Chemistry and Physics. 475 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. The Peculiarity of Nickel and Cobalt Sulphides. — The 

 contradictory behavior of these sulphides in the fact that they 

 are not formed in solutions of strong acids and that when once 

 formed they are practically insoluble in strong acid solutions is 

 well known to every student of analytical chemistry, as it is 

 contrary to an almost universal rule governing precipitation. A. 

 Thiel and H. Gessner have made an elaborate study of this 

 matter by precipitating nickel sulphide under various conditions, 

 treating the rjrecipitates with acids for varying lengths of time, 

 repeating the treatment with the undissolved residues and deter- 

 mining quantitatively the amounts of nickel dissolved. They 

 believe that they have explained the contradictory behavior of 

 nickel sulphide in its essential features, for they find that an 

 easily soluble nickel sulphide exists, but that it undergoes a 

 spontaneous modification into more difficultly soluble sulphide, 

 probably on account of polymerization. It is their opinion that 

 besides the soluble sulphide, which they designate as the 

 a-modification, two other modifications, /? and y, exist. They 

 consider it highly improbable that the soluble form, the a-NiS, is 

 a hydrate as has been surmised. They find that all the modifica- 

 tions have the same empirical composition, corresponding to NiS, 

 and on this account they believe that polymerization takes place. 

 — Zeitschr. anorgan. Chem., lxxxvi, 1. h. l. w. 



2. The Dimethyl Phos£>hates of the Pare Earths.— In connec- 

 tion with the important rare earth investigations that are being 

 carried on at New Hampshire College by Professor James, J. C. 

 Morgan and C. James have prepared the dimethyl phosphates of 

 a number of rare earths and have studied their solubilities with 

 the following results : 



Parts of salt per 100 

 Element Parts of water at 25° 



Lanthanum 103*7 



Cerium 79-6 



Praseodymium . 64*1 



Neodymium . 56'1 



Samarium 35 - 2 



Gadolinium 23-0 



Yttrium 28 



Erbium ... 1-78 



Ytterbium . _ 1*2 



They have applied these salts to the fractional separation of 

 several mixtures of the earths, and find that the rate of separation 

 is vastly greater than practically all the methods given up to the 

 present time. Lanthanum, cerium, praseodymium and neodymium 



