38 
ozone produced b} 7 the electric discharge in air or oxygen. In 1847 
Schoenbein ( 374 ) seems to have published a resume of his work on the 
bluing of guaiacum up to that time, mentioning the reduction of the 
blue compound by. hydrogen sulfide and other reducing agents, and 
the general similarit} 7 between guaiacum-blue and the blue iodide of 
starch. In other still later communications on guaiacum resin ( 375 - 376 ) ? 
he calls attention to the considerable number of substances which have 
the power to blue guaiacum, among which may be mentioned chlo- 
rine, bromine, iodine, ozone, certain peroxides such as those of man- 
ganese and lead, silver oxide, and acetate, cupric chloride, ferric chloride, 
mercuric chloride, potassium ferricyanide, the bichromates and per- 
manganates, and even finely divided platinum. He also points out 
that guaiacum which had been blued by any one of these substances 
gradually loses its blue color on standing, but that this may be restored 
by adding fresh quantities of the reagent. This may be repeated a 
certain number of times, but finally a colorless or brownish product 
of the resin is obtained which is no longer capable of being blued by 
ozone or similar substances. 
He calls attention to the fact that the blue color of guaiacum is 
destroyed by phosphorus, the metals, hydrogen sulfide and selenide, 
sulfurous acid and hyposulfites, ferrous and stannous salts, and by 
acids and alkalis. He also points out that the majority of those sub- 
stances capable of bluing guaiacum contain their oxygen in the pecu- 
liar^ active condition in which this element is met with in ozone. In 
other words, these substances contain oxylisirten or erregten oxygen, or 
can give rise to the same. He points out a number of analogies between 
guaiacum blue and the iodide of starch, as to color, general methods of 
formation by the action of oxidizing agents, conduct towards reducing 
agents, etc., and he reached the conclusion that the blue material 
resulting from the action of ozone on guaiacum is a compound of ordi- 
nary guaiacum with a hydrogen peroxide (ozone), of much the same 
nature as the loose chemical combination met with in the iodide of 
starch. He goes on to say further that — 
I need scarcely remark that for those who with De la Rive and Berzelius look upon 
ozone as nothing but modified oxygen, it is only necessary to assume that guaiacum 
blue consists of a loose combination of ordinary guaiacum and this uncommon oxygen. 
In other words, that it possesses the nature of an organic peroxide which contains at 
least a part of its oxygen in the chemically excited or active condition in which it is 
met with in hydrogen peroxide, ozone, and manganese dioxide. 
Finally, he explained the spontaneous decolorization of guaiacum 
blue and its ultimate conversion into a substance no longer capable of 
yielding the blue compound by treatment with ozone or other oxidiz- 
ing agents, upon -the supposition that the chemically active oxygen 
in loose combination in the blue resin can exist for only a short time 
as such in this compound and that this form of oxygen at ordinary. 
