OF METALS OF THE PLATINUM GROUP. 
651 
ammonium chloride. This precipitate was then carefully collected on filters, dried, 
ignited, and weighed, the result being pure platinum. 
The small proportion of platinum remaining in the mother liquors was precipitated 
by means of pure metallic zinc as metallic platinum, which, when washed and digested 
in diluted hydrochloric acid, was collected, ignited, and weighed, the results being 
added to those obtained by the ammonium chloride precipitation. All these results 
were checked by standards of pure palladium and pure platinum in the propor¬ 
tions of— 
and of- 
Palladium . 
. . 85 
Platinum 
. . 15 
Platinum 
. . 85 
Palladium . 
. . 15 
j- in the case of the alloys marked H, 
5 
in those marked I, 
and the results obtained by analysing these standards confirmed my views as to the 
accuracy of the process employed. 
Alloy J. Platinum.90 parts. 
Phodium.10 ,, 
The process adopted for the separation and determination of the rhodium and 
platinum in this alloy is one that I have found by experience to be exceedingly 
accurate if conducted with care. (It is but little known, although it was described 
many years ago in Turner’s ‘ Elements of Chemistry, 5th edition, 1834, page 652.) 
Fifty grains of each of the alloys under examination were dissolved in nitro- 
hydrochloric acid, and evaporated to dryness. The dry chlorides were then dissolved 
in a warm solution of sodium chloride, and again evaporated to dryness. The resulting 
dry mass was then taken from the evaporating dishes and triturated in a porcelain 
mortar, from which the mass was then transferred to closed flasks and digested in 
absolute alcohol in a slightly warm atmosphere for 24 hours, the bottles being shaken 
from time to time. At the end of this period the whole of the platinum chloride is 
taken up in solution by the alcohol, and the rhodium chloride is left combined with 
the sodium chloride as a double chloride of rhodium and sodium insoluble in alcohol. 
This latter salt was washed with alcohol to remove any platinum chloride, and then 
dissolved in water. From this solution the metallic rhodium was obtained by direct 
precipitation with pure zinc ; it was washed, digested in w 7 eak hydrochloric acid, 
collected, dried, ignited, and weighed. 
The alcoholic chlorides containing the platinum chloride were evaporated and 
re-dissolved in distilled water. The platinum was then thrown down by means of 
4 O 2 
