ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 557 



alloys contain the same constituents that occur in the tin-antimony 

 system, with the addition of lead ; lead acts merely as a solvent. The 

 microstructnre of some of the alloys showed that complete equilibrium 

 had not been obtained in the cooling. 



Gold Tellurides* — G. Pellini and E. Quercigh have determined the 

 equilibrium diagram of the gold-tellurium system by thermal methods. 

 A single maximum in the curve, at 404° C, corresponds with the com- 

 pound AuTe 2 . This compound occurs in nature as calaverite. 



Amalgams containing Silver and Tin.f — R. A. Joyner has investi- 

 gated the ternary system tin-silver-mercury, studying more especially the 

 peculiarities of the alloys used as dental amalgams. Fresh tilings of 

 silver-tin alloys require more mercury for amalgamation than filings 

 which have been kept for some months, or heated to 100° C. This 

 property of " ageing " is shown to be a characteristic of the compound 

 Ag 3 Sn ; possibly " ageing " is the result of the polymerization of this 

 compound. The reaction, to which is due the hardening of amalgam 

 prepared by mixing filings of silver-tin alloy with mercury, is the breaking 

 up of Ag 3 Sn with the formation of Ag 3 Hg 4 and free tin. The ternary 

 equilibrium was studied chiefly by the method of chemical analysis of 

 the liquid phase, separated from the alloy by mechanical means. 



Occlusion of Hydrogen by Palladium-gold Alloys.! — A. J. Berry 

 has determined the amount of hydrogen occluded by a number of 

 palladium-gold alloys. Two similar voltameters containing dilute sul- 

 phuric acid were connected together in series. Both anodes and one 

 cathode were of platinum ; the other cathode was of the alloy under 

 investigation. The difference between the volumes of hydrogen col- 

 lected from the two cathodes is the amount occluded by the palladium- 

 gold cathode. Alloys containing less than 25 p.c. palladium do not 

 occlude hydrogen, while the occluding power of alloys containing more 

 than 25 p.c. is a simple function of the concentration of palladium. 



Properties of Cast and Rolled Gold Plate.§ — H. J. Morris and 

 A. McWilliam have investigated the relative strengths of cast and of 

 swaged dental gold plate. Static bending tests indicated that cast plate 

 had a much lower elastic limit than rolled or soldered plate, and in 

 repeated alternating bending tests the endurance of the cast plate was 

 very low. Some notes on the microstrncture and the fractures of the 

 different plates are given. 



Flow-pressure of Tin.|] — The pressure at which a plastic metal will 

 Mow steadily through an aperture appears to be an important physical 

 constant of the metal. E. Janecke has measured the flow-pressure of 

 tin at different temperatures up to 217° C. The curves showing the 

 relation between temperature and flow-pressure do not indicate by any 

 inflection the temperature at which the allotropic change in tin takes 

 place. 



* Atti R. Accad. Lincei, xix. (1910) pp. 445-9, through Journ. Chein. Soc, 

 c. (1911) p. 45. 



t Journ. Chem. Soc, xcix. (1911) pp. 195-208 (2 figs.). 

 X Journ. Chem. Soc, xcix. (1911) pp. 463-6 (1 fig.). 



§ Proc Roy. Soc Medicine (Odontological Section) iv. (1911) pp. 57-6S (9 figs.). 

 Metallurgie, viii. (1911) pp. 68-72 (12 figs.). 



Aug. 16th, 1911 2 o 



