Royal Institute of France. 391 
M. Dulong of Alfort has detailed some experiments on the 
oxalic acid, which, although they do not form a complete series, 
nevertheless hold out some interesting prospects in science. On 
saturating this acid with barytes, strontian, or lime, salts are ob- 
tained which always represent the acid employed, even after they 
have been exposed to a heat superior to that of boiling water ; but 
with oxide of lead or zine we always lose twenty per cent. of the 
acid by desiccation. On burning these dried metallic oxalates' af- 
terwards, no water is obtained ; but we obtain carbonie acid, gase- 
ous oxide of carbon, and there remain the oxides of the metals 
employed, among which that of lead presents peculiar properties. 
The oxalates of copper, silver, and mercury, always give, on 
the contrary, water on decomposition, however much dned, at 
the same time with carbonic acid, and the residue is in the metal- 
lic state. A detonation is produced by the oxalate of silver, 
and we know besides that it detonates on being compressed, as 
well as the oxulates of mercury. 
As to the oxalates of barytes, strontian, and lime, they give 
on being decomposed by heat, empyreumatic oil, water, oxide of 
carbon, carbonated hydrogen, and carbonic acid, and there re- 
mains a mixture of subcarbonate and charcoal. * 
These phenomena may be accounted for in two ways: 
Either the oxalic acid must be composed solely of carbon and _ 
oxygen, in proportions intermediate between those of the carbo- 
nie acid and the oxide of carbon; but it contains water, which 
certain oxalates, like those of lead and zinc, give off when dried, 
while the rest retain it; or rather it must be composed of car- 
bonie acid and hydrogen. This last with the oxygen of the 
oxide will form water, which the first oxalates allow to escape, and 
there will only remain the carbonic acid and the metal, a new com- 
bination in chemistry; for it has been generally understood that 
the metals cannot be united with the acids until they are oxi- 
dated. M. Dulong, who inclines towards this last explanation, 
therefore, thinks that these oxalates of lead and of zine, when 
dried, are not true oxalates; and he proposes to give them, as 
well as to any combinations of the same kind which may he dis- 
covered, the name of carbonides. As to the oxalates which do 
not give off water in drying, they will contain the oxalic acid 
entire; and as after its composition it will in future be called 
hydrocarbonic, the salts themselves will be called hydrocar- 
Lonates, 
M. Dulong has been led by analogy to very general conclu- 
sions, by which he brings under the same laws not only the com- 
mon acids, but also the hydracids; but we shall give a more 
detailed report when he has sent us the full accounts which he 
has promised, 
Bb4 The 
