Am.  Jour.  Pharm.  \ 
March,  19 19.  * 
Melting  Point  of  Rosin. 
183 
than  those  present  in  the  crude  drug  having  been  developed  during 
the  process  of  drying. 
Research  Laboratory,  Parke,  Davis  &  Co., 
Detroit,  Mich. 
MELTING  POINT  OF  ROSIN.1 
By  T.  Linsey  Crossley. 
Centain  large  buyers  of  rosin  have  recently  specified  a  melting 
point  limit  for  this  material.  Samples  have  been  submitted  for  this 
test,  but  without  specifying  how  the  test  was  to  be  carried  out. 
Properly  speaking,  rosin,  like  asphalt,  has  no  definite  melting 
point,  therefore,  any  specification  aiming  to  grade  it  by  reference  to 
its  behavior  on  heating  should  state  the  method  for  obtaining  results. 
Schwalbe  and  Kuderlinn2  not  only  state  melting  points,  but  record 
results  to  fractions  of  one  degree  and  claim,  to  differentiate  between 
certain  rosins  by  their  melting  points. 
Several  methods  have  been  used  to  determine  the  quality  of  rosin 
as  indicated  by  its  action  on  heating.  The  closed  capillary  tube, 
of  such  general  application,  is  used  largely  but,  unless  .conditions  of 
heating  and  observation  are  closely  controlled,  results  are  not  uni- 
form with  different  operators. 
The  following  results  were  obtained  on  the  same  four  samples 
by  methods  indicated : 
Rosin. 
Yx"  Column. 
0  F> 
Yz"  Column, 
"°  F. 
Film,  of. 
Capillary, 
0  F. 
I  
174-184 
172-183 
176-I87 
174-185 
169-172 
169-172 
165-173 
174-182 
167-176 
150 
146 
147 
155 
156 
I204 
134 
126 
135 
133 
... 
146 
HS 
i543 
i54 
147 
i53 
128 
130 
138 
136 
2  
3  
161-167 
161-157 
i 49-i 5 1 
145-146 
4  •  
153-155 
147-155 
149-153 
145-147 
144-145 
1  Reprinted  from  the  Jour,  of  Indust.  and  Engr.  Chem.,  January,  1919. 
2  "  Rosin  Studies/'  /.  Soc.  Chem,  Ind.,  30,  1397. 
3  Heated  until  clear. 
4  Probably  mechanical  weakness  of  film. 
