648 Dr. J. Emerson Reynolds [May 28, 



(i.e. chloride, bromide, etc.) on substances free from oxygen, but rich 

 in nitrogen. The earhest of these worked with were Thio- 

 carbamides, but in all these cases the sihcon hahde merely united 

 with the nitrogen compound as a whole, in some instances producing 

 very curious substances of which the one with Allyl-thio-carbamide 



(C3H, . H3N2CS)8 SiBr^ 



is a good example. This is a liquid which flows so slowly at ordinary 

 temperature that it requires nearly a month in order to fall from the 

 top of its containing tube and find its level at the bottom. Several 

 similar substances have been obtained and examined and their pro- 

 ducts of decomposition studied, but they do not belong to the class of 

 which I was really in search. 



It would weary you to give tbe details of scientific prospecting 

 which one has to go through in order to attain definite results in a 

 new line of work like this, suffice it to say that success attended the 

 efforts at last, and a finely crystallised and perfectly defined com- 

 pound was obtained in which silicon is wholly in direct chemical 

 combination with nitrogen, and a specimen of that substance I now 

 show you. Its composition is represented by the expression 



Si (NHPh)^ 



where Ph stands for the phenyl group, and its name is Silico- 

 phenylamide. 



This substance when heated undergoes some important changes, 

 which resemble rather closely similar changes that can be effected 

 in analogous compounds of carbon with nitrogen. Thus it first 

 affords a guanidine 



/NHPh 

 Si^NPh 

 \NHPh 



analogous to the well-known carbon guanidine, and further a diimide, 

 Si (N Ph)2, which only needs the addition of a molecule of water to 

 convert it into a silicon urea^ SiO (NH Ph)2. Many other substances 

 have been produced similar to silicophenylamide, and they afford 

 analogous products to these just mentioned ; but these have been 

 fully described elsewhere, and need not be dealt with here. 



Silicon in Relation to Organised Structures. 



The general results of these researches are that we now know a 

 considerable number of silicon compounds including nitrogen, which 

 resemble those of carbon with nitrogen both in composition and in 

 the general nature of the changes in which they can take part. Some 

 of these carbon analogues are closely related to those which are con- 

 cerned in building up organised structures of plants and animals. 



