Atomic Volume and Specific Gravity. 511 



these volumes is due to its combined water, the proper num- 

 ber of volumes in anhydrous oxalate of potash is three, and 

 these it carries into binoxalate of potash, which is therefore a 

 simple combination of oxalate of potash and hydrated oxalic 

 acid, the crystalline water pf the.. latter having assumed the 



volume lloq li,' ; , >xo ? t x 8'0 • 



: r . . -■■-. .A Insolution. As a salt. 



KOjC^Og 18 ... 330 



HO,C2 03 + 2HO ... 36 ... 41-6 

 Binoxalate of potash . . . 54 ... 74*6 

 The only difference between the volumes of this salt and 

 those of its constituents, when uncombined, is that the cry- 

 stalline water of the hydrated oxalic acid has assumed the 

 volume 11. Quadroxalate of potash consists of anhydrous 

 binoxalate of potash united to hydrated oxalic acid, as Gra- 

 ham has already announced in his researches on the oxalates. 

 The three volumes affected by oxalate of potash in its solid 

 state pass into solution with it in quadroxalate of potash, just 

 as we saw in the case of chromate and bichromate of potash ; 

 and the attached oxalic acid affects 11x4 instead of 9*8 x4. 

 ';- ':- - Insolution. As a salt. 



r . I. Anhydrous binoxalate of potash 45 ... 52*6 

 "11. Hydrated oxalic acid .... _72 ... 88-0 

 Quadroxalate of potash . . . 117 ••• 140'6 

 I The assumption of two volumes in solution above those of 

 binoxalate of potash was already characteristic of binoxalate 

 of ammonia, and the same increase is seen in the quadroxalate, 

 showing clearly that that salt must contain its ammonia quasi 

 binoxalate and not as oxalate of ammonia. It is very possible 

 that the volumes in solution of quadroxalate of ammonia should 

 be 14, instead of 15, but the temperature 31°, at which it 

 comes out 14 volumes, is so low, that it is more natural to 

 keep the volumes we have given in the table. 



It is interesting to observe how closely oxalate of copper 

 relates itself to oxalate of water. 



Volumes Volumes 



in solution. as salt. 



Oxalate of copper and potash .6 ... ^ 

 water and potash .6 ... 7 

 copper and ammonia 8 ... 8 

 water and ammonia .8 ... 8 

 Thus, even in the apparently anomalous behaviour of bin- 

 oxalate of ammonia, in assuming two volumes more than the 

 corresponding salt of potash, we find oxalate of copper and 

 ammonia imitating its example. The reason of their increase 

 will be explained in the next section. 



