92 



Mr. E. Sclmnck on the Colouring and [Recess^ 



coloured precipitate. Having, as I supposed, added sufficient acetate of 

 lead to precipitate about one half of the matter in solution, I filtered the 

 liquid from the precipitate (6), and then added more of the lead solution, 

 which produced a precipitate of a pure cream-colour (c) . This was filtered 

 off, washed with alcohol, dried i?i vacuo, and submitted to analysis. It 

 contained, like many of the lead compounds subsequently analyzed, chloride 

 of lead, which had to be estimated. By attempting to remove all the 

 hydrochloric acid from the solution of extractive matter before precipitation, 

 I ran the risk of producing decom.position in the organic substance. 



I. r0895 grm. of this compound, burnt with oxide of copper and oxygen, 

 gave 0*7765 grm, carbonic acid and 0*2175 grm.. water. 



ri580 grm., burntwith soda-lime, gaveO-1355 grm. chlorideof platinum 

 and ammonium. 



0*7780 grm. gave 0°6240 grm. sulphate of lead. 



0*9190 grm. dissolved in nitric acid gave with nitrate of silver 0*0795 grm. 

 chloride of silver, equivalent to 0*0772 grm. chloride of lead. 

 These numbers lead to the following composition : — 



C... 19*43 



H 2*21 



N 0*73 



16-97 



PbO 52*26 



PbCl 8-40 



100*00 



After deducting the oxide and chloride of lead, and calculating the 

 composition in 100 parts of the organic substance combined with them, 

 this composition will be found to correspond with the formula Cq^ H39 NO^q, 

 which requires 



Calculation. Experimeut. 

 j\ 



372 49*93 49*39 



Hg'g 39 5-23 5*61 



N 14 1*87 1-85 



O,, 320 42-97 43*15 



745 100-00 100*00 

 No importance is to be attached to this formula, which is merely an em» 

 pirical expression for the composition of the substance, or mixture of sub- 

 stances, prepared in the manner described. As a guide to further experi- 

 ments, the analysis was, however, not without use. The very small 

 proportion of nitrogen obtained showed that the substance was probably 

 free from the urinary constituents containing much of that element, and 

 that the lead compound contained extractive matter only ; but v/hether the 

 latter consisted of only one substance or of several was doubtful, as the 

 method of preparation afforded no guarantee for its purity. 



The lead precipitate (5), which, it was to be presumed, had the same 

 composition as the one analyzed, was now examined. It was suspended in 



