( 480 ) 
This does not only apply to nitrations, but also in cases of the intro- 
duction of bromine and chlorine. I have met with many instances in 
which it was possible to predict which of the possible isomers would 
be the chief product. 
The question now arises whether the relative quantities in which 
the isomeric trisubstituted derivatives are generated corresponds to 
the relation shown by the above mentioned products, or in other 
words whether the phenomena observed in the formation of trisub- 
stituted derivatives may be explained quantitatively in this manner. 
Researches in this direction are in progress in my laboratory. 
Chemistry. — Prof. H. W. Bakuuis Roozezoom presents in the name 
of Dr. C. van Eyk, of Breda, the following paper: “Forma- 
tion and transformation of the double salt of Silvernitrate 
and Thalliumnitrate.” 
(Read February 24, 1909.) 
1. Silvernitrate and thalliumnitrate are rhombic at the ordinary 
temperature; at 159° and 142° respectively, they undergo a struc- 
tural change and become rhombohedric. No records exist as to the 
formation of mixed crystals. Rercers (Zeit. phys. Chem. 5, 451) 
mentions the existence of a double salt without mentioning however 
whether he has obtained this from the aqueous solution or from the 
fused mixture. The object of this investigation was to see what 
kind of crystals are deposited from fused mixtures of various con- 
centrations (varying from 100 per cent of silvernitrate to 100 per 
cent of thalliumnitrate) and to study the possible changes which 
these crystals undergo at lower temperatures. 
2. Determination of the meltingpoint line. 
The solidifying points of mixtures of Tl NO; and Ag NOs (varying 
from 0 to 100 percent) were observed and the course of the 
solidification was watched. 
It was found that the meltingpoint line, starting from either 
TINO; or Ag NO, took a descending course with a short double 
salt line situated between the two branches. 
Mol. pCt. Ag NO, Commencement of Solidification. 
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