507 
The presence of nuclei affords an easy explanation of this. Let 
us suppose, for example, that the dissociation of the 68°-acid is 
allowed to proceed so far that there are now only two nuclei 
remaining in 20 mgr. of the substance. 
Suppose also that the substance may now be divided into four 
equal parts. In two parts there are now at the most one nucleus 
each; in the other two parts there is no nucleus. In this way we 
have, using portions of 5 mgr., 50°/, of the substance transformed 
into 42 -acid under the applied conditions of temperature and heating. 
If the substance had not been subdivided, then the 20 mgr. with 
the two nuclei would have been transformed, either immediately or 
after several hours, into 68°-acid.*) It is now easy to see that, if 
the probability of transformation for 5 mgr. is 50°/, it is 25°/, for 
10 mer., 12.5 °/, for 20 mer, 6.25 °/, for 40 mer., etc, that is, the 
probability of complete (ransformation with a given temperature and 
time of heating becomes smaller and smaller as greater quantities 
of substance are used. 
For each experiment STOBBE and SCHöNBURG heated only ten tubes, 
so that the figures obtained by them are certainly not to be used 
as mean values. They found, for example, on heating 5—7 mgr. of 
68°-acid. for 10 minutes at 70° that four tubes out of the ten were 
transformed. (In the case that one part melted at 42° and another 
at 68°, complete transformation was not obtained). At 100° also only 
four of the ten showed a transformation into the 42°-acid. At 70° 
the mean value was probably somewhat lower. If we assume that 
the mean for ten minutes’ heating at 70° was 40°/,, then the 
probability of the conversion of 0.05 gr, in ten minutes is only 
5°/,, that is, the conversion should take place in one experiment 
out of twenty. 
In order to investigate if perhaps atmospheric nuclei were in part 
responsible for the difficulty of the transformation, quantities of the 
68°-acid were melted in U-tubes. One limb of these U-tubes was 
provided with a plug of cottonwool. Through this limb a rapid 
current of air at 70° was drawn during the time the U-tube was 
being heated in a water-bath at 70°, in order to drive out the air 
nuclei through the other limb. 
After the heating the other limb was closed by means of a cotton 
wool plug. Working in this way | was as unsuccessful as Sroppe 
and Scsonsore in transforming 0.05 gr. of 68°-acid permanently 
into 42°-acid by heating for twenty minutes at 70°. 
') This is the reason for the phenomenon, observed by Stopse and Scuönsura, 
that in the capillary tubes some portions melted at 42° and others at 68° or 580, 
