310 Chemical Composition of the Brown Lead Ore. 
acid was thus proved to a certainty. The following, therefore, are 
the constituents of this mineral; viz. lead, lime, phosphoric acid, 
chlorine and fluorine. 
Analysis. . 
The determination of the quantitive composition of the Polyspha- 
rite was effected by means of three analyses, made with the utmost 
possible care, in which the method of proceeding was as follows? 
(a.) One gramme of the finely powdered mineral was dissolved 
in the cold, in order to prevent the escape of any muriatic acid ; 
and the solution, diluted with water, was precipitated by nitrate of 
silver. According to the mean of three trials, the quantity of chlo- 
ride of silver obtained was 0.106, which corresponds to 0,0200 of 
muriatic acid,* or to 0.01765 of chlorine. 
(b.) After the precipitation of the chloride, and the removal of the 
excess of nitrate of silver from the liquid by means of muriatic acid— 
the precipitate thus obtained being carefully washed with distilled wa- 
ter—a stream of sulphuretted hydrogen was passed through the fluid, 
and the sulphuret of lead obtained was estimated. In two experi- 
ments the sulphuret of lead was converted into sulphate of lead, by 
means of concentrated nitric acid. These precipitates corresponded 
to 0.7217 of oxide of lead, or to 0.670 of metallic lead. 
(c.) The lime was thrown down, by means of sulphuric acid, from 
the liquid remaining after the precipitation of the lead, after that I 
had warmed, filtered and mingled it with alcohol. The voluminous 
precipitate obtained was separated by the filter: the liquid was some~- 
what concentrated, and the sulphate of lime thus obtained added to 
the first precipitate; and the whole dried and ignited. Its weight 
amounted to 0.1558, which corresponds to 0.0697 of lime. As the 
proportions of chlorine, lead and lime in this mineral were ascertain- 
ed by three analyses, so also, the proportions of phosphoric and flu- 
oric acids were found, through the loss of weight in these processes. 
* As these researches sustain a peculiar relation to those of Mr. Wéhler upon the 
composition of the Green Lead Ore, and to those of Mr. G. Rose upon the chemical 
constitution of the Apatite, I have, for the sake of favoring a comparison, employed 
in this memoir the same determinations, for the most part, as were made use of by 
those chemists. 
