2^8 



NA TURE 



[July i6, 1896 



Fig. 7. - Gold 90 pans, 



This shows Ihat there is still a tendency in this gcild alloy witli 

 10 per cent, of zinc to lieconie enriched towards the centre. 



. It. — Gold 63 parts, silver 

 7 parts, lead 20 parts, zinc 



Very marked separation take.s place here, the difference at 



various points of the sphere being very remarkable, and forcibly 



illustrating the difficulties to which reference is made at the 



commencement of this paper. 



As, however, it appears, that when a certain amount of silver 



is present, the irregularity in composition disappears, this 



mixture of — 



Zinc... ... ... ... ... ... 10 



Lead ... ... .. 20 



Silver ... ... 7 



Gold 63 



was alloyed with more silver, so that it contained 15 percent. 



of silver (nearly half the united amounts of zinc and lead present 



in the alloy). 

 This, cast into the 3-in. spherical mould, showed the following 



results at the points indicated. In appearance, the metal, when 



sawn in two, was homogeneous. 



-.\lloyed s 



r ; weight 3*450 kilograms. 



There is here still evidence of liquation of gold towards the 

 centre, but comparison of Kig. 12 with that which immediately 



NO. 1394, VOL. 54] 



precedes it will show how greatly the arrangement of the alloy 

 has been modified by the presence of the additional 8 ])er cent, 

 of silver. The proportion of silver in this alloy was proved by- 

 assay to be I5'5 per cent. 



As there was still evidence of liquation, the metal was cast 

 with still more silver, making 20 per cent, of silver in all. The 

 alloy, when cast into a mould, proved to be almost uniform in 

 composition, the difference between the centre and the extreme 

 portions being .very slight. 



Liquation had practically ceased, a fact which proves in- 

 contestably that silver is the solvent for the base metals, zinc, 

 and lead, when they are alloyed with gold. 



Coiiiliisioiis. — (i) Alloys of gold with base metals, notably 

 with lead and zinc, now often met with in industry, have 

 the gold concentrated towards the centre and lower portions, 

 which renders it impossible to ascertain their true value with 

 even an approximation to accuracy. 



(2) When silver is also present these irregularities are greatly 

 modified. 



The method of obtaining "cooling-curves" of the alloys 

 shows that the freezing points are very different when silver is 

 present in the alloy and when it is absent from it. 



(3) This fact naturally leads to the belief that if the base 

 metal present does not exceed 30 per cent., silver will dissolve it 

 and form a uniform alloy with gold. 



(4) This conclusion is sustained by the experiments illustrated 

 by Figs. 9, II and 12, which, in fact gradually lead up to it, 

 and enable a question of much interest to be solved. 



Edward Matthey. 



THE ATOMIC WEIGHT OF OXYGENS 

 n^HIS monograph embraces a complete collection of the 

 results obtained by Dr. Morley while working on this 

 subject, and gives a detailed account of the various apparatus 

 used. The experiments described extended o\er a very lengthened 

 period. They consisted of the determination of the ratio be- 

 tween oxygen and hydrogen by two distinct methods, viz. by 

 actually weighing the gases and by synthetising water. In all 

 his experiments Dr. Morley dealt with far larger volumes of 

 purer gases than previous experimenters had used, and in weigh- 

 ing them he reduced with surprising completeness every possible 

 .source of error. In his work on the synthesis of water. Dr. 

 Morley succeeded in weighing the hydrogen and oxygen burned, 

 and also the water produced thereby, achieving an exactness 

 not attained by any previous experimenter, as none before had 

 weighed all three factors. All experiments dealing quanti- 

 tatively with gases are naturally extremely difficult, but Dr. 

 Morley has, by paying attention to every detail, brought each 

 process to a great pitch of accuracy. 



The major corrections that were introduced into the deter- 

 minations were as follows. 



(i) The expansion of the glass of the globes. 



(2) The errors of the mercurial thermometers. 



(3) The deviation of the mercurial from the hydrogen thermo- 

 meter. 



(4) The difference between the coefficients of expansion of 

 oxygen and hydrogen. 



(5) The elevation of the cistern of the barometer above the 

 centre of the globe when reading pressure. 



(6) The correction of the scale of the barometer. 



(7) The force of gravity at the laboratory. 



In weighing the gases Dr. Morley employed large glass globes 

 varying in capacity from nine to twenty-one litres. All data 

 connected with the capacity of these were accurately determined. 

 As the globes were so large it was found impossible to weigh 

 them full of water to measure their capacity, and a difl'erent 

 method had to be adopted. The globes were first weighed in 

 air, then sunk in water, the weights being determined to keep 

 the globes immersed ; lastly the globes were filled with water, 

 and again weighed in water. From these were obtained the 

 external volume, the solid contents, and the capacity within '02 

 per cent. In introducing a correction for the compression of 

 the globes when exhausted. Dr. Morley devised an exceedingly 

 ingenious plan. The compression itself was determined by 

 placing the globe in a copper cylinder, which was then closed 



1 " On the Densities of Oxygen and Hydrogen, and on the Ratios of 

 their Atomic Weights," by Dr. E. W. Morley. Smithsonian Contributions 

 to Kno7ulettge, No. 980. (Washington, 1895.) 



