PROBLEMS OF INORGANIC CHEMISTRY. 37 



with phosphoretted and arsenicoretted hydrogen, especially at low 

 temperatures. 



The progress of chemical discovery, indeed, is closely connected 

 with the invention of new methods of research, or the submitting of 

 matter to new conditions. While Moissan led the way by elaborating 

 the electric furnace, and thus obtained a potent agent in temperatures 

 formerly unattainable, Spring has tried the effect of enormous pres- 

 sure, and has recently found chemical action between cuprous oxide 

 and sulphur at ordinary temperature, provided the pressure be raised 

 to 8,000 atmospheres. Increase of pressure appears to lower the tem- 

 perature of reaction. It has been known for long that explosions will 

 not propagate in rarefied gases, and that they become more violent 

 when the reacting gases are compressed: but we are met with difficul- 

 ties, such as the non-combination of hydrogen and nitrogen, even at 

 high temperature and great pressure; yet it is possible to measure the 

 electromotive force (0.59 volt) in a couple consisting of gaseous nitro- 

 gen and gaseous hydrogen, the electrolyte being a solution of ammo- 

 nium nitrate saturated with ammonia. Chemical action between dis- 

 solved hydrogen and nitrogen undoubtedly occurs; but it is not con- 

 tinuous. Again we may ask, Why? The heat evolution should be 

 great; the gain of entropy should also be high were direct combina- 

 tion to occur. Why does it not occur to any measurable extent? Is 

 it because for the initial stages of any chemical reaction, the reacting 

 molecules must be already dissociated, and those of nitrogen are not? 

 Is that in any way connected with the abnormally low density of gas- 

 eous nitrogen? Or is it that, in order that combination shall occur, 

 the atoms must fit each other; and that in order that nitrogen and 

 hydrogen atoms may fit, they must be greatly distorted ? But these are 

 speculative questions, and it is not obvious how experiments can be 

 devised to answer them. 



Many compounds are stable at low temperatures which dissociate 

 when temperature is raised. Experiments are being made, now that 

 liquid air is to be purchased or cheaply 'made, on the combinations of 

 substances which are indifferent to each other at ordinary temperatures. 

 Yet the research must be a restricted one, for most substances are solid 

 at — 185°, and refuse to act on each other. It is probable, however, 

 that at low temperatures compounds could be formed in which one of 

 the elements would possess a greater valency than that usually ascribed 

 to it; and also that double compounds of greater complexity would 

 prove stable. Valency, indeed, appears to be in many cases a function 

 of temperature ; exothermic compounds, as is well known, are less stable, 

 the higher the temperature. The sudden cooling of compounds pro- 

 duced at a high temperature may possibly result in forms being pre- 

 served which are unstable at ordinary temperatures. Experiments 

 have been made in the hope of obtaining compounds of argon and 

 helium by exposing various elements to the influence of sparks from 



