104 



Mr. E. Scliimck on the Colouring and 



[Eecess^ 



The composition of the substance, combined in this case with oxide and 

 chloride of lead, corresponds, if the great excess of hydrogen be disregarded, 

 v/ith the formula C^^ H.^^ NO3-, which requires 





Calculation. 



Experiment. 



c.. ... 









372 



51-81 



51-66 



H„ 



36 



5-01 



5-79 



N 



14 



1-95 



2-17 



O3, ... 



296 



41-23 



40-38 





7l8 



100-00 



100-00 



This formula differs, as will be seen, only by three atoms of water from 

 that to which the first analysis of the preceding series led, though, like the 

 latter, it does not represent a pure unmixed substance. It may therefore 

 be inferred that the precipitate produced in urine by neutral acetate of lead 

 contains the same extractive matters as the precipitate which basic acetate 

 of lead gives in the filtrate. This conclusion was confirmed in a very satis- 

 factory manner by subsequent experiments. 



C (1857). 



The facility with which the hydrochloric acid derived from the chloride 

 of sodium of the urine is removed from solutions of urinary extractive 

 matters containing the acid, by means of oxide of mercury and metallic 

 mercury, led me to try this method of purification on a somewhat larger 

 scale than before. For this purpose a quantity of urine was mixed with 

 acetate of lead, and to the liquid filtered from the precipitate basic acetate 

 of lead was added, which produced, as usual, a second precipitate. This 

 precipitate was filtered off, washed, and treated with dilute sulphuric acid. 

 The excess of acid having been removed by means of carbonate of lead, the 

 filtered liquid was evaporated in the air-current. The residue left on eva- 

 poration was treated with cold water, which left undissolved a mixture or 

 compound of chloride of lead and extractive matter. This was filtered off, 

 and the lead still contained in solution was precipitated by a current of 

 sulphuretted hydrogen. The filtered liquid containing hydrochloric acid 

 was now agitated with freshly precipitated oxide of mercury, to which some 

 metallic mercury was added. As soon as it had become free from chlorine, 

 it was again filtered and evaporated in the air-current. The glutinous 

 residue left on evaporation was treated with cold alcohol, in which only a 

 trace dissolved. That which was left undissolved by the alcohol was now 

 dissolved in water, and through the solution, which contained an abundance 

 of mercury, a current of sulphuretted hydrogen was passed, and the filtered 

 liquid was evaporated. The residue was treated with cold alcohol. A pale 

 yellow glutinous substance was left undissolved, which was dissolved in 

 water. The watery solution was mixed with ammonia, with which it gave 

 a flocculent precipitate. To the filtered liquid there was added acetate of 

 lead, and the precipitate thereby produced was filtered off, washed, and 



