1532 
The very slight difference between the constants of the two @- 
methylglutaconie acids makes us already suspect that we are not 
dealing here with an ordinary pair of cés-trans-isomerides. 
Compared with the unsaturated acids belonging to the suecinie 
series the influence of the double bond is but very slight; for in- 
stance, the ratio between mono-alkylfumaric acids and their cor- 
responding alkylsuceinie acids is + 10:1 and so far as has been 
ascertained still considerably higher with the maleic acids. In these 
acids, however, both carboxyl groups are attached to the doubly- 
linked carbon atoms, whereas in the glutaconic acids this is only 
the case with one. This influences no doubt in a considerable degree 
the dissociation constant. 
I deemed it of importance to determine the dissociation constant 
of this acid also at a still higher temperature; for, a priori, the 
possibility was not exeluded that at a higher temperature isomeri- 
sation would set in, which would then be recognisable by an abnor- 
mal and falling dissociation constant. 
The measurements, however, showed that there was no question 
of isomerisation; the constant was perfectly normal. They were 
executed at 45°.0 in a conductivity-vessel furnished with a ground 
glass stopper, so as to prevent the evaporation of the solution. Still 
the bridge-reading was not yet quite constant. uy, was determined 
\ 
by interpolation from the values deduced by Lurpér ') for other 
temperatures. 
The results were as follows: 
=> 486. 
Vv ap 2 Kk 
31.319 | 33.44 0.0685 1.61>< 10-4 
34.601 | 34.97 720 1.61 
62.758 | 46.40 951 1.59 
69.381 48.97 0.101 1.63 
125.52 65.00 | 133 | 1.63 
138.76 | 67.92 | 140 | 1.64 
| 
251.03 | 90.73 | 186 | 1.69 
| 
| | 
277.53 Hye OFAN chose u Maele 
| 
Mean: Ket — AGA O en 
1) Samm. chem. und chem.-techn. Vortr. XIV 1/3 pg. 11. The relation between 
ko and the temperature is fairly well a linear one. 
