1883.] On the Theory of Phosphorescence. 707 
2. Such as on the addition of alkalies form adtive oxygen 
and become phosphorescent during their combination 
therewith. 
To the first group belong various hydrocarbons, the ter- 
penes, &c. Some of these bodies at once give off light when 
exadtly neutralised with barium peroxide, magnesia, milk of 
lime, or a strong solution of potassa, soda, or even sodium 
carbonate. They phosphoresce with especial beauty if 
heated with dry caustic potassa or soda, as is shown by the 
author’s experiments with the oils of amber, calamus, 
and dill. 
In the second group we find various aldehyds (chiefly 
polymerised), their ammonium compounds, — further, hydro- 
benzamide, lophine, anisidine, furfurine, and many other 
analogous bodies. In short, there belong here either alde- 
hyds or bodies which reproduce aldehyds on treatment with 
alkalies, as the author has already proved in case of 
lophine. 
These bodies, however, are not luminous in watery solu- 
tions, even if they are readily soluble in water ; they must 
be treated with alcoholic solutions of alkalies only. This 
fa 6t attracted the author’s attention some time back, though 
he did not make it public until his researches on lophine 
had shown that this compound, in presence of water and in 
the absence of air, attracts the elements of water, and is 
converted into benzoic acid and oil of bitter almonds. In 
order to explain this fadf the circumstance must not be 
overlooked that aqueous solutions of potassa form with the 
aldehyds chiefly resinous matters, whilst alcoholic solutions 
yield salts of the corresponding acids and alcohols. 
The action is therefore twofold, and the process resolves 
itself into two stages. When the hydrogen which is at 
first liberated comes in contadf with atmospheric oxygen, 
the latter is at once transformed into the active modifica- 
tion, and then follows the chemical process which gives rise 
to phosphorescence. Whether this adtivation of oxygen 
takes place at once according to Hoppe-Seyler’s formula, or 
if hydrogen peroxide is first formed, is perfectly indifferent 
as regards the chemical adt of phosphorescence, for hydro- 
gen peroxide must first eliminate oxygen if the oxidation of 
the aldehyd is to take place. 
In the author’s memoir on the luminosity of fats, such as 
olive and almond oils, cod-liver oil, &c., he has shown that 
even when these bodies no longer phosphoresce, if briskly 
shaken the addition of a few drops of hydrogen peroxide is 
