84 



NATURE 



[Nov. 2 2, 1888 



of " traces " upon masses, and the authority of Berthollet 

 was not sufficient to save them from neglect. In this 

 eventful year for science, 1803, the latter published his 

 ess-iy on chemical statics, in which he stated, as a funda- 

 mental proposition, that in comparing the action of bodies 

 on each other, which depends " upon their affinities and 

 mutual proportions, the mass of each has to be con- 

 sidered " (English edition, by M Farrell, M.D., 1804, p. 5). 

 His views were successfully contested by Proust, but, as 

 Lothar Meyer says, the influence on chemistry of the re- 

 jection of Berthollet's views was remarkable: — "All 

 phenomena which could not be attributed to fixed atomic 

 proportions were set aside as not truly chemical, and were 

 neglected. Thus chemists forsook the bridge by which 

 Berthollet had sought to unite the sister sciences, physics 

 and chemistry." Fortunately, however, in this country 

 there was one chemist who had followed up the line of 

 work indicated by the early metallurgists, for in 1803, the 

 same year as that in which both Berthollet's essay and 

 Dalton's atomic theory were published, Charles Hatchett 

 (Phil. Trans., vol. xciii. p. 43, 1803) communicated to the 

 Royal Society the results of a research which he had con- 

 ducted, with the assistance of Cavendish, in order to ascer- 

 tain " the chemical effects produced on gold by different 

 metallic substances when employed in certain " (often very 

 small) " proportions as alloys." 



Allusion was then made to the evidence of the passage 

 of metals into allotropic states, and it was shown that, 

 although the importance of the isomeric and allotropic 

 states was abundantly recognized in organic chemistry, it 

 had been much neglected in the case of metals. Special 

 attention was then devoted to the works of Joule and 

 Lyon Playfair, who showed, in 1846, that metals in dif- 

 ferent allotropic states possessed different atomic volumes, 

 and the lecturer then proceeded to the consideration of the 

 work of Matthiessen, who, in i860, was led to the view 

 that in certain cases when metals were alloyed they passed 

 into allotropic states, probably the most important gene- 

 ralization which has as yet been made in connection 

 with the molecular constitution of alloys 



Instances of allotropy in pure metals were then shown 

 to the audience, such, for example, as Bolley's lead, which 

 oxidizes readily in air ; Schiitzenberger's copper ; Fritsche's 

 tin, which fell to powder when exposed to an exceptionally 

 cold winter ; Gore's antimony ; Graham's palladium ; and 

 allotropic nickel. It was further shown that metals could 

 be obtained in chemically active states under the following 

 conditions : — Joule proved that when iron is released from 

 its amalgam by distilling away the mercury the metallic 

 iron takes fire on exposure to air, and is therefore clearly 

 different from ordinary iron, and is, in fact, an allotropic 

 form of iron. Moissan {Comptes re?tdus, vol. Ixxxviii. p. 

 180, 1879) has shown that similar effects are produced in 

 the case of chromium and manganese, cobalt, and nickel, 

 when released from their amalgams with mercury. 



Evidence is not wanting of allotropy in metals released 

 from solid alloys, as well as from fluid amalgams with 

 mercury. Certain alloys may be viewed as solidified 

 solutions, and when such bodies are treated with a suitable 

 solvent, usually an acid, it often happens that one con- 

 stituent metal is dissolved, and the other released in an 

 insoluble form. Reference was then made to a new alloy 

 of potassium and gold, containing about 10 per cent, of 

 the precious metal. If a fragment of this alloy be thrown 

 upon water, the potassium takes fire, decomposes the 

 water, and the gold is released as a black powder : there 

 is a form of this black or dark-brown gold which appears 

 to be an allotropic modification of gold, as it combines with 

 water to form auric hydride. If this dark gold be heated 

 to dull redness, it readily assumes the ordinary golden 

 colour. The Japanese use this gold, released from gold- 

 copper alloys, in a remarkable way, for they produce, by 

 the aid of certain pickling solutions, a beautiful patina on 

 copper which contains only 2 per cent, of gold, while 



even a trace of the latter metal is sufficient to alter the 

 tint of the patina. 



With regard to theoretical views as to molecular change 

 in metals, special care was given to a description of the 

 work of Prof W. Spring, of Lidge, who had furnished 

 much evidence in support of the view that polymerization 

 of metals — that is, the rearrangement of atoms in their 

 molecules— could take place even in solid alloys of lead 

 and tin. 



With reference to the passage of metals into allotropic 

 states under slight external influences, it was stated that 

 Debray {Comptes rendus, vol. xc p. 1 195, 1880) has given a 

 case of an alloy in which a simple elevation of temperature 

 induces allotropic change in the constituent metals. It is 

 prepared as follows : 95 parts of zinc are alloyed by fusion 

 with 5 parts of rhodium, and the alloy is treated with 

 hydrochloric acid, which dissolves away the bulk of the 

 zinc, leaving a rich rhodium-zinc alloy, containing about 

 80 per cent, of rhodium. When this alloy is heated in 

 vacuo to a temperature of 400"" C.,a slight explosion takes 

 place, but no gas is evolved, and the alloy is then insoluble 

 in aqua regia, which dissolved it readily before the eleva- 

 tion of temperature caused it to change its state. We are 

 thus presented (as the experiment shown to the audience 

 proved) with another undoubted case of isomerism in 

 alloys, the unstable, soluble modification of the alloy being 

 capable of passing into the insoluble form by a compara- 

 tively slight elevation of temperature. 



The industrial importance of the passage of metals and 

 alloys into allotropic states, and the possibility of changing 

 the mechanical properties of metals by apparently slight 

 influences, were fully dealt with ; and the lecture concluded 

 with a detailed description of Prof Austen's own experi- 

 ments, which have since been printed in the Philosophical 

 Transactions of the Royal Society, the results showing 

 that very small amounts of metallic impurities exert an 

 extraordinary effect on the tenacity and extensibility of 

 gold, and that small as the amounts of these impurities 

 are, their influence is rigidly controlled by the periodic 

 law of Newlands and Mendelejeff, the deleterious action 

 of a metallic impurity being in direct relation to its atomic 

 volume. The audience was asked " to remember that the 

 knowledge of the kind of facts which had been considered 

 comes to us from very early times, for the influence pro- 

 duced on metals by small quantities of added matter had 

 a remarkable effect on the development of chemistry, 

 mainly by sustaining the belief of the early chemists in 

 the possibility of ennobling a base metal so as to trans- 

 mute it into gold. This was the object to which they 

 devoted life and health, and laboured with fast and vigil. 

 We inherit the results of their labours, and their prayers 

 have been answered in a way they little anticipated, for, 

 from an industrial point of view, if not from a scientific 

 one, metals are ' transmuted ' by traces of impurity. 

 Possibly we are nearing an explanation of the causes 

 which are at work,, but the fact remains that iron may be 

 changed from a plastic material, which in ornament can 

 be fashioned into the most dainty lines of flow, into one 

 of great endurance, to which, for the present at least, the 

 defence of the country may be trusted, apparently because 

 armour-plates and missiles owe their respective qualities 

 to the fact that carbon, manganese, and chromium have 

 small atomic volumes." 



THE LEONID METEOR-SHOWER, 1888. 



AT Bristol rain fell heavily between midday on Novem- 

 ber 12 and the same time on November 13, a 5- 

 inch gauge registering an inch and eight-tenths, which is 

 by far the greatest downpour of the year within twenty- 

 four hours. In the afternoon of November 13 the clouds 

 broke, and the weather showed a disposition to become 

 more favourable. At night the sky was moderately clear 



