NOTE ON THE OXALATE OF IRON. 19 
more than the ordinary oxalate of iron containing two equivalents of 
water, Fe O, C?0°+2 aq. This compound has been described by 
Vogel and Berzelius, its composition shown by Débereiner and Kam- 
melsberg, who appear to have proved that it differs from the rare 
mineral Humboldtite in containing half an equivalent more water, 
Fe O, C?0° +1} aq and Fe O, C203 +2 aq, or ane 0* + 3 aq and 
“ae hot+4 aq, corresponding to the manganous oxalate. More 
recently it has been examined by Souchay and Lenssen, in their 
extended investigation of the oxalates. 
In order to test the matter still further, the Att was prepared by 
my pupils, Mr. Ramsay and Mr. Thomson, in both ways indicated by 
Dr. Phipson, using a large excess of oxalic acid in the one case, and 
precipitating both from concentrated and from very dilute solutions, 
in both cases the precipitation takes place almost immediately. 
The subjoined quantities of FeO were obtained. It will be ob- 
served that the amount of Fe O is a little below the requisite quan- 
tity, both in these analyses and in those of Rammelsberg which are 
appended, owing to the salt retaining a certain amount of hygroscopic 
water, unless dried for a long time at 100°, and also to the fact that 
when heated it is not perfectly oxidized unless the heat be continued 
for a long time or the residue be moistened with nitric acid and again 
heated, as was done in No. 1; No. IV was only air dried. 
Cal’d. I II II IV 
Fe O—1-36-40 — 39°70 — 38:91 — 38:68 — 38:08 
C?03— 1-36-40 — 
H O— 2-18-20 — 
90 100 
Fe O — Rammelsberg — 38°78 — 39°10 — 38:92 — 38°84 — 39°48 
University College Laboratory, Dec., 1860. 
The 17th number of the Comptes Rendus having come to hand, the 
writer is enabled to give the analyses on which the above formula is 
founded, viz: Fe O—19°35—19°44 
C?03—80-65—80°56 
100:00 100:00 
From the exact accordance of the analyses it is evident that the oxalic 
acid was not determined, but only calculated from the loss, and as the 
