APPENDIX. 527 



3. 0-2716 grammes of urea yielded 2'0400 grammes of 

 ammonio-cliloride of platinum, corresponding to 0-2743 

 grammes of urea. 



To ascertain how far the presence of extraneous matters 

 might interfere with the accuracy of the results, sugar was 

 mixed with the urea, but the results were unaffected. The 

 next point was to ascertain whether the extractive matter 

 would yield ammonia under these conditions. For this pur- 

 pose Ragsky precipitated 120 grammes (nearly 4 ounces) of 

 fresh and healthy urina sanguinis, with acetate of lead, after 

 having previously separated the uric acid by means of some 

 hydrochloric acid. The precipitate was mixed with water, 

 decomposed by sulphuretted hydrogen, and the yellow fluid 

 thus produced evaporated to a syrup, and charred with sul- 

 phuric acid. The charred mass was subsequently extracted 

 with water, the solution evaporated, and finally treated with 

 alcohol and bichloride of platinum. This process gave no indi- 

 cation of the presence of ammonia. Having thus ascertained 

 that the extractive matters, which are normally present in 

 urine, exercise no adverse influence on the quantitative deter- 

 mination of urea by means of sulphuric acid and bichloride of 

 platinum, he next proceeded to determine by this method the 

 amount of urea present in divers samples of urine, in order to 

 compare the results with those obtained by the ordinary me- 

 thods. He found, after several experiments, that 7 grammes 

 (a little more than five drachms) of urine required about 3-5 

 grammes (or half the weight) of concentrated sulphuric acid. 

 If less of the acid be taken the charred mass will readily dry 

 up, and some loss of ammonia will be incurred in consequence. 

 The mixture of urine and sulphuric acid is kept in a moderate 

 state of ebullition, there is a great evaporation of water, and the 

 fluid turns black. The temperature rises higher and higher, 

 until at about 392 there ensues evolution of carbonic acid gas 

 in small bubbles. The cessation of the disengagement of gas 

 indicates that the urea present in the analysed urine is com- 

 pletely decomposed. The black residue is then thoroughly ex- 

 tracted with water and the solution filtered. The clear and 

 urine-yellow filtrate is finally evaporated in the water-bath, and 

 the sulphate of ammonia treated with alcohol and bichloride 

 of platinum. 



Since urine contains salts of potash and ammonia, which 



