186 Scientific Intelligence. 



culty was encountered in purifying the gas, and the results 

 varied to a considerable extent. The following table gives 

 examples of the amounts of emanation in equilibrium with 1 g. 

 of radium : 



At the beginning At the end 



of the experiment of the experiment 



J.32C mm Q.gQCmm 



0-80 " 



0-97 " 0-66 " 



1-05 " 0-58 " 



These results, considering the difficulties encountered, agree 

 fairly well with the volume, 0'b^ cmm , which Rutherford has cal- 

 culated theoretically, and the lowest result is only one-ninth of 

 the volume, H i'0*l cmm , found by Ramsay and Cameron some time 

 ago. The gas underwent remarkable changes in volume after it 

 was collected. In some instances it contracted to less than half 

 its volume in the course of several hours, and then showed little 

 change in the course of a week. In other cases an increase in 

 volume was shown to double that of the original gas, and then a 

 slow contraction followed. » These changes in volume, in many 

 cases, bear no relation to the changes in volume of the emanation 

 itself, for the true volume of the emanation was often only 20 

 per cent of the total gas volume. The author finds no satisfac- 

 tory explanation for these remarkable changes in volume. — 

 Monatshefte, xxix, 995. h. l. w. 



3. A New Method for Separating Tangstic and Silicic Oxides — 

 Defacqz treats the mixed acids in a boat at a red heat with a 

 current of hydrogen until the tungsten is completely reduced to 

 a lower oxide or to the metal. Then the boat is heated in a tube, 

 so arranged as to collect the volatile products, in a current of 

 perfectly dry chlorine gas. If air is absent the whole of the 

 tungsten is volatilized as hexachloride and oxychloride. The 

 volatile products are collected by means of ammoniacal water 

 and the tungsten is determined by one of the usual methods. The 

 silica in the boat is weighed after heating it in hydrogen again to 

 make sure, by the absence of any blackening, that the separation 

 is complete. — Bulletin, IV, iii, 892. h. l. w. 



4. A Silicide of Uranium. — Defacqz has prepared the com- 

 pound Si 2 U by the aluminothermic method, using finely divided 

 aluminium, flowers of sulphur, silica, and uranium oxide in proper 

 proportions. The silicide forms a brilliant crystalline powder 

 with metallic luster. It is interesting to notice that the author 

 has prepared in the same way analogous silicides of molybdenum 

 and tungsten, Si 2 Mo and Si 2 W, and that these silicides all corre- 

 spond in type to the silicides of the iron group of metals having 

 the general formula Si 2 M. — Comptes Hendus, cxlvii, 1050. 



h. l. w. 



5. A New Periodic Function of the Atomic Weight. — Viktor 

 Poschl takes the percentage composition of the earth's crust as 



