1909] on Advances in Knowledge of Silicon. 647 



represented in the following manner — A, B and C, being" used to 

 indicate the different complex replacing radicles : — 



^H 



SilH 



\H 



In this way silicon alcohols were built up which proved to be 

 analogous to well-known carbon alcohols, and which afforded 

 analogous acids, etc., on oxidation. These discoveries laid the 

 foundations of a silico-organic chemistry and have been further 

 extended in later years. For example, it has been found possible to 

 pursue the analogy with known carbon compounds in the direction 

 of replacing all the hydrogen in silicon hydride by different radicles, 

 and these changes, which can be effected in successive stages, may be 

 represented in harmony with those just given : — 



The two last of these are asymmetric, since all four radicles are differ- 

 ent. Consequently they should exist in two isomeric modifications, if 

 really analogous to known carbon compounds of the same order, and each 

 form should be capable of acting differently on polarised light.* Dr. 

 F. Stanley Kipping, who has specially investigated this kind of sub- 

 stitution with much success, finds that the analogy between these 

 asymmetric silicon and carbon compounds is complete in regard to 

 optical activity as to other general characters. 



Silicon Compounds including Nitrogen. 



This was all good so far as it went, but some highly important 

 information was still wanting. As you know well the various com- 

 pounds ir eluding carbon and nitrogen play by far the most important 

 parts in building up organised structures under the influence of vital 

 energy, bat in the silicon series we were almost wholly ignorant of the 

 existence of such compounds until within recent years when 1 under- 

 took to definitely investigate this branch of the subject. 



All thai", was known at the period of which I speak was that silicon 

 forms a white nitride of uncertain composition when strongly heated 

 in an atmosphere of nitrogen gas ; and that when silicon chloride is 

 brought in contact with ammonia and similar substances violent action 

 occurs, but the nature of the products formed was not known owing 

 to special practical difficulties in separating them. 



The first step taken was to examine the action of silicon halides 



* These changes are represented a^ove as having been effected through the 

 silicon alcohols in order to avoid coinplicating the general statement, other 

 compounds have in fact been found more convenient for the purpose. 



Vol. XIX. (No. lOii) 2 u 



