162 On tiro Metals, found in the Hack Poivder 



it has not only been little noticed, but absolutely seems to 

 have been rejected from general practice. 



By sundry experiments I have ascertained, that, on an 

 average, from 300 to 500 grains of phosphate of lead may be 

 daily obtained from tlie urine generated by one healthy 

 individual; by employing, for that purpose, a solution of 

 nitrate of lead. 



Very pure phosphoric acid may likewise be connnodiouslV 

 manufactured by means of nitrate of barytes. The phos- 

 phate thus formed is to be, in its turn, decomposed by sul- 

 phuric acid. 



This process applies equally to separate the phosphoric 

 acid from urine, or from the impure acid obtained from 

 calcined bones. 



After bones have been calcined and powdered, they should 

 invariably be washed before the affusion of sulphuric acid, 

 that no neutral soluble salt remain : this operation may be 

 readily performed by suspending the pulverised ashes in a 

 large quantity of water ; and this method deserves to be 

 followed on many other occasions. I remain, sir. 



Your obedient servant, 

 Long Acre, Jos. HUME. 



Nov. 19, l!-.04. 



XXIX. On tno Metals, fuuJid in the Hack Ponder remaining 

 after the Solution of Plaiina. By Smithson Tennant, 

 Esq. F.R.S* 



v-* PON making some experiments, last summer, on the 

 black powder which remains after the solution of platina, I 

 observed that it did not, as was generally believed, consist 

 chiefly of plumbago, but contained some unknown metallic 

 ingredients. Intending to repeat my experiments with 

 more attention during the winter, I mentioned the result of 

 them to Sir Joseph Banks, together with my intention of 

 communicating to the Royal Society my examination of 

 this substance, as soon as it should appear in any degree 

 satisfactory. Two memoirs were afterwards published in 

 France, on the same subject; one of them by M. Descotils, 

 and the other by Messrs. Vauquelin and Fourcroy.. M. 

 Descotils chiefly directs his attention to theeff'ects produced 

 by this substance oh the solutions of platina. He remarks, 

 that a small portion of it is always taken up by nitro-muria- 



• From the Tramactioniof the Royal Society of London for 1804. 



tic 



