78 



CHEMISTRY. 



ence of asymmetrical carbon, and Le Bel has 

 recently prepared optically active nitrogen com- 

 pounds containing an asymmetrical nitrogen 

 atom. Van 't Hoff's discovery of the identity of 

 the laws of gases with those of dissolved sub- 

 stances is to be characterized as the greatest step 

 forward which has been made in this direction. 

 If we reflect that the development of the molec- 

 ular idea is most decidedly based npon the laws 

 of the gases in their simple form, we recognize 

 at once that all the important relations which 

 have here been found can be directly transferred 

 to the domain of solution. The latter has, how- 

 ever, at the same time, far more varied possi- 

 bilities in the form of its phenomena. This dis- 

 covery has been of great value in the study and 

 enlargement of the theory of molecular weight. 

 Another aid to investigation, " of unexampled 

 sweep and value," has been found in the theory 

 of electrolytic dissociation of Arrhenius. In this 

 theory, in the aqueous solutions of the electro- 

 lytes, the salts, acids, and bases, a greater or less 

 proportion of the dissolved molecules are regarded 

 as split up into electrically charged constituents or 

 ions, which exist in the solution independently of 

 one another in the same manner as the partial mol- 

 ecules of a dissociated gas. If in the field covered 

 by Arrhenius the question be one of dissociation, 

 and the laws of gases do, according to Van 't 

 Hoff, hold for dissolved substances, it follows 

 that the entire theory of the chemical affinity of 

 electrolytes must be yielded by the application of 

 those laws of dissociation. " This means nothing 

 less," says Prof. Ostwald, " than that the problem 

 of chemical affinity is in reality solved." 



Chemical Physics. According to the re- 

 searches of P. Mylius and F. Poerster, supported 

 by the observations of Pfeiffer and Kohlrausch, 

 the solution of glass in water depends on a decom- 

 position in which, first, free alkali appears. The 

 silica of the glass is secondarily dissolved by the 

 free alkali, the constituents of the solution vary- 

 ing according to the conditions of digestion. 

 The susceptibility of glass to attack under given 

 conditions is measured by the quantity of alkali 

 which passes into solution from a given surface 

 under those conditions. It increases with a ris- 

 ing temperature, is decreased by a previous treat- 

 ment with water, and is modified by " weather- 

 ing." Different sorts of glass display a different 

 persistence of the solution. Prom glasses of 

 equal susceptibility to attack unequal weights 

 may pass into the solution. After treatment 

 with water, surfaces of glass have the property 

 of taking up alkali from the solutions which 

 have been formed and of giving it up again on 

 renewed treatment with water. Potash glasses 

 are much more soluble than soda glasses, but 

 the differences disappear in proportion as the 

 glass is richer in lime. In the substance of glass 

 vessels which are not readily attacked by cold 

 and hot water, the lime, alkalies, and silica must 

 bear a certain proportion to each other. Among 

 the best-known glasses plumbiferous flint glass 

 is least soluble in water, but it is corroded at 

 the surface and easily decomposed by acids. 



An experiment by W. Spring indicates the 

 possibility of certain metals existing in the gase- 

 ous state at temperatures below their melting 

 point. Leaflets of silver, platinum, and gold 

 were heated to 150 C. with concentrated hydro- 



chloric acid in sealed tubes. The metals were 

 dissolved and the chlorides formed were re- 

 duced by the hydrogen evolved from the metals 

 and the hydrochloric acid. They were deposited 

 on the sides of the tubes in microscopic crystals. 

 It may be assumed that in this experiment even 

 the platinum existed for some time as a liquid 

 before taking a crystalline form. 



The theory of Berzelius that the spontaneous 

 ignition of coal is promoted by the gradual oxi- 

 dation of the pyrites it contains is disputed by 

 Prof. Vivian B. Lewes, who, comparing the igni- 

 tion temperatures from 698 F. to 870-5 P. of 

 different kinds of coal, assumes that such de- 

 grees of heat could not be produced by that pro- 

 cess in the small trace of pyrites scattered 

 through a large mass of coal. The author be- 

 lieves that the true cause of combustion is 

 found in the power of coal to attract and con- 

 dense gases upon its surface a power which in- 

 creases in proportion to the fineness with which 

 the coal is broken up and the total area of sur- 

 face expanded. Freshly powdered charcoal ig- 

 nites readily. The readiness of coal to ignite 

 increases also with the temperature of the stor- 

 age room. The tendency or power of the coal to 

 absorb oxygen is therefore to be taken as the 

 true index of the danger of ignition. This may 

 be roughly gauged by the amount of moisture 

 which the coal can absorb from the air ; for if 

 much moisture is found in an air-dried sample 

 of coal it stamps it at once as a highly absorbent 

 form, which must on that account be stored 

 with special precautions, while if little moisture 

 be present the sample is probably unable to take 

 up enough oxygen to lead to serious mischief. 

 When once a coal has taken up oxygen and the 

 early stages of heating are passed and the tem- 

 perature has again fallen, all danger of ignition 

 is over, and the coal may be stored in any quan- 

 tity with safety ; so that if it were practicable 

 to keep newly mined coal for a month in moder- 

 ate-sized heaps, and then to avoid much break- 

 age in afterward loading it, spontaneous ignition 

 would be almost unknown. 



The point at which sulphur ignites has not 

 been satisfactorily determined and has been con- 

 sidered variable. Some authors suppose, from 

 the ease with which sulphur has been observed 

 sometimes to take fire, that it is low ; some that 

 allotropic conditions influence it. Prof. W. R. 

 Hodgkinson believes that allotropic conditions 

 have little or no effect, and that sulphur ignites 

 only after it has reached the gaseous state. 

 From the fact that the vapor of boiling sulphur 

 at 448 C. may escape into the air without igni- 

 tion, and from other circumstances, he is of the 

 opinion that the element does not ignite at a 

 lower temperature than 300 C. An experiment 

 by Bertram Blount led him to a similar conclu- 

 sion, but he has revised his opinion in the light 

 of a more accurate experiment by J. Rutherford 

 Hill, which gives the igniting point of sulphur 

 as 248 C. ' 



A study of the effect of minute percentages of 

 foreign elements on the mechanical properties 

 of gold disclosed to Prof. W. C. Roberts- Austen 

 a relation between the results obtained and the 

 position in the periodic table of the introduced 

 elements, and he predicted a similar phenome- 

 non in the case of iron. The prediction has 



