52 
PROFESSOR GRAHAM ON THE CONSTITUTION OF 
9. Oxalates of Ammonia. 
The oxalate and the binoxalate of ammonia agree exactly in composition with the 
corresponding salts of potash, the hypothetic oxide of ammonium being substituted 
for potash. It has been supposed that no quadroxalate of ammonia exists ; but this 
is a mistake. Such a salt is formed, on dissolving together equal weights of binoxa- 
late of ammonia and hydrated oxalic acid, and is analogous in form and composition 
to the quadroxalate of potash. 
10. Oxalate of Soda. 
Na CC. 
This salt is perhaps the least soluble of the salts of soda, and presents itself as a 
granular precipitate on saturating carbonate of soda with oxalic acid. Of the oxa- 
late of soda dried in air without the application of heat, 23'44 grains left 18’52 car 
bonate of soda when strongly ignited, or 100 oxalate yield 70'01 carbonate of soda. 
Now 100 anhydrous oxalate of soda should yield 79'09 carbonate of soda. Hence 
the oxalate of soda is correctly stated to be anhydrous. It nevertheless combines 
with hydrated oxalic acid, and forms a binoxalate. In this compound we have simply 
the attachment of an atom of the oxalate of water, to the atom of oxalate of soda, 
without the displacement of an atom of water, as in the formation of the binoxalate 
of potash. Probably the absence of the atom of water in the oxalate of soda indi- 
cates an indifference on the part of this salt to enter into further combination. There 
is certainly a binoxalate of soda ; but this binoxalate cannot support the further attach- 
ment to it of two atoms of hydrated oxalic acid, and there is no quadroxalate of soda. 
1 1 . Binoxalate of Soda. 
Na CC + H CC II 2 . 
This salt I find to resemble the binoxalate of potash, in containing three atoms of 
water. 22’ 11 grains, strongly ignited, left 8’05 grains fused carbonate of soda; or 
100 binoxalate leave 40'67 carbonate of soda, equivalent to 23*84 soda; while a bin- 
oxalate with three atoms of water should yield 23*95 per cent, soda, or almost exactly 
the experimental result. The binoxalate of soda lost little more than 1 per cent, of 
its weight when kept at 212° Fahr. over sulphuric acid in vacuo. But by a heat 
approaching 300° Fahr. the salt lost 14*64 per cent, of water, which is a little more 
than two atomic proportions, namely, 13*78 per cent. Hence this salt retains the 
whole of its constitutional water at 212°, but loses two atoms of it at a higher tem- 
perature, retaining strongly the third atom of water, which is basic. 
Double Oxalates. 
The number of double oxalates is not so great as is generally supposed. On mixing 
a solution of binoxalate of potash either with the muriate or the sulphate of magnesia. 
