460 
Standard  Sieves. 
Am.  Jour.  Phariru 
October,  1903. 
STANDARD  SIEVES.1 
By  Joseph  P.  Remington. 
For  many  years  it  has  been  the  custom  in  the  drug-milling  trade 
to  designate  the  fineness  of  powders  by  the  grade  of  the  sieve 
through  which  the  powder  is  sifted.  Our  Pharmacopoeia,  for  sev- 
eral revisions,  adopted  the  system  in  use  by  wire-cloth  manufac- 
turers, who  designate  the  grade  of  the  wire  cloth  by  the  number  of 
the  meshes  in  the  linear  inch. 
The  United  States  Pharmacopoeia  of  1890  directs  five  degrees  of 
fineness  of  powder,  as  follows  : 
A  very  fine  powder  should  pass  through  a  sieve  having  80  or 
more  meshes  to  the  linear  inch — No.  80  powder. 
A  fine  powder  should  pass  through  a  sieve  having  60  meshes  to 
the  linear  inch — No.  60  powder. 
A  moderately  fine  powder  should  pass  through  a  sieve  having  50 
meshes  to  the  linear  inch — No.  50  powder. 
A  moderately  coarse  powder  should  pass  through  a  sieve  having 
40  meshes  to  the  linear  inch — No.  40  powder. 
A  coarse  powder  should  pass  through  a  sieve  having  20  meshes 
to  the  linear  inch — No.  20  powder. 
In  conducting  experiments  upon  fluid  extracts  for  the  Revision 
Committee,  the  writer  was  struck  with  the  difference  in  the  appear- 
ance of  powders  sold  by  different  manufacturers,  labeled  No.  30 
powder.  The  difference  was  easily  perceptible  to  the  naked  eye, 
and  an  investigation  and  correspondence  with  the  various  manufac- 
turers of  wire  cloth  in  the  United  States  revealed  the  cause  of  the 
discrepancy.  These  manufacturers  cheerfully  responded  to  in- 
quiries, and  were  of  much  assistance  to  the  writer. 
The  thickness  of  the  wire  used  in  making  the  sieve-cloth  should 
always  be  specified,  if  uniform  results  are  to  be  obtained.  When 
our  Pharmacopoeia  designates  a  No.  20  powder,  it  should  state,  in 
addition  to  the  directions,  that  the  sieve  should  contain  20  meshes 
in  each  linear  inch ;  that  the  wire  should  be  gauge  No.  28,  and,  of 
course,  the  gauge  of  the  wire  should  be  given  for  each  degree  of 
fineness  of  the  wire-cloth.  According  to  standard  gauges  adopted 
by  the  Wire  Cloth  Manufacturers'  Association,  March,  1899,  the 
1  Read  at  the  annual  meeting  of  the  Pennsylvania  Pharmaceutical  Associa- 
tion, June,  1903. 
