The constitution of the atom is one of the chief problems in physical chemistry at the present time, and evidence is accumulating that the atomic weight of an element is not, as was once thought, a natural constant, like the ratio of the circumference of a circle to its diameter, but a quantity which can fluctuate within certain limits. Thus, according to Professor Soddy, radium F, on losing an atom of helium, has its atomic weight reduced from 210 to 206, and then becomes chemically indistinguishable from lead. Thorium C (212), in the same manner, yields another form of lead with the atomic weight 208, and radium C (214) a third form with the atomic weight 210. A species of lead from Ceylon, whose atomic weight is slightly different from that of ordinary lead, lends colour to these assertions, though it cannot be supposed that all the lead in nature is derived from radio-active metals of higher atomic weight.
The subject of catalysis is assuming a greater commercial importance than heretofore, it having been discovered that hydrocarbons are enabled by this means to take up additional atoms of hydrogen, and form oils, while certain oils can be hardened into fats. Thus acetylene can be changed into complex products similar to and even identical with petroleum, and according to Professor Sabatier of Toulouse, it is even possible to imitate the Galician, North American, Rumanian and Caucasian oils at will, by varying the conditions. It is not likely that this will be done on a sufficient scale to compete with these types in the market, though a considerable industry has sprung up of late, founded on a variety of the same process. Oleic acid, for example, can be made to take up two atoms of hydrogen, and becomes converted into stearic acid; fish oils lose their smell and are turned into a hard odourless tallow. In France, the United States, and Germany, large quantities of butter substitutes and lard substitutes are made in this way. The hydrogenation is effected by spraying the oil, and compressing it with hydrogen in the presence of nickel, under suitable degrees of temperature and pressure.
Thoria is a powerful catalyst, and can change organic acids to ketones, while titanium dioxide causes certain of the fatty acids to turn into aldehydes.
At the British Association meeting Professor E. Goldstein gave an address to the chemical section on the influence of the kathode rays on the colour of metallic salts. Sodium chloride is turned brown by this agency; potassium bromide a deep blue; sodium fluoride rose-colour, lithium chloride bright yellow, and so on. The effect is very rapid, and endures for a long time if the salt is kept dark and cold, but disappears more or less quickly under ordinary conditions. It is supposed to be due to decomposition, and both the metal and the acid radicle are concerned in the result. Similar effects have been obtained by Giesel, and also by Kreutz, who found that rock-salt, heated in the vapour of sodium or potassium, also became coloured. The changes so produced are more permanent than those produced by the kathode rays, though if the latter be allowed to act for a sufficiently long time there is less discrepancy in the results. It is interesting to note that ordinary acetic acid shows no colour change, while chloracetic acid is turned yellow, and chloral a bright yellow. Substances so acted on are sometimes phosphorescent, and the effect is due to ultra-violet rays excited by stoppage of the beta and x-rays. The therapeutic effects of kathode and x-ray treatment are no doubt dependent in some degree on these changes, and it may be possible to discover which rays are hurtful, and to cut them off.
The chemical world has been affected by the war in various ways. Thus the supply of potash from Stassfurt has ceased; saccharine, synthetic drugs, and glass apparatus are no longer procurable from Germany, and, most important of all, the dyeing industry is deprived of its mainstay, the aniline colours. With regard to the last, a scheme is under consideration by the Government to establish the manufacture of dyes in this country—which should have been its home after Perkin's discoveries—but the problem is fraught with many difficulties.
Sir James Dewar has recently been studying the composition of air from various sources with reference to rare gases contained in it, and finds that the breath expired by different individuals contains 23-52 parts per million of gases uncondensable at 20° absolute. From 2 to 20 or 30 per cent of this is hydrogen, the amount varying with the time of day and other conditions. In ordinary city air there are, in 1,000,000 parts, about 2.6 of hydrogen, and 22½ of mingled helium and neon; country air contains 22.8 of the former and .5 of the latter. With regard to permeability, helium easily passes through highly heated quartz, a power not possessed by hydrogen, though it passes easily through hot platinum. Oxygen permeates more quickly through a rubber film than hydrogen, and hydrogen than nitrogen. The occlusion of gases, the permeability of metals and the ubiquity of hydrogen add to the difficulty of these investigations, all rubber connections and greased stopcocks having to be discarded.
C. L. B.
Botany.
The year has seen the publication of a considerable amount of research of a detailed and specialised character, but it does not appear to have been marked by contributions of immediate general interest or of outstanding importance.
At the meeting of the British Association in Australia, the Presidential address, by Professor Bower of Glasgow, dealt partly with the history of Australian Botany from Joseph Banks, who sailed with Captain Cook in 1770, to the present day; and partly with special Australian plants on which Bower himself has worked, especially with Phylloglossum, a very primitive Lycopod, and Tmesipteris, a link between living Lycopods and fossils of the group Sphenophyllales; and other primitive Australian forms. Numerous other papers dealt with the Australian flora, etc.