( 191 ) 



Tliat such is praclically the case was sliown by the fact that tlie 

 gas evolved consisted of Si Fl^ and that tlie substance left behind 

 in the boat ^vas found to be almost pure sodium chloride. 



A better method of preparing amorphous silicon seemed to be 

 the decomi)Osition of silicon chloride by sodium. When boiled in 

 benzene-solution with sodium or potassium no action took place. 

 A reaction, however, took place on heating sodium in the vapour 

 of silicon chloride, but it became very violent ; the brown powder 

 obtained could certainly be readily freed from sodium chloride by 

 means of water, but on heating in a current of chlorine a large 

 amount of Si 0.^ (about 30 7o) was left behind showing that even 

 this process does not lead to pure amorphous silicon. 



Much more simple is the preparation of cri/,'<taUised silicon accor- 

 ding to the method recently published by R. A. Kühne (Chem. 

 Centr. 1904, 1. 64) if we introduce a slight modification. A mixture 

 of 200 grams of aluminium shavings or powder, 250 grams of 

 sulphur and 180 grams of fine sand is put into a Hessian crucible 

 placed in a bucket with sand. Upon the mixture is sprinkled a thin 

 layer of magnesium powder and this is ignited by means of a 

 GoLDSCHMiDT Cartridge. The mass burns with a beautiful light and 

 the contents of the crucible become white hot. When cold, the mass 

 is treated wWh dilute hydrochloric acid, which dissolves the aluminium 

 sulphide and leaves the silicon in a beautifully crystallised state. 

 The yield amounts to about 30 grams. On heating in a current of 

 chlorine Si Cl^ is very readily formed, only 37o remaining as non- 

 volatile products. It is a material eminently suited for the prepa- 

 ration of Si CI4, but Mr. Slijper did not succeed in converting it into 

 silicon sulphide by heating with sulphur. 



Groningen, Lab. Univers. March 1904. 



Crystallography. — ''(Jn the preservation of the crystallograyhical 

 symmetry in the substitution of j^osition isomeric derivatives of 

 the benzene series". By Dr. F. M. Jaeger. (Communicated by 

 Prof. A. P. N. Franchimont). 



(Communicated in the meeting of June 24, 1904). 



Some time ago when engaged in a research as to the connection 

 between molecular and crystallographical symmetry of position-isomeric 

 benzene derivatives^), I demonstrated, that of the six possible ^;77>rö7?ïO- 



1) Jaeger, Grystallographic and Molecular Symmetry of position-isomeric Benzene- 

 derivatives. Dissertation, Leiden 1903. (Dutch). 



