Chemistry and Physics. 99 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. The S2nntharisco2ye. — In connection with a discussion of 

 certain properties of radium emanations, Sir William Crookes 

 describes a striking phenomenon produced upon the zinc sulphide 

 screen by the heavier, non-deflectable, positive atoms emitted by 

 radium. He says : " If a solid piece of radium nitrate is brought 

 near the screen, and the surface examined with a pocket lens 

 magnifying about 20 diameters, scintillating spots are seen to be 

 sparsely scattered over the surface. On bringing the radium 

 nearer the screen the scintillations become more numerous and 

 brighter, until when close together the flashes follow each other 

 so quickly that the surface looks like a turbulent, luminous sea. 

 It seems probable that in these phenomena we are actually wit- 

 nessing the bombardment of the screen by the positive atoms 

 hurled off by radium with a velocity of the order of that of light : 

 each scintillation rendering visible an impact on the screen, and 

 becoming apparent only by the enormous extent of lateral dis- 

 turbance produced by its impact. Just as individual drops of 

 rain falling on a still pool are not seen as such, but by reason of 

 the splash they make on impact and the waves they produce in 

 ever widening circles." 



The spinthariscope, devised for observing this phenomenon, 

 consists of a brass tube with a blende screen at one end of it 

 which has a speck of radium salt in front of it and about a milli- 

 meter off, and a lens at the other end which can be accurately 

 focussed upon the screen. — Chem. JVeivs, Ixxxvii, 241. h. l. w. 



2. Pro2Jerties of Sodium Sulphate Solutions. — It is well known 

 that sodium sulphate with ten molecules of water of crystalliza- 

 tion is deposited from solutions below 32*38°, while the anhydrous 

 compound is formed at higher temperatures. No evidence has 

 beAi obtained heretofore that water combines with sodium sul- 

 phate while the latter is in solution. Marie and Marquis have, 

 therefore, undertaken the investigation of this question by a new 

 method. They determined the solubility of sodium chloride in a 

 given solution of sodium sulphate at temperatures varying from 

 14-8° to 34*28°. It was expected that a sudden change in the 

 solubility would occur if at some point the sodium sulphate mole- 

 cules formed a combination with water. No such sudden change 

 was observed, for the results when plotted gave a perfectly regu- 

 lar curve. Consequently, there is no reason for supposing that 

 the salt with ten molecules of water exists in solution. — Comptes 

 Mendus, cxxxvi, 684. h. l. w. 



3. Radio-active Lead. — About two years ago Hofmann and 

 Strauss announced the preparation of radio-active salts from the 

 lead obtained by the usual chemical methods from various min- 

 erals containing uranium and thorium. Hofmann and Wolfl 



