100 



CHEMISTRY. (CHEMICAL PHYSICS.) 



Simultaneously with the observation of the latent 

 emanating power of thorium nitrate, it was no- 

 ticed that preparations of thorium carbonate 

 varied enormously in radiating power according 

 to the method in which they were prepared. In 

 the course of the experiments to which these 

 observations led, it was found that active fil- 

 trates produced under Various conditions de- 

 scribed by the authors contained no thorium, or 

 at most only a minute trace, but another sub- 

 stance in very appreciable quantities which when 

 precipitated with sodium phosphate appeared as 

 a white substance possessing both emanating 

 power and radio-activity many hundredfold 

 greater than those of thorium. This substance 

 lias not yet been obtained in sufficiently large 

 quantities for an exhaustive chemical investiga- 

 tion, and it is impossible at present to say what 

 it may prove to be. The authors do not believe, 

 however, that it is the radio-active or the emana- 

 ting constituent of thorium. The evidence of a 

 series of observations leads to the conclusion that 

 the major part of the radio-activity of thorium 

 ordinarily about 54 per cent. is due to a non- 

 thorium type of matter (Thx) possessing dis- 

 tinct chemical properties, which is temporarily 

 radio-active, its activity falling to one-half its 

 volume in about four days. The constant radio- 

 activity of thorium is maintained by the produc- 

 tion of this material at a constant rate. Both 

 the rate of production of the new material and 

 the rate of decay of its activity appear to be in- 

 dependent of the physical and chemical condition 

 of the system. The Thx further possesses the 

 property of exciting radio-activity in surround- 

 ing inactive matter, and about 21 per cent, of the 

 total activity under ordinary circumstances is 

 derived from this source. Its rate of decay and 

 other considerations make it probable that it is 

 the same as the excited radio-activity caused by 

 the thorium emanation, which has been shown 

 to be produced by Thx. There is evidence that 

 if by any means the emanation is prevented from 

 escaping in the radio-active state, the energy of 

 the radiation goes to augment the excited radio- 

 activity in the compound. Thorium can be freed 

 by suitable means from both Thx and the ex- 

 cited radio-activity which the latter produces, 

 and then possesses an activity about 25 per cent, 

 of its original value, below which it has not been 

 reduced. The residual radiation consists entirely 

 of rays non-deviable by the magnetic field, where- 

 as the other components comprise both (leviable 

 and undeviable radiations. Most probably, the 

 authors suggest, this residual activity is caused 

 by a second non-thorium type of matter, pro- 

 duced in the same changes as Thx, and it should 

 therefore prove possible to separate it by chem- 

 ical methods. 



T. W. Richards predicates two conceivable 

 causes of compression in a substance. The pres- 

 sure may be applied from the outside or it may 

 be due to the internal attraction or affinity of 

 the smallest particles of the substance for one 

 another. That is, the substance may be com- 

 pressed either by an outside pressure or by the 

 intensity of its own cohesion. The former* cause 

 may be typified by highly compressed gases, the 

 second by liquids. In solids we must consider 

 also the directive agency which manifests itself 

 in crystalline form and optical structure. The 

 presence of tfte crystal-making force complicates 

 -the phenomenon, and is a considerable stumbling- 

 block to the study of the theoretical tension of 

 solids. In view of these facts, it seemed to the au- 

 thor possible that the study of compression as 

 manifested by atomic volume under different cir- 



cumstances, as well as of atomic compressibility, 

 might afford some light as to the affinities at 

 work. The outcome of the author's first studies, 

 of which an account was communicated to the 

 American Academy of Arts and Sciences, is that 

 atomic volume is not constant, but is a function 

 of pressure and temperature, and, probably, of 

 electric stress. 



Enumerating some of the results that had been 

 attained in low-temperature studies (with liquid 

 air and liquid hydrogen), Prof. James Dewar said 

 at the British Association meeting that the great 

 majority of chemical actions are entirely sus- 

 pended; but fluorin is still active at the tem- 

 perature of liquid air. Whether solid fluorin 

 and liquid hydrogen would interact, no one can 

 at present say. Bodies naturally become denser, 

 but even a highly expansive substance like ice 

 does not appear to reach the density of water 

 at the lowest temperature, a fact confirmatory 

 of the view that the particles of matter under 

 such conditions are not packed in the closest 

 possible way. The force of cohesion is greatly 

 increased at the extremely low temperature, as 

 is shown by the additional stress required to 

 rupture metallic wire. This fact is mentioned 

 as being of much interest in connection with 

 two conflicting theories of matter: that of Lord 

 Kelvin, that the forces which hold together the 

 particles of bodies may be accounted for without 

 assuming any other agency than gravitation, or 

 any other law than the Newtonian; and the 

 opposite view, that the phenomena of the aggre- 

 gation of molecules depend upon the molecular 

 vibration as a physical cause. Hence, accord- 

 ing to this theory, at the zero of absolute temper- 

 ature, the vibratory energy being in complete 

 abeyance, the phenomena of cohesion should 

 cease to exist, and matter generally be reduced 

 to a heap of cosmic dust. The second view re- 

 ceives no support from experiment. 



The photographic action of light is diminished 

 at the temperature of liquid air to about 20 per 

 cent, of its ordinary efficiency, and at the still 

 lower temperature of liquid hydrogen only about 

 10 per cent, of the ordinary sensitivity remains. 

 At the temperature of liquid air and liquid 

 hydrogen a large range of organic bodies, and 

 many inorganic ones, acquire under exposure to 

 violet light the power of phosphorescence. Such 

 bodies glow faintly so long as they are kept cold, 

 but become exceedingly brilliant during the 

 period when the temperature is rising. Even 

 solid air is a phosphorescent body. All the alka- 

 line earth sulfides which phosphoresce brilliant- 

 ly at the ordinaiy temperatures lose this prop- 

 erty when cooled, and have it renewed on heat- 

 ing; but such bodies may be stimulated through 

 the absorption of light at the lowest tempera- 

 tures. Radio-active bodies, on the other hand, 

 like radium, which are naturally self-luminous, 

 maintain their luminosity unimpaired at the 

 very lowest temperatures, and are still capable 

 of inducing phosphorescence in bodies like the 

 platino-cyanids. Some crystals become for a 

 time self-luminous when cooled in liquid air or 

 hydrogen, owing to induced electric stimulation 

 causing discharges between the crystal molecules. 

 This phenomenon is very pronounced with ni- 

 trate of uranium and some platino-cyanids. 



A long scries of experiments were made by 

 Prof. Dewar and Prof. Fleming on the electric 

 and magnetic properties of bodies at low tem- 

 peratures such as the thermoelectric powers of 

 pure metals, the magnetic properties of iron and 

 steel, dielectric constants, the magnetic and elec- 

 tric constants of liquid oxygen, and magnetic 



