244 MR. E. SCHUNCK ON THE 



to some of these lead compounds, since it is not precipitated 

 from its watery solution by acetate of lead, when in a state of 

 purity. The filtered liquid which is much paler in colour than 

 it was before the addition of acetate of lead, gives with basic 

 acetate of lead a second precipitate of a pale cream-colour, 

 which consists of the lead compound of the extractive matter 

 mixed with some basic chloride of lead. Both this and the first 

 precipitate give when treated with sulphuric or muriatic acid 

 yellow liquids, which after being filtered from the sulphate or 

 chloride of lead and boiled, yield brown flocks exactly like 

 those obtained from urine itself. The liquid filtered from the 

 precipitate with basic acetate of lead is almost colourless. It 

 gives, however, on the addition of ammonia an almost white 

 precipitate, the quantity of which is much less than that of 

 either of the two other precipitates. Now this precipitate 

 exhibits a very remarkable peculiarity. It contains in most 

 instances in combination with oxide of lead, a small quantity 

 of a substance which by decomposition with acids yields 

 indigo-blue. The first time that I treated this precipitate 

 with acid I was surprised to observe that the liquid became 

 immediately of a purplish-blue colour, and deposited after 

 filtering and standing a small quantity of a substance, which 

 on examination was found to consist chiefly of indigo-blue. 

 This phenomenon was observed on so many occasions that I 

 came to the conclusion that the occurrence in urine of an 

 indigo-producing body similar to indican, was by no means an 

 unusual circumstance. 



In order to ascertain whether this body is present, I adopt 

 the following method. The urine having been mixed with 

 basic acetate of lead until no more precipitate is produced is 

 filtered, and after the precipitate has been washed with water 

 the liquid is mixed with an excess of ammonia, which always 

 produces more or less of a white or yellowish-white precipitate. 

 This precipitate is collected on a filter, slightly washed with 

 water and then treated with dilute sulphuric or muriatic acid 



