrifice  of  some  half-dozen  trees  out  of  the 
million  plants  of  the  Cinchona  Pahudiana  which  the  Dutch 
possess  in  the  island  of  Java.  If,  from  the  root-bark  of  these 
a  competent  proportion  of  commercial  sulphate  of  quinine  can 
be  obtained  to  defray  the  expense  of  cultivation,  then  the .  im- 
portant fact  of  their  value  will  be  established  ;  but  I  believe 
this  has  not  yet  been  done. 
In  time  for  the  next  number  I  hope  to  send  a  paper  on  the 
so-called  "bark  from  the  root  of  0.  lancifolia"  which  is  really 
a  very  interesting  new  variety  of  the  O.  Pitayensis — the  Pitaya 
roja  of  commerce. — London  Pharm.  Joum.,  July  1,  1864. 
PROPERTIES  OF  SILICATES. — NEW  ANTIDOTES. 
To  the  Editor  of  the  Chemical  News. 
Sir, — Gelatinous  silica  being  known  to  be  soluble  in  alka- 
line solutions  such  as  those  of  caustic  soda,  it  might  fairly  be 
presumed  that  it  would  also  be  soluble  in  an  alkaline  silicate, 
although  I  am  not  aware  «of  this  having  been  published  as 
a  fact. 
But  the  same  property  could  not  probably  have  been  antici- 
pated of  the  silicates  of  the  earth  and  metals.  The  silicate  of 
magnesia,  for  example,  in  the  gelatinous  or  recently  prepared 
state,  is  not  soluble  in  a  solution  of  caustic  soda,  but  readily  so 
in  a  solution  of  silicate  of  soda  ;  and  the  latter  rule  holds  good 
through  all  the  series  of  silicates. 
The  solvent  power  of  the  alkaline  silicates  seems,  therefore, 
to  be  altogether  different  in  degree  and  in  other  important  par- 
ticulars from  that  of  other  alkaline  solutions.  Hence  through 
this  property  we  have  soluble  glass  in  as  great  variety  and  of 
tints  as  various  and  delicate  as  we  have  in  stained  glass.  The 
soda  silicate  of  cobalt  is  of  a  beautiful  rose  color — that  of 
chromium  green,  &c.    But  the  tints  of  the  metallic-colored 
