274  Gleanings  from  the  European  Journals.  {AMjuneRi. 
Pharm. 
1874. 
1st.  The  author  calls  attention  to  the  fact  that  the  optical  behavior 
is  no  reliable  criterion  for  the  purity  of  volatile  oils,  the  rotatory  power 
of  their  proximate  constituents  being  influenced  and  often  reversed 
by  various  agents.  Even  the  color  reactions  are  more  or  less  depen- 
dent upon  the  relative  proportion  of  these  compounds ;  but  some  are 
so  characteristic  that  they  deserve  attention.  Thus  oil  of  peppermint 
is  colored  beautifully  green  or  blue  by  a  very  small  quantity  of  nitric 
acid,  and  it  acquires  at  the  same  time  a  fluorescence,  appearing  cop- 
per-red by  reflected  light.* 
The  influence  of  chloral  upon  oil  of  peppermint  has  been  noticed 
by  Jehn.f  The  author  found  that  his  samples  of  the  oil  were  colored 
but  slightly  brown  or  yellow  by  chloral  hydrate,  even  after  the  appli- 
cation of  heat ;  but  anhydrous  chloral  alters  the  oil  gradually  at  ordi- 
nary temperature.  Of  two  samples  which  showed  exactly  the  same 
behavior  to  nitric  acid,  one  acquired,  with  one-fifth  volume  of  anhy- 
drous chloral,  gradually  a  brown  color,  while  the  other  turned  greeny 
the  color  being  always  purer  and  richer  after  a  contact  of  some  hours 
or  days  in  the  cold. 
Concentrated  sulphuric  acid  or  bromine  also  show  peculiar  colora- 
tions ;  the  reaction  should  be  moderated  by  the  addition  of  carbon 
bisulphide.  Very  remarkable  differences  are  observed  on  agitating 
different  samples  of  the  oil  with  a  saturated  solution  of  bisulphite  of 
sodium ;  one  was  colored  green,  then  blue ;  the  other  rose-red,  violet, 
&c. 
The  author  suggests  to  those  having  authentic  samples  of  oil  of 
peppermint,  to  endeavor  to  ascertain  the  cause  of  this  different  beha- 
vior. 
Ampelopsis  hederacea.  The  juice  of  the  berries  was  examined  by 
Von  Gorup-JBesanez,  who  found  the  same  constituents  previously 
obtained  from  the  leaves,*  except  glycolic  acid. — Buchner's  N.  Repert* 
1874,  p.  181. 
The  Flotvers  of  Tilia  argentea,  Desf.,  have  been  met  with  in  Europe 
as  a  substitute  for  the  flowers  of  T,  parvifolia  and  grandifolia,  Ehrh. 
The  former  species  is  cultivated  in  Europe  as  an  ornamental  tree ;  its 
flowers  have  larger  bracts,  which  are  of  a  greener  color  than  the  offi- 
cinal, finely  reticulate  above,  and  underneath  densely  covered  with 
*See  American  Journal  of  Pharmacy,  1871,  p.  164. 
f  Ibid.,  1873,  p.  447. 
*  See  American  Journal  of  Pharmacy,  1872,  p.  165. 
