Chemistry and Physics. 553 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. Boiling-points of Metals. — Our data in regard to the boiling- 

 points of most of the common metals have been very uncertain 

 and discordant, but H. C. Greenwood has recently made an 

 extended investigation of this subject, and has succeeded in 

 determining a number of these constants with a fair degree of 

 approximation. He employed a slender graphite crucible placed 

 in a slightly larger vertical carbon tube which was heated by 

 electrical resistance. The temperature was measured by observa- 

 tion of the walls of the crucible through a horizontal tube con- 

 nected with the carbon tube, by means of a Wanner optical 

 pyrometer. The surface of the metal was observed through a 

 window at the top of the apparatus, and its agitation indicated 

 the boiling-point. A current of hydrogen was passed in at the 

 side tube, as a protection to the crucible. It was found that the 

 boiling-points were lower in the presence of a current of hydrogen 

 than in the case where nitrogen was used, apparently on account 

 of the fact that hydrogen easily penetrated the walls of the hot 

 crucible and carried off or diluted the column of heavy vapor 

 above the metal. In the cases of the metals which form carbides, 

 the interior of the crucible was coated with magnesia in such a 

 manner that practically no carbide was produced. When this pre- 

 caution was not taken, boiling-points several hundred degrees too 

 high were obtained in some cases. The following table gives the 

 results as the approximate boiling-points of eleven metals : 



Aluminium 1800° C. Lead 1525° C. 



Antimony 1440 Magnesium 1120 



Bismuth 1420 Manganese 1900 



Chromium 2200 Silver 1955 



Copper 2310 Tin 2270 



Iron 2450 



— Chem. JVews, c, 39, 49. h. l. w. 



2. Sodium Alum. — This alum, NaAl(S0 4 ) 2 .12H 2 0, was made by 

 several of the earlier investigators, but its existence has been 

 questioned several times. For instance, Ostwald in his "Principles 

 of Inorganic Chemistry" states that sodium and lithium do not 

 form alums. W. P. Smith has now shown conclusively that the 

 sodium alum may be easily prepared in well-developed crystals 

 of the usual octahedral form, but he has shown also that it does 

 not exist at temperatures much above 30° C. Above this tempera- 

 ture the separate salts crystallize side by side, and when the alum 

 in contact with its saturated mother liquor is heated to the higher 

 temperature it is decomposed into an opaque, finely divided mass. 

 Jour. Amer. Chem. tioc, xxxi, 245. h. l. w. 



