198 
DR. GLADSTONE ON CIRCUMSTANCES MODIFYING 
„ , , , - Water added to 
Sulphateof comparative 
potash added. 
Sulphateof Water added to 
potash added. comparative 
^ solution. 
3*7 measures = 12*5 measures. 
11 '2 measures = 27'5 measures. 
20 measures = 37*3 measures. 
30 measures = 47*5 measures. 
This is exhibited in Plate IX. fig. 3. 
The monobasic pyrorneconate appears therefore to be similar in its testimony to 
the tribasic meconate. 
Ferric Acetate. 
Similar experiments to those already described were made with the acetate of iron. 
As the red colour of this salt is very slight, as compared with that of the preceding 
compounds, it necessitated the employment of tolerably strong solutions. 
Twelve equivalents of acetate of potash were added to one equivalent of each of 
the ferric salts, and gave the following proportions: — 
1 eq. ferric nitrate + 12 eq. acetate of potash gave 100 parts of red salt. 
1 eq. ferric chloride + 12 eq. acetate of potash gave 139 parts of red salt. 
1 eq. ferric sulphate + 12 eq. acetate of potash gave 112 parts of red salt. 
1 eq. ferric citrate + 12 eq. acetate of potash gave no red salt. 
These proportions differ greatly from those which have been previously observed. 
The effect of successive additions of acetate of potash was tried : — 
Ferric Acetate 
nitrate. of potash. 
Red salt 
produced. 
Ferric Acetate 
nitrate. of potash. 
Red salt 
produced. 
1 equiv. + 3 equivs. 
88 
1 equiv. + 21 equivs. 
87 
1 equiv. -f 6 equivs. 
109 
1 equiv. + 30 equivs. 
64 
1 equiv. + 9 equivs. 
109 
1 equiv. f 39 equivs. 
6l 
1 equiv. + 12 equivs. 
102 
1 equiv. + 48 equivs. 
52 
1 equiv. + 15 equivs. 
96 
1 equiv. + 63 equivs. 
46 
Plate IX. fig. 4 exhibits these numbers : and here again, as in the case of the meco- 
nate, there is something producing a great irregularity of action. 
To a mixture of one equivalent of ferric nitrate and three of acetate of potash, suc- 
cessive portions of the iron salt were added. They rendered the mixture much paler, 
reducing it at last almost to the colour of the nitrate itself. 
In order to ascertain whether these changes of colour were due to the formation of 
double salts containing both iron and potash, three equal portions of the ferric acetate 
employed in the previous experiments were treated respectively with solutions of 
acetate of potash, acetic acid, and water. The potash salt caused a slight increase of 
colour, and the pure acid a great decrease, as compared with the effect of mere dilu- 
tion. It is clear that there exist different combinations of acetic acid and sesqui- 
oxide of iron ; indeed, it has been observed before by others, that a highly coloured 
solution of ferric acetate will spontaneously deposit red oxide and become almost 
colourless. 
