1882.] of a Base containing Chromium and Urea. 273 



The Nitrate. 



This compound is readily obtained from the dichromate or chloride 

 by nitrate of silver. If the solutions used are warm and fairly con- 

 centrated, a good crop of crystals is deposited on cooling after filtra- 

 tion. The salt separates from the warm saturated solution, or by spon- 

 taneous evaporation in large, well-defined, dark green prisms, which 

 are anhydrous, and may be represented by the formula (C01tf 2 H 4 ) 12 

 Cr 2 (N0 3 ) 6 . The following determinations were made : — 



1. "449 grm. crystallised salt lost no appreciable quantity of water 

 at 104° C, and is therefore anhydrous. 



2. *0908 grm. gave 25*67 cub. centims. nitrogen at 0° and 760 millims. 



3. -378 grm. ignited left '0493 Cr 2 3 . 



4. -22175 „ -02895 „ 



Theory. 



Analysis. 



Percencage. 



C 12 144 



H 48 48 



N 30 420 35-09 



O 30 480 



Cr„ 104-8 8-75 



1196 8 



2. 



3. 



4. 



35 -46 



8-94 



8-95 



The Hydroxide. 



A mixture of the dichromate, cold water, and a slight excess of 

 pure precipitated lead hydroxide, rubbed together in a mortar, the 

 lead chromate removed by filtration and any excess of lead by a drop 

 of the dichromate, yields a bright green strongly alkaline solution. 

 This solution appears to contain the hydroxide of the same base as the 

 salts just described, for they are easily obtained from it by suitable 

 reagents. A precisely similar solution may be obtained from the 

 sulphate by means of barium hydroxide. The compound, however, is 

 slowly decomposed in the cold, more rapidly on heating, the solution 

 losing its alkalinity, chromic hydroxide separating out and urea 

 remaining in solution. If the green aqueous solution be mixed with 

 alcohol, most of the hydroxide is deposited as a light green precipitate, 

 which may be collected, redissolved in water, and reprecipitated by 

 alcohol unchanged. It is, however, difficult to prevent some decom- 

 position occurring, especially in drying. On this account, I have not 

 at present succeeded in isolating it in a sufficiently pure state for 

 analysis. 



