Newsgroup: it.hobby.pescare
Titolo: star light

Salve,
una curiosita':
qualcuno sa dirmi il principio chimico che fa diventare luminosi gli
starlight?
grazie

Pasquale wrote:

Ti spedisco una risposta in inglese dove c'è anche la reazione che
avviene dentro al tubetto delle nostre cosidette Star Light.
 The following produce rather spectacular results.  Chemicals are
 available through Fluka and Aldrich.  The dyes are expensive.
  Dyes:-
  9,10-bis(phenylethynyl)anthracene (BPEA) (yellow) [10075-85-1] Fluka
15146
  9,10-diphenylanthracene (DPA)             (blue)  [1499-10-1]  Fluka
42785
  5,6,11,12-tetraphenylnaphthacene (rubrene) (red)  [517-51-1]   Fluka
84027
  Other reagents required:-
  bis(2-carbopentyloxy-3,5,6-trichlorophenyl)oxalate (CPPO)
                                              [75203-51-9]  Aldrich
39,325-8
  bis(2-ethylhexyl)phthalate (DOP) (solvent)        [117-81-7]   Fluka
80032
  sodium salicylate (catalyst)                      [54-21-7]    Fluka
71945
  35% hydrogen peroxide                             [7722-84-1]  Fluka
95299
  Saturate solvent with dye and CPPO. Sonicate to help solvation. Start
with
  about 50 mg dye (BPEA, DPA or rubrene) in 10 g solvent with 50 mg CPPO
and
  5 mg sodium salicylate.  CPPO is limiting reagent.
  Put small quantity (20 drops) in a small vial and add equal volume of
  hydrogen peroxide.  Mix vigorously. There will be two phases. Avoid
skin
  contact! Don't cap tightly!
  The oxidant is hydrogen peroxide contained in a phthalate ester
solvent.
  The concentration is very low, less than 0.5%.  The fluorescing
solution
  consists of a phenyl oxalate ester and a fluorescent dye.  The dye
used is
  9,10-bis-(phenylethynyl)anthracene (for green) or
9,10-diphenylanthracene
  (for blue).
  Here is the reaction sequence:
  1)  (Ph)-O-CO-CO-O-(Ph) + H2O2 --> (Ph)-O-CO-CO-O-OH + (Ph)-OH
  2)          (Ph)-O-CO-CO-O-OH  -->  O-O
                                      | |    +  (Ph)-OH
                                     OC-CO
  3)                 C2O4 + Dye  --> Dye* + 2CO2
  4)                        Dye* --> Dye + hv
  In 1) The hydrogen peroxide oxidizes the phenyl oxalate ester to a
  peroxyacid ester and phenol. The unstable peroxyacid ester decomposes
to
  the cyclic peroxy compound and more phenol in step 2). The cyclic
peroxy
  compound is again unstable and gives off energy to the dye as it
decomposes
  to the very stable carbon dioxide. The dye then radiates this energy
as
  light.
An alternative chemiluminescence demonstration involves the H2O2
oxidation
of lucigenin ( bis-N-methylacridinium nitrate [2315-97-1] Aldrich
B4,920-3 ),
[ [1] v.1 p.180-185 ] which has recently been modified to provide a slow
colour change across the visible spectrum [2]. One of the reagents in
that
lucigenin oxidation ( Rhodamine B ) is a mutagen and suspected
carcinogen.
18.2  How do hand warmers work?, and how can I make one?
They consist of an aqueous solution of sodium acetate with a small
"clicker"
disk to impart a physical shock. The solute is dissolved into solution
by
prior warming. when the heat is required, the disk is "clicked" to shock
the
solution, and this causes the sodium acetate to crystallise from the now
supersaturated solution. The heat of crystallisation is slowly released.