230 Scientific Intelligence. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. On the Lowering of the Freezing point of Metals by the 

 addition of other Metals. — Heycock and Neville have investi- 

 gated the lowering of the solidifying point of a metal which takes 

 place when a small quantity of another metal is dissolved in it 

 in the liquid state. In the first experiments, a number of units 

 of mass corresponding to the atomic mass of each of several 

 metals was dissolved in one hundred atomic masses (11800 units 

 of mass) of melted tin, and the temperature of solidification 

 noted. The difference between this and the solidifying point of 

 the pure metal is called the atomic fall. For Na, this was found 

 to be 2-5° ; for Al 1'34 ; for Cu 2*47 . for Zn 2*53 ; for Ag 2-67 ; 

 for Cd 2-16 ; for Sb a rise of 2-3 ; for Au 2 '80 ; for Hg 2 -3 ; for 

 Tl 2-6 ; for Pb 2*6; and for Bi 2-10. The next series of experi- 

 ments was made with sodium as the solvent ; a cylinder of cast 

 iron 6 to 8 inches high and 5 inches in diameter being used, in 

 the axis of which was a hole 1 to 2 inches in diameter and 4 

 inches deep, within which worked an annular stirrer. This 

 cylinder was heated by a gas burner, being wrapped with 

 asbestus cloth so that it cooled at the rate of only a degree 

 in two minutes. The temperatures were noted on a thermom- 

 eter having an arbitrary millimeter scale and reading to nearly 

 one-hundreth of a degree. From 20 to 30 grams of sodium 

 were* melted in this .cylinder and covered with a layer of par- 

 affin. The whole was then raised to the boiling point of 

 the paraffin, the metal added in the state of fine division, the 

 mixture well stirred and the whole allowed to cool. The ther- 

 mometer fell steadily to a certain point, then rose suddenly 

 through one or two degrees where it remained stationary for sev- 

 eral seconds, sometimes a minute. The highest temperature 

 reached during this surfusion was taken to be the freezing tem- 

 perature of the alloy. The first point noted was that sodium 

 even at 250° dissolved only a few metals ; Au, Li, K, Hg, Tl 

 and In dissolving freely, Pb and Cd sparingly, while Zn, Sn, Al, 

 Mg, Ag, Pt and Fe did not dissolve in appreciable quantities. 

 On placing a clean piece of the sodium alloy in absolute alcohol, 

 the dissolved metal separated as a fine powder generally crys- 

 talline. In the case of gold, 100 atomic units of mass of sodium 

 were found to keep in solution 3*5 atomic units of mass of this 

 metal, forming a saturated solution behaving like a weak solution 

 of sodium chloride in water as observed by Guthrie. The atomic 

 fall per atomic mass-unit for this alloy was 4-578°, the tempera- 

 ture of solidification being remarkably constant at 81*92°. On 

 treating with alcohol the gold separates in fine needles. An alloy 

 obtained by diluting this saturated alloy with sodium, gave on 

 analysis gold 15, sodium 85*03 per cent and had a density of 

 1*152; the calculated density being 1*141. Thus showing that 

 the density of the alloy is a mean of that of its constituents and 



