THE ARGUMENT 265 



demonstrated that very few elements, prob- 

 ably only silicon, and perhaps boron, can 

 even be imagined in such a role. It h;i>. 

 moreover, just been shown that there are 

 many facts leading to the conclusion that 

 only carbon among elements, and carbon itself 

 only in conjunction with hydrogen, has the 

 power to form the skeletons of compounds 

 numerous, complex, and varied like those of 

 organic chemistry. But, apart from this 

 conclusion, it is certain that silicon and boron 

 could not be mobilized like carbon. Quartz, 



of any known liquid. The critical temperature of ammonia 

 is abnormally high, and its critical pressure — the more char- 

 acteristic constant — is higher than that of any other liquid 

 excepting water. Ammonia is an associated liquid, and its 

 dielectric constant, though much below that of water, is still 

 high when compared with that of non-electrolytic solvents. 

 Its boiling-point elevation constant is the lowest of any 

 known liquid, namely 3.4, as compared with .V2 for water. 

 In its tendency to unite with salts and other compounds, it 

 probably exceeds water, since salts with ammonia of crystal- 

 lization are perhaps even more numerously recorded in the 

 literature than are salts with water of crystallization. As a 

 solvent for salts it is generally much inferior to water, though 

 some salts, for example the iodides and bromides of mercury, 

 lead, and silver, dissolve very much more abundantly in 

 ammonia than they do in water, and it far surpasses the latter 

 solvent in its ability to dissolve the compounds of carbon. 

 Finally it exhibits conspicuous power as an ionizing solvent, 

 the more dilute ammonia solutions at .'>:>. 5° being very much 

 better conductors of electricity than aqueous solutions of the 

 same concentration at 18°." 



