94 
North  American  Conifer ce. 
( Am.  Jour.  Pharm. 
t  February,  1897. 
It  will  be  seen  from  this  analysis  of  the  bark  that  the  important 
constituents  are  tannin,  resin  and  hemlock  red;  all  of  these  con- 
stituents  vary  with  the  season  of  the  year.  Hemlock  red  may  be 
an  intermediate  product  between  the  resins  and  the  tannin ;  its  pro- 
portion in  the  bark  is  very  variable. 
HEMLOCK  TANNIN. 
The  tannin  of  hemlock  bark  has  received  so  little  attention  at 
the  hands  of  investigators,  and  is  of  so  much  importance  industrially, 
that  it  is  considered  worthy  of  especial  notice  here. 
Occurrence. — The  few  results  that  have  been  published  concern- 
ing the  amount  of  tannin  in  hemlock  bark  are  widely  at  variance 
with  one  another.  Procter1  says  it  contains  nearly  14  per  cent.;  he 
probably  quoted  Mulligan  and  Dowling,2  who,  in  1859,  found  13-9 
per  cent.  Mafat,3  1892,  gives  8  to  10  per  cent,  as  the  average 
amount.  The  following  results  will  show  that  there  may  be  a  great 
variation  in  the  proportion  present,  according  to  the  season  of  the 
year  and  other  circumstances: 
PERCENTAGES  OF  MOISTURE,  ASH  AND  TANNIN  IN  THE  BARK  OF  TSUGA  CANADENSIS. 
Date  of 
Collection. 
Moisture. 
Ash  in 
Absolutely 
Dry  Bark' 
Tannin  in 
Absolutely 
Dry  Barkr 
Remarks. 
May  12,  1S95   .  .  . 
2o-o6 
1-46 
S-22 
Small  tree. 
Near  Philadelphia. 
June  30,  1895  .  .  . 
I5-54 
3"°3 
9-82 
Taken  from  a  branch. 
August  1,  18951  .  . 
IO'OO 
2-51 
H77 
Small  tree.    Bark  from  trunk. 
October  27,  1895  . 
1 1*90 
1*21 
I5'I2 
November  28,  1895 
14*01 
i*43 
15*45 
Medium"         "      "  " 
January  17,  1897  . 
I3'45 
1*58 
I3"°5 
May,  1896  .... 
1073 
1-56 
io'6o 
I,arge    "         "  " 
Tennessee. 
June,  1896  .... 
10-43 
1 '40 
14-96 
July,  1896  .... 
10-98 
1-29 
n-34 
1  This  sample  was  taken  from  the  same  tree  that  yielded  the  root  bark,  the  composition  of  which  has 
been  given  on  a  previous  page  of  this  article. 
Hemlock  bark  is  usually  collected  during  the  months  of  May, 
June  and  July,  and  the  three  samples  in  the  foregoing  table  which 
1  Text-Book  of  Tanning,  p.  31. 
2  Chemical  Gazette,  17,  430. 
3  Bulletin  de  la  Societe  industrielle  de  Mulhouse,  63,  130.  Am.  Jour. 
Pharm.,  64, 531. 
