94 



Mr. E. Scliuuck on the CGlouring and 



[Recess_, 



The simplest formula with which the composition of the substance, com- 

 bined with the oxide and chloride of lead, agrees is H^g NO^-, which re- 

 quires 





Calculation. 



A 



Experiment. 





. . . 372 



46-03 



45-80 



H« ... 



46 



5-69 



5-87 



N 



14 



i-73 



1-71 



o„ ... 



376 



46-55 



46-62 





808 



100-00 



100-00 



This analysis, though, like the first, of little value in itself, seems to 

 point to the conclusion that the extractive matter has a tendency to undergo 

 a change, which consists in the absorption of water, and which is probably 

 promoted by the action of strong acids. There is, however, another way 

 of explaining its results, which will be given when I come to review the 

 whole of the analytical data. 



A portion of the alcoholic solution from which this lead compound was 

 precipitated was evaporated, when it left a brown syrup, some of the pro- 

 perties of which are not without interest. When heated in a crucible it 

 began to boil, evolved acid fames, consisting partly of hydrochloric acid, 

 and left after combustion much charcoal, which burnt away, leaving a little 

 white ash. The watery solution was strongly acid. After being mixed 

 with a solution of oxide of copper and an excess of caustic alkali it became 

 green, and, on being boiled, the liquid deposited suboxide of copper ; but 

 this reaction was probably due to an admixture of some impurity or of some 

 product of decomposition. On adding to the alcoholic solution an alcoholic 

 solution of acetate of lead, a cream-coloured precipitate fell, which, after 

 being filtered off and washed with alcohol, was treated with dilute sulphuric 

 acid. The filtered liquid, after being made alkaline, did not reduce oxide 

 of copper ; but, on the other hand, the liquid filtered from the cream- 

 coloured precipitate gave with amm^onia a white precipitate, which, on being 

 treated in the same way as the other, was found to contain, in combination 

 with oxide of lead, a substance which, in conjunction with caustic alkali, 

 readily reduced the oxide. The lead compound, the analysis of which has 

 'ust been given, may indeed, as I shall show further on, have consisted of 

 a mixture of equal parts of two lead compounds, viz. of the compound of 

 an extractive matter and of that of another body having the composition 

 of glucose. The watery solution of the syrup, on being mixed with hydro- 

 chloric acid and boiled, becam.e brown, and deposited dark brown flocks. 

 The filtered liquid left on evaporation a residue, which, on being treated 

 with water, dissolved only in part, an additional quantity of brov/n flocks 

 being left undissolved. These flocks were very little soluble in boiling al- 

 cohol, but they dissolved readily in a mixture of alcohol and ammonia. 

 The liquid filtered from the flocks left on evaporation a yeliov/ syrup mixed 

 with a quantity of needle-shaped crystals arranged in star-shaped masses. 



