98 



CHEMISTRY. (CHEMICAL THEORY.) 



hypotheses proved unsatisfactory. It is appar- 

 ent that in radio-activity we are dealing with 

 phenomena outside of the sphere of known 

 atomic forces, for the whole process goes on in- 

 dependently of temperature and chemical affinity. 

 The idea of the chemical atom in certain cases 

 spontaneously breaking up with evolution of 

 energy is not of itself contrary .to anything that 

 is known of the properties of atoms. The 

 changes brought to knowledge by radio-activity, 

 although undeniably material and chemical in 

 nature, are of a different order of magnitude 

 from any that have been before dealt with in 

 chemistry being of an extreme order of minute- 

 ness. It is a significant fact that the radio-ac- 

 tive elements are all at the end of the periodic 

 table. If we suppose that radium is the missing 

 second higher homologue of barium, then the 

 known examples uranium, thorium, radium, 

 polonium (bismuth), and lead are the five ele- 

 ments of heaviest atomic weight. Nothing can 

 yet be said of the mechanism of the changes in- 

 volved ; but whatever view is ultimately adopted, 

 it seems not unreasonable to hope that radio- 

 activity affords the means of obtaining informa- 

 tion of processes going on within the chemical 

 atom. 



The radio-active elements are considered by 

 Mr. Geoffrey Martin, of the University of Ber- 

 lin, as examples of elements undergoing decom- 

 position at ordinary temperatures. In all prob- 

 ability the behavior is not peculiar to heavy 

 radio-active elements, but occurs with other ele- 

 ments in the periodic system at suitable tempera- 

 ture ranges which differ with different elements. 



Through his experiments with liquid and solid 

 hydrogen, Prof. James Dewar has been able to 

 learn much concerning the true relations of that 

 element. Faraday, Dumas, Daniell, Graham, and 

 Andrews thought that if hydrogen could ever 

 be brought into the state of a liquid or solid 

 it would reveal metallic characters; but Prof. 

 Odling, in 1861, pointed out in his Manual of 

 Chemistry that the chlorous relations of hydro- 

 gen were as decided, important, and frequent as 

 its other ones, and expressed the opinion that 

 it was essentially a neutral or intermediate body, 

 and should not be expected to present, in its 

 liquid or solid form, the appearance of a metal. 

 Dumas found analogies between hydrogen and 

 magnesium, and thought that both elements 

 probably had the same atomic volume; and he 

 deduced a density for hydrogen near the value 

 that has been obtained in subsequent experi- 

 ments. Newlands, in 1872, regarded it as the 

 lowest member of the chlorin family; Mendelef 

 placed it with the alkali metals; and Dr. John- 

 stone Stoney classed it with the alkaline earth 

 metals and magnesium. The conclusion of .Prof. 

 Odling has been confirmed by Prof. Dewar's re- 

 searches. In the account of his investigations 

 given in his presidential address before the Brit- 

 ish Association, 1902, Belfast, he cites the case 

 of liquid hydrogen as an excellent illustration of 

 the truth that no theoretical forecast, however 

 apparently justified by analogy, can be finally ac- 

 cepted as true until confirmed by actual experi- 

 ment. As described in this address, liquid hydro- 

 gen is a colorless transparent body. It has a 

 clearly defined surface, is easily seen, drops well, 

 in spite of the fact that its surface tension is 

 only the twenty-fifth part of that of water or 

 one-fifth that of liquid air, and can be poured 

 easily from vessel to vessel. The liquid does not 

 conduct electricity, and. if anything, is slightly 

 dianianetic. Compared with* an equal volume 

 of liquid air, it requires only one-fifth the quan- 



tity of heat for vaporization; on the other hand, 

 its specific heat is ten times that of liquid air or 

 five times that of water. The coefficient of ex- 

 pansion of the fluid is about ten times that of gas. 

 It is by far the lightest liquid known to exist, 

 its density being only one-fourteenth that of 

 water; the lightest liquid previously known was 

 marsh-gas, which is six times heavier. The only 

 solid which has so small a density as to float 

 upon its surface is a piece of pith wood. At ordi- 

 nary atmospheric pressure it boils at 252.5 

 C., or 20.5 absolute. The critical point of the 

 liquid is about 29 absolute, and the critical 

 pressure is not more than 15 atmospheres. The 

 vapor of the hydrogen arising from the liquid 

 has nearly the density of air that is, fourteen 

 times that of the gas at the ordinary tempera- 

 ture. It becomes a solid, resembling frozen foam, 

 at 258 C., and may be got in the form of a 

 clear, transparent ice, melting at about 55 abso- 

 lute, under a pressure of 55 millimeters, and hav- 

 ing one-eleventh the density of water. 



In a lecture on Catalysis, Prof. William Ost- 

 wald defined a catalyst as any substance which 

 will alter the velocity of a chemical reaction 

 without appearing in the final product, and 

 catalysis as the process induced by it. Catalysis 

 is extremely common, and as a matter of fact 

 appears wherever the velocity of a chemical reac- 

 tion can be measured. Catalytic reactions were 

 divided by the author into four groups: 1. Re- 

 lease in supersaturated solutions, as when such 

 solutions of Glauber's salts are crystallized by a 

 small trace of the solid substance with which 

 the solution is saturated. It also appears in so- 

 lutions of gases, vapors, etc. 2. Catalysis in 

 homogeneous solutions the largest and theoret- 

 ically the most important class of contact reac- 

 tions. 3. Heterogeneous catalysis, which is illus- 

 trated in the action of platinum on combustible 

 mixtures of gases, as of oxygen and hydrogen, 

 or in the combustion of sulfur dioxid to tri- 

 oxid. 4. Enzymes, which are to be looked upon 

 as catalysts that are in the organs during the 

 life of the cell, and by the action of which it 

 discharges the greatest part of its duties. There 

 seems to be no kind of chemical reaction which 

 can not be catalytically influenced, no chemical 

 substance, whether element or compound, which 

 can not act catalytically. There are both gen- 

 eral and specific catalysts. Among the theories 

 of catalysis that have been proposed, that of 

 Liebig, that it is the direct consequence of the 

 law of inertia; the hypothesis of molecular vi- 

 brations; and the theory of Euler, that the cata- 

 lytic substance has the property of altering the 

 concentration of the ions were reviewed by the 

 author and found to be inexplicable or insuffi- 

 cient. In the case of the first class of catalyses, 

 however release in supersaturated solutions 

 the theory is known. In all cases there is the 

 formation of a system the stability of which is 

 not the greatest possible under the given condi- 

 tions of temperature and pressure. There are, 

 on the contrary, other more stable conditions 

 which are characterized by the fact that in them 

 a new phase that is. a physically different com- 

 ponent with other properties makes its appear- 

 ance. In supersaturated Glauber's salt this is 

 the solid salt: in supersaturated soda water it i 

 is carbonic-acid gas. 



Experiments on the antiseptic properties of 

 dilute solutions of acids were made by M. Bial 

 on yeast-cells. The retarding action of different 

 acids on the development of the cells was meas- 

 ured by observing the amount of carbon diox- 

 id liberated from a solution of grape-sugar. It 



