( i^^)0 ) 



passes into Na.^ Si Fl„. VW allowing llicir apparatns to cool for 2 

 to 3 hours whilst transmitting this gas Hempkl and von Haasy 

 practically converted the sodium iluoride, which had been formed 

 according to the ecpiation: 4 Na + Si FI4 — 4NaFl -)-Si, into sodium 

 fluosilicate, which is soluble in water with great difficulty. Tf, how^ever 

 tlie action of Si Fl^ is stopped as soon as all the sodium has been 

 introduced into the apparatus, it is easy to almost completely avoid 

 the formation of Na.^ Si Fl„. 100 grams of sodium yielded to Mr. 

 Slijper 219 grams of crude material (4 Na FJ -}- Si) instead of 21 3.6 

 the quantity calculated ; 55 grams of the Na gave 119 grams, 

 theory 117.2, and in some further experiments the theoretical 

 cpiantity was but little exceeded. Hy washing and boiling with water 

 and Avith dilute hydrochloric acid the 119 grams were reduced to 

 20 grams whilst the piodiict may contain 16.7 grams of silicon. 

 The product so oblaijied is not, however, pure amorphous silicon, 

 only about 40 i)er cent is volatiliseil in a current of chlorine and 

 may be condensed as silicon chloride, and a residue is obtained, 

 which is oidy to a slight extent soluble in water and principally 

 consists of silicon dioxide. 



This must have been formed during the washijig; fur if the crude 

 product is heated in a current of chlorine there remains besides 

 sodium chloride only a very small (|iiantity of insoluble residue. As 

 the crude product when immersed in water causes a visible evolution 

 of gas with the odour of Si H, it is probable that the Si O^ has 

 been formed by decomposition of Si H^ which may have been pro- 

 duced by the action of ANater on some sodium silicide. Moissan has 

 recently shown that on treating silicoii with boiling water the dioxide 

 of that element is formed. 



2. In accordance with He.mpel and von Haasy, Mr. Seuper found 

 that on heating the crude product in a current of chlorine not a 

 trace of silicon chloride is obtained. As the said product consists 

 mainly of 4 Na Fl -|- Si, it was surmised that this must be attributed 

 to the fact that the primary formed silicon chloride reacts with 

 sodium fluoride according to the eciuation 



Si CI, + 4 Na Fl = Si Fl, + 4 Na CI 



It appeared indeed that on heating sodium fluoride or sodium 

 fluosilicate in the vapour of silicon chloride the said decomposition 

 takes place. If, therefore, chlorine is passed over a mixture of Si 

 and Na Fl as is present in the crude product the reaction nuist 

 proceed in this mamier : 



Si -1- 4 CI + 4 Na Fl = Si Fl, + 4 Na CI. 



