1819.) History of Anthrazothionic Acid. 49 
in a glass tube, large drops of water are deposited in the cool 
part of the tube. We must, therefore, consider it as a hydrate ; 
and the proportions of the constituents as given by Porrett 
require to be altered. _ 
Three grains of the hydrate being exposed to heat till they 
became dark coloured gave out $ er. of water. Hence it follows 
that + of the weight of this hydrate is water. 
It is obvious likewise that the metal must exist in the hydrate 
in the metallic state, since the hydrogen of the acid reduces the 
oxide, a fact which can be evidently observed even during the 
formation of this hydrate; for when the alcoholic solution of 
anthrazothionate of potash is mixed with liquid acetate of 
copper, we can perceive at the instant of the mixture a brown 
copper colour upon the surface of the liquid, which disappears 
after the hydrate is completely formed. In this case either the 
alcohol or the acetic acid must act the part of a disoxidizing 
body. The necessity of the presence of this intermediate sub- 
stance shows that the hydrate can be formed only by means of 
the sum of the affinities of the oxygen for the hydrogen, and of 
the anthrazothion for the metal. 
Sect. 15.—As we can employ as disoxygenizing substances 
bodies which possess that property in a far smaller degree than is 
necessary to change the peroxide of copper into protoxide, it 
follows as a consequence that these disoxygenizing substances 
‘actually separate from the oxide much less oxygen than would 
be requisite in order to convert it into protoxide. The remaining 
part of the task is performed by the hydrogen of the anthrazo- 
thionic acid. We will assume, therefore, that the disoxygenizing 
medium deprives the oxide of 1th of its oxygen, while the 
remaining #ths unite themselves to the hydrogen of the acid at 
the same instant that the metal combines with the anthrazothion, 
and with the water produced forming an anthrazothionhydrate 
of copper. The accuracy of this assumption will still further 
appear from this, that we shall find in quite another way exactly 
as much hydrogen in the acid of the hydrate as is sufficient for 
saturating +ths of the oxygen, which the oxide contains. I may 
mention as a second corroboration of the truth of this assump- 
tion, that the hydrate contains exactly as much water as is 
capable of being formed by the union of 4ths of the oxygen of 
the oxide with the hydrogen of the acid; namely, ith of the 
weight of the whole compound as was shown in the last para- 
graph. 
sect. 16.—Porrett found that 4-58 gr. of anthrazothionhydrate 
of copper contain 2°56 gr. of metal, which require 0°64 gr. 
oxygen to be converted into oxide. According to our view of 
the subject, 1th of this oxygen = 0:128 gr. unites with the 
disoxygenizing medium. There remain, therefore, +ths of 0-64 
= 0°512 gr. of the oxygen, which unite with the hydrogen of 
the anthrazothionic acid to form water. When, therefore, 2°56 
Vou. XIII. N°T. Dd 
