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VI. Inquiries respecting the Constitution of Salts. Of Oxalates , Nitrates , Phosphates , 
Sulphates, and Chlorides. By Thomas Graham, Esq. F.R.S. Edin., Professor of 
Chemistry in the Andersonian University of Glasgow, Corr. Member of the Royal 
Academy of Sciences of Berlin, 8$c. Communicated by Richard Phillips, Esq. 
F.R.S. 
Received June 23, — Read November 24, 1836. 
From the results obtained in a former paper upon water as a constituent of sul- 
phates, it seemed likely that a close analogy would generally be found to exist between 
any hydrated acid and the magnesian salt of that acid. The sulphate of water is 
constituted like the sulphate of magnesia ; and so do I now find the oxalate of water 
to resemble the oxalate of magnesia, and the nitrate of water to resemble the nitrate 
of magnesia. Indeed it appears probable that the correspondence between water 
and the magnesian class of oxides (as we may call the metallic oxides isomorphous 
with magnesia) extends beyond their character as bases, — that in certain subsalts of 
the magnesian class of oxides we have the metallic oxide replacing the water of 
crystallization of the neutral salt, or discharging a function which was thought pe- 
culiar to water. 
In the formation of a double sulphate a certain kind of substitution or displace- 
ment was observed, such as the displacement of an atom of water pertaining to the 
sulphate of magnesia, by an atom of sulphate of potash, to form the double sulphate 
of magnesia and potash. The same kind of displacement appears to occur likewise 
in the construction of double oxalates ; and the tracing of it enables us to form an 
idea of the constitution both of the double and of the superoxalates, and to explain 
their derivation, as in the case of the sulphates. 
I. Of the Oxalates. 
The oxalates promised ample scope for investigation from their number and variety. 
For we have not only neutral oxalates, double oxalates, and binoxalates, but likewise 
an unparalleled combination, the quadroxalate of potash, of which the true constitu- 
tion or proximate composition is a most interesting subject of inquiry. 
1. Oxalate of Water, or Hydrated Oxalic Acid. 
H CC H 2 . 
The recent and accurate experiments of Berzelius, Gay-Lussac, and Turner, 
leave no doubt that the crystals of oxalic acid contain three atoms of water. I find 
