1882.] 



On a Series of Salts, Sfc. 



267 



January 26, 1882. 



THE PRESIDENT in the Chair. 



The Presents received were laid on the table, and thanks ordered 

 for them. 



The following Papers were read : — 



I. " On a Series of Salts of a Base containing Chromium and 

 Urea. No. 1." By W. J. Sell, M.A., F.I.C., Demon- 

 strator of Chemistry in the University of Cambridge. Com- 

 municated by Professor G. D. Liveing, F.R.S. Received 

 January 13, 1882. 



Various compounds of urea with metallic salts and oxides have 

 been described by Werther and Liebig. Some of these are suggestive 

 of an analogy between urea and ammonia, while others seem alto- 

 gether anomalous. The following account of some chromium com- 

 pounds of urea may help to throw some light on the nature of such 

 compounds, for they appear to show that a very definite base is 

 formed by a combination of urea with chromium. 



When powdered and carefully dried urea is moistened with chromyl 

 dichloride, and the mixture vigorously shaken, the temperature rises 

 considerably, and on treating the resulting mass with water, there 

 remains undissolved, a green crystalline powder. The nature of the 

 green salt thus obtained is at present under investigation. It is 

 insoluble in alcohol, ether, and chloroform. It dissolves in hot water 

 with decomposition, another salt separating out as the liquid cools in 

 brilliant olive-green needles, which by a second crystallisation is 

 obtained in a pure state. The examination of this body showed it to 

 be the dichromate of a base containing the elements of urea and 

 chromium, and to have the formula 



{(CON 3 H 4 ) 12 Cr 2 }(Cr 3 7 ) 3 3H 2 0. 



The dichromate thus obtained is sparingly soluble in cold, more 

 freely in hot water, and is decomposed by boiling the solution. Its 

 aqueous solution gives green crystalline precipitates with platinic 

 chloride and potassium ferrocyanicle, but none with ammonia. 

 The following results were obtained on analysis : — 

 The numbers given refer to the dried salt, unless expressly stated 

 to the contrary. 



