(318) 
The above case is one of the most striking of those which have 
as yet, come to my knowledge. 
2. In my previous communications on this subject the purity of 
material used in my investigations was but littie commented on. 
As from various quarters the question was put to me in how far 
any impurities contained in the tin might influence the observed 
phenomena, I will now give, some particulars as to the purity of 
the materials used, laying stress on the fact that I had paid the 
necessary attention to this matter from the beginning. 
My material was derived from a block of Banca tin which had 
been procured some 15 years ago for the collection of the laboratory 
and which at the commencement of my investigations was still quite 
intact in the well-known boat-shape. 
How little the composition of Banca tin changes in the course of 
years is proved by the following figures from G. J. MuLDER’s ') 
analyses from the year 1851, who tested blocks sent by 20 different 
ships, and from those of J. D. VAN DER Praars *) from the year 1885, 
Murper (1851) v. D. Praars (1885) 
Fe 0,019 0,015 
Pb _ 0,014 0,017 
Cu 0,006 0.005 
Si a 0,010 
Sn 99,96 99,95 
The figures represent percentages. 
I have submitted 100 grams of my tin toa microchemical analysis 
in which work I had the valuable assistance of Dr. ScHoorL. The 
result of the investigation was that minute traces of lead could be 
detected. Only doubtful reactions could be obtained for the other 
above mentioned elements so if they were present at all, their amount 
must have been particularly small. 
We may, therefore, safely conclude that phenomena previously 
described relate indeed to pure tin. 
Amsterdam, Chemical Laboratory of the University, Dec. 1901. 
1) Scheikundige Onderzoekingen. 5, 529. 
2) C, R, 100, 44 (1885), 
es nd 
