526 APPENDIX. 



on this subject have appeared almost simultaneously during the 

 last three months one by Ragsky, the other by Heintz. 



With regard to the quantitative determination of urea, 

 Ragsky 1 observes there is this great objection to its separation 

 either as a nitrate or oxalate, that both those salts are per- 

 ceptibly soluble, which prevents on the one hand their com- 

 plete precipitation, and on the other hand their perfect wash- 

 ing, on which latter account they retain a certain amount of 

 extractive matter. No other compound of urea being known, 

 adapted for its quantitative determination, Ragsky endeavoured 

 to apply the products of its decomposition to this purpose. 

 After several experiments made to this effect, with chlorine 

 and with nitrous acid, he found that concentrated sulphuric 

 acid answers the purpose best. For this purpose, a mixture 

 of one part of urea, with from three to four parts of concen- 

 trated sulphuric acid is introduced into a flask, and exposed to 

 the heat of a sand-bath, which must not exceed 572 to avoid 

 loss of ammonia. The decomposition of urea commences at 

 383 and the evolution of carbonic-acid gas is very lively at 

 392. In this process one equivalent of urea assumes the 

 elements of two equivalents of water, and transposing with the 

 latter is converted into two equivalents of carbonic acid which 

 escape as gas, and two equivalents of ammonia which remain 

 in combination with the sulphuric acid. 



C 2 N 3 H 4 2 + 2 HO + 2 (S0 3 , HO) = 2 (NH 4 0, S0 3 ) + 2 C0 2 . 



He determined, in this manner, accurately-weighed portions 

 of pure urea dried at 212 degrees, and determined the ammo- 

 nia subsequently in the form of ammonio-chloride of plati- 

 num. The following numbers will show how approximately 

 urea may be determined in this way. 



1. 0-2612 grammes of urea yielded 1-9323 grammes of 

 ammonio-chloride of platinum corresponding to 0-2598 

 grammes of urea. 2 



2. 0-3139 grammes of urea yielded 2-3175 grammes of 

 ammonio-chloride of platinum, corresponding to 0*3116 

 grammes of urea. 



1 Liebig and Wohler's Annalen, Oct. 1845. 



2 The English reader will see the accuracy of the result more clearly by reducing 

 the grammes to grains. From 4-022 grains used in the experiment, 4'001 were re- 

 covered. 



