Am.  Jour.  Pharm. ) 
Jan.,  1883.  J 
Note  on  Asbestos  Filters. 
37 
-crystals  obtained,  which  obstinately  retain  the  syrup  between  their 
laiminsB,  so  that  it  is  almost  impossible  to  work  with  concentrated  solu- 
tions. If,  however,  as  it  is  stated  by  the  author,  the  crystals  he  obtains 
are  in  the  form  of  prisms,  and  of  comparatively  large  size,  the  centrifu- 
gal process  could  be  used  with  highly  concentrated  solutions.  It  may 
be  stated  that  the  relative  sweetening  power  of  anhydrous  glucose,  as 
compared  with  that  of  cane  sugar,  is  as  three  to  five ;  in  other  words, 
in  order  to  use  glucose  with  economy,  it  should  be  bought  for  less  than 
^three-fifths  of  the  cost  of  crystallized  cane  sugar. — Editor  of  the  Chem- 
ists^ Journal. 
NOTE  ON  ASBESTOS  FILTERS. 
By  p.  Cassamajor. 
An  extensive  dealer  in  wares  used  by  chemists  lately  informed  me 
that  he  had  many  inquiries  concerning  asbestos  for  filtering  liquids  in 
chemical  analysis.  Some  chemists  complain  that  they  connot  get  clear 
solutions  through  asbestos,  while  others,  who  obtain  clear  solutions, 
find  that  their  liquids  filter  altogether  too  slowly. 
Allow  me  to  recall  that  the  method  of  making  asbestos  filters  by 
pouring  a  thin  paste  of  this  material  over  a  perforated  platinum  disc 
was  first  proposed  by  me  in  1875,^  but  I  neglected  to  give  directions 
concerning  the  preparation  of  asbestos,  to  make  it  fit  for  filtering 
liquids  in  chemical  analysis.  It  now  appears,  however,  that  such 
"directions  would  be  found  useful,  and  I  propose  to  repair  the  omission 
and  give  the  necessary  details. 
The  kind  of  asbestos  to  use  is  a  matter  of  some  importance.  I  have 
tried  three  kinds,  which  are  sold  by  dealers  in  New  York,  as  the 
Canadian,  the  Italian  and  the  Australian.  This  last  is  less  flexible 
than  the  other  two,  and  consequently  the  fibres  do  not  felt  together 
^  and  pack  as  closely  on  the  perforated  plate.  Hence  liquids  filter  more 
rapidly,  and  the  Australian  is,  on  this  account,  preferable  to  the  two 
other  kinds.  I  am  informed  that  the  Canadian  asbestos  is  the  most 
soluble  in  acids,  but  I  have  not  verified  the  assertion. 
Whatever  may  be  the  kind  of  asbestos  used,  the  following  is  a  pro- 
.  cess  for  obtaining,  with  little  trouble,  a  quantity  of  the  pulp  in  a  fit 
state  for  filtration : 
A  coarse  brass  sieve  is  placed  over  a  sheet  of  paper,  and  a  handful 
^  See  "American  Chemist,"  v,  p.  44.    "  Chemical  News,"  xxxii,  p.  46, 
