1816.) Royal Institute.of France. 23, 
memoir on hygrometry, containing the immediate consequences of 
these experiments; but these works not having, in his opinion, 
acquired that precision and order which he is accustomed to give to 
all that he publishes, the author has thought proper to defer the 
printing of them. 
M. Dulong, Professor at Alfort, has presented some experiments 
on oxalic acid, which, though not constituting a complete work, 
open interesting views for the science. When this acid is saturated 
with barytes, strontian, or lime, we obtain always salts, which 
represent the acid employed even when they have been exposed to 
a heat higher than that of boiling water. But with oxide of lead, 
or of zinc, we always lose 20 per cent. of the acid by drying. 
When these metallic salts are afterwards strongly heated, no water 
makes its appearance ; but we obtain carbonic acid and carbonic 
oxide, and there remains behind the oxides of the metals employed, 
of which that of lead possesses particular properties. ‘The oxalates 
of copper, silver, and mercury, on the contrary, always give out 
water when decomposed, how dry soever they are previously made. 
Carbonic acid is likewise given out, and the base remains in the 
metallic state. The oxalate of silver detonates, and we know 
already that it detonates when struck, as well as the oxalates of 
mercury. 
As to the oxalates of barytes, strontian, and lime, they give, 
when decomposed by heat, empyreumatic oil, water, carbonic 
oxide, carbureted hydrogen, carbonic acid, and there remains a 
mixture of subcarbonate and charcoal. 
These phenomena may be explained two ways. Oxalic acid is 
either composed entirely of carbon and oxygen, in proportions 
intermediate between those of carbonic acid and carbonic oxide; 
but it contains water, which certain oxalates, as those of lead and 
zine, lose when dried; while others retain it. Or it is a compound 
of carbonic acid and hydrogen. This last constituent, with the 
oxygen of the oxide, will form water, which these first oxalates 
likewise allow to escape, and nothing remains but carbonic acid and 
the metal, a combination quite new in chemistry: for it is re- 
garded asa general principle, that metals are capable of uniting 
with acids only after being oxydised. M. Dulong, who is inclined 
to this last explanation, conceives of course, that the dried oxalates 
of lead and zinc are uot reul oxalates, and he proposes to give to 
them, as well as to similar compounds that may be discovered, the 
name of carlonides. The oxalates which do not give water by 
drying, contain the oxalic acid entire; and as from its composition 
it will be named hereafter hydro-carbonic, the salts will take the 
the name of hydro-carbonates. 
M. Dulong is led by analogy to very general conclusions, by 
which he reduces under tlie same laws, not only the ordinary acids, 
‘but likewise the hydracids. But we shall give a more detailed 
account of his opinions, when he sends up the memoir in which he 
intends to consign them. : . 
The chemical action of solar light on bodies is worthy of all the 
