PHYSICAL  CHARACTERISTICS  OF  OFFICINAL  POWDERS.  207 
processes  of  contusion  and  grinding  as  ordinarily  accomplished. 
After  obtaining  the  "coarse  powder,"  U.  S.  P.,  passed  through 
the  No.  20  sieve,  the  proportion  of  the  several  other  grades  con- 
tained in  it  was  ascertained  by  successive  siftings ;  in  each  case 
the  No.  40,  No.  50,  No.  60  and  No.  80  sieves  being  successively 
used.  The  powder  passing  through  No.  40  is  the  officinal  mod- 
erately coarse,  though  containing  Nos.  50,  60  and  80  powder  ; 
that  passing  through  No.  50  is  moderately  fine,  though  contain- 
ing No.  60  and  80  ;  that  passing  through  No.  60,  though  fine 
U.  S.  P.,  contains  also  the  very  fine,  which  is  not  separated  until 
the  No.  80  sieve  is  used. 
The  results  are  here  tabulated,  in  the  instances  of  gentian 
and  wild  cherry  the  average  of  several  operations  being  given  ; 
in  the  others,  carefully  noted  results  of  one  trial: 
Table  showing  the  percentage  of  Powders  of  the  several  officinal 
grades  in  specimens  of  u Coarse"  (No.  20)  Poivder,  TJ.  S.  P. 
No.  20. 
No.  40. 
No.  50. 
No.  60. 
No.  80. 
Loss. 
Average. 
Average. 
Average. 
Average. 
Average. 
Average. 
Gentian  Root. 
58-0 
7-7 
5-7 
101 
14.3 
4-2 
44-9 
12-8 
7-1 
12-2 
20-5 
2-5 
48-0 
13-3 
9-7 
10-2 
15-3 
3-5 
Wild  Cherry  Bark. 
54-4 
11-2 
9-0 
11-0 
12-9 
1.5 
43-5 
8-7 
9-6 
12-9 
22-6 
3-7 
Ginger  Root  (decorticated.) 
46-5 
26-5 
9-8 
2-8 
1-5 
12-9 
49-0 
20-5 
13-5 
5-0 
2-0 
10-0 
Ergot. 
81-0 
5-8 
4-1 
2-0 
2-5 
4-6 
72-1 
7-6 
6-1 
3-8 
4-0 
6-4 
Calisaya  Bark. 
37-0 
25-0 
9-1 
6-5 
21-0 
1-3 
17-0 
15-0 
16-0 
14-6 
33-3 
4-1 
It  will  be  seen  that  the  greatest  difference  in  results  between 
grinding  aud  contusion,  in  the  above,  is  in  the  case  of  Peruvian 
bark,  the  short  fibres  of  which,  subjected  to  grinding,  most 
readily  pass  into  coarse  powders,  whilst  contusion  produces  a 
