216  Oils  of  Fire  weed  and  Erigeron.  {AmMay,ri£3.arm* 
was  found  that  a  temperature  of  1500  C.  was  sufficient  to  remove  a 
greater  percentage  of  the  water  without  danger  of  converting  into 
the  manganoso-manganic  oxid.  The  precipitate  approximates  the 
following  composition:  4MnO.  20  to  25  Mn02. 
Manganese 
Total 
as        Total  Mn 
Temp,  of 
Manganese 
MnOo.  i 
is  Mn02. 
Water. 
o-5  Gm .  =■ 
Approximate 
Drying. 
Per  Ct. 
Per  Ct. 
Per  Ct. 
Per  Ct. 
MnS04  Gm. 
Composition. 
IOO°  C. 
6o*6o 
3578 
59*°5 
n-37 
0-8321 
4Mn0.6Mn02 
125°  C. 
61-35 
48-80 
79'56 
6-62 
0*8424 
4Mn0.i6Mn02 
150°  c. 
62-41 
54*6 1 
87-5I 
3-56 
0-8570 
4Mn0.25Mu02 
150°  c. 
6277 
52 -o6 
82-94 
3.84 
0*8620 
4Mn0.2oMn02 
In  view  of  the  suggestion  of  Freidheim  that  the  composition  of 
the  precipitate  more  nearly  approximates  Mn02  with  the  increase  in 
the  percentage  of  ammonium  salts  added,  various  trials  were  made 
in  which  10  grammes  (No.  I),  25  grammes  (No.  II),  and  50  grammes 
(No.  Ill)  of  ammonium  sulphate  were  employed,  using  the  same  pro- 
portions of  usual  reagents,  with  negative  results  as  far  as  the  com- 
position of  the  precipitate  is  concerned.  Freidheim  employed  much 
larger  quantities  of  the  ammonium  salt  than  we  did,  which  may 
explain  differences. 
Total  Mn. 
Mn  as 
Total  Mn 
Number. 
Dried  at 
Per  Cent. 
MnOo. 
as  Mn02. 
Water. 
I 
150°  c. 
62-74 
50-85 
8ro6 
4*22 
II 
150°  c. 
63-22 
49*63 
78-5I 
3  *95 
III 
1500  c. 
62'6o 
5I-26 
81*90 
4'30 
Inasmuch  as  we  are  able  to  obtain  a  product  of  fairly  constant  com- 
position, with  some  manganous  oxid  present,  which  is  to  its  advant- 
age, we  considered  further  experiments  in  this  direction  unnecessary. 
The  approximate  yield  in  oxid  from  50  grammes  of  manganese 
sulphate  is  20  grammes. 
ESSENTIAL  OILS  OF  FIREWEED  AND  ERIGERON. 
By  Lyman  F.  Kebler  and  Dr.  George  R.  Pancoast. 
Genuine  oil  of  fireweed,  Erechthitis  hieracifolia,  is  comparatively  a 
commercial  rarity.  The  chief  sources  of  supply  are  small  distillers, 
composed  principally  of  farmers,  whose  botanical  knowledge  is  not 
very  extensive.  The  plants  are  gathered  by  these  men  and  their 
help,  the  latter  frequently  caring  little  as  to  the  kind  of  "  weeds" 
collected,  and  when  it  is  remembered  that  the  common  name  "  fire- 
weed  "  is  applied  to  no  less  than  six  different  wild  plants,  it  is  not 
