90 Capt. P. Yorke's Experiments and Observations 



pale brown tint. The quantity of oxide actually obtained 

 from the precipitate by igniting and weighing it, amounted to 

 •132 grain, but part was lost. 



30. Some pure protoxide of lead, obtained by heating the 

 subnitrate in a platina crucible, was put into a phial filled 

 with the solution of carbonic acid ; another portion of the 

 same oxide was put into a phial filled with distilled water : 

 both phials were closed by ground-glass stoppers and ce- 

 mented. In the distilled water a quantity of a white floccu- 

 lent substance formed above the yellow oxide ; in the carbonic 

 acid no change could be observed for some time. At the 

 end of a month a small quantity of a white substance could 

 be perceived among the oxide. When the liquids from these 

 arrangements were tested after the lapse of that time, the addi- 

 tion of sulphuretted hydrogen produced no effect in the car- 

 bonic acid solution ; but it immediately struck a deep brown 

 with the distilled water, which also reddened turmeric, and 

 gave a precipitate with bisulphate of potash and solution of 

 carbonic acid as in prior experiments with metallic lead. 



31. Bright slips of lead were put into the solution of car- 

 bonic acid (a), and to guard against the possibility of the dif- 

 ference of action being owing to any other substance than the 

 carbonic acid, a part of the same solution was boiled for some 

 time to expel the acid, and similar slips of lead introduced into 

 it (b). The next day the liquid in (b) was milky, in (a) the 

 lead continued bright for more than a week ; while white cry- 

 stalline flakes had formed in the other, in which, in fact, the 

 effects were altogether similar to those obtained in previous 

 experiments with distilled water. The liquid from (a) gave a 

 barely perceptible tint on the addition of a solution of sulphu- 

 retted hydrogen. 



On the Carbonate of Lead, 



32. Carbonate of lead was prepared by precipitating a so- 

 lution of the subacetate by a current of carbonic acid gas. 

 The carbonate thus obtained was well washed with distilled 

 water; but when a large quantity had been used, the washings, 

 when tested by sulphuretted hydrogen, still indicated a minute 

 portion of lead to be present : further washing did not diminish 

 the effect. When this had arrived at the minimum, sulphuretted 

 hydrogen gave a pale brown tint ; and solution of bicarbonate 

 of potash produced a very faint milkiness after standing some 

 time. When the solution of carbonic acid was passed through 

 carbonate placed on a filter, the filtered liquid gave an im- 

 mediate milkiness on the addition of bicarbonate of potash, 



