676 
Physics. “The system tin’. By Prof. A. Smits and Dr. H. L. pr Lerow. 
(Communicated by Prof. A. F. HorLEMAN). 
(Communicated of the meeting of October 26, 1912). 
As is known when molten tin is cooled down, the tetragonal modi- 
fication deposits under ordinary circumstances, which form was first 
described by Mirrer *) in 1848. This form shows a point of transi- 
tion at 187), below which the gray tin is the stable modification. 
In the years 1880 and 1881 TRECHMANN®) and Fourron *) disco- 
vered moreover a third modification, viz. a rhombic one, which can 
be formed when molten tin is exceedingly slowly cooled down, and 
which is brittle. 
It was now natural to assume that this form of tin forms at higher 
temperature from the tetragonal modification, for it had been known 
for a long time that tin heated to about 200° becomes brittle, and 
that in England this circumstance has been profitably used to obtain 
the so-called corn tin or grain tin. In this process tin is heated to 
some degrees under the melting-point, after which it is dropped from _ 
a great height on a stone plate, on which the metal breaks up into 
pieces resembling basalt. The above-mentioned supposition was further 
supported by observations by Katiscuer*), in which it appeared that 
when tin is heated to about 200°, the aspect changes, and the metal 
assumes the appearance of moiré métallique. 
As Scuaum') already observed these experimental data make the 
existence of a point of transition at about 200° very probable, and 
as the spec. gravity of the tetragonal and rhombic modification, 
which amount to 7,25 resp. 6,55 at 15° differ pretty much, it seemed 
the natural course to take to try and find this. point of transition by 
a dilatometrical way. CoHeN and GoLDscHmipT’s’) experiments with an 
oil-dilatometer, however, (in which no difficulty was experienced from 
any generation of gas) did not furnish the least indication for the 
existence of a point of transition, for the expansion, represented as 
function of the temperature, appeared to be a perfectly straight line 
from 175° to 210°. Though these experiments had yielded a negative 
result, already a year before Werigin, LEWKOJEFF and TAMMANN *) had 
1) Phil. Mag. (3) 22, 263 (1834). 
2) CoHEN-vAN Eyk, Z. f. phys. Chem. 
3) The mineralogical magazine and Journal of the Mining Soc. 3, 186 (1880). 
4) Verh. der k. k. geologischen Reichsanstalt 1881, 237. 
Jahrb. der k. k. geologischen Reichsanstalt 1884, 367, 
5) B.B. 15, 722 (1118). 
6) Lieb. Ann. 808, 18 (1899). 
7) Z. f phys. chem. 50, (1904). 
3) Drud. Ann. 10. 647 (1903). 
