146 
Laboratory  Notes. 
(  Am.  Jour.  Pharm. 
[Mar.,  1874.  SuppL 
The  alkaline  tincture  of  the  root  of  Gelsemium  sempervirens  ;  solu- 
tions of  chlorophyll,  sulphate  of  quinia,  asphaltum  or  aesculin  ;  oil  of 
peppermint  treated  after  Fluckiger's  method  ;  various  petroleum  prod- 
ucts, or  other  liquids  in  which  fluorescence  is  very  strongly  marked,  do 
not  compare  in  intensity  with  the  ether  residue. 
Viewed  by  reflected  light,  the  liquid  is  of  a  deep  green  color,  and 
appears  to  be  perfectly  opaque  ;  by  transmitted  light  it  is  brownish- 
red.  The  degree  of  fluorescence  is  influenced  by  the  purity  of  the 
alcohol  which  has  been  treated  by  the  acid ;  the  intensity  increasing 
with  the  impurities  present.  Methyl  compounds,  especially,  have  an 
intensifying  effect. 
Cement  for  Affixing  Labels  to  Tin  or  other  Metallic  Substances. — - 
Of  the  various  formulae  which  have  been  published,  none  have  given 
such  satisfactory  results  as  that  in  which  tragacanth  mucilage  is  mixed 
with  honey.  Paste  of  this  kind  has,  however,  two  disadvantages — - 
tardiness  in  drying,  and  susceptibility  to  damp.  I  have  found  that 
by  incorporating  or  triturating  with  the  mixture  a  considerable  pro- 
portion of  dry  wheaten  flour,  these  disadvantages  are  very  much 
reduced,  and  the  adhesiveness  and  permanent  tenacity  of  the  film  are 
perceptibly  improved.  I  think  that  those  who  try  this  plan  will  have 
every  reason  to  be  satisfied  with  it.  The  following  proportions  may 
he  used : 
Tragacanth  Mucilage,    .  .  .  .10  parts, 
Honey,       .....  10  parts, 
Flour,    .  .  .  .  .  .1  part. 
A  cement  possessing  better  damp-resisting  properties,  but  having 
the  disadvantage  of  not  being  permanently  adhesive  where  the  sur- 
face of  the  metal  is  at  all  greasy,  and  also  being  objectionable  on 
account  of  its  dark  color  and  liability  to  disfigure  the  label,  is  formed 
by  boiling  together,  until  solution  is  effected,  two  parts  of  shellac,  one 
of  borax  and  sixteen  of  water.  Shellac  dissolved  in  alcohol  will  pro- 
duce a  cement  having  perfect  damp-resisting  properties,  but  the  film 
is  very  apt  to  separate  from  a  polished  surface.  Flour  paste,  to 
which  a  certain  proportion  of  sulphuric  acid  has  been  added,  makes 
a  lasting  paste,  but  the  acid  often  acts  upon  the  metal — especially  if 
exposed  to  damp — and  unsightly  stains  are  produced,  which  penetrate 
the  label.  This  paste  cannot  be  used  for  ordinary  colored  papers,  or 
with  some  colored  inks.   Mixtures  of  flour  paste  with  molasses,  syrups 
