OF METALS OF THE PLATINUM GROUP. 
04 1 . 
flame in lime crucibles, and allowed them to cool in the crucibles. I employed about 
65 grms. for each of these experiments. 
Upon examination I found both of these alloys to be malleable, so that the difference 
between these results, as regards brittleness, is probably to be accounted for by the 
fact that the slow cooling enables a fine network of ci’ystals to form with resulting 
toughness. 
The process adopted for the determinations in the platinum-palladium series of 
alloys was the following :— 
Of each portion of the alloy to be analysed fifty grain determinations were taken 
and dissolved in nitrohydrochloric acid and evaporated nearly to dryness, these 
resulting chlorides re-acidified with hydrochloric acid and again evaporated nearly to 
dryness. 
The re-evaporated chlorides then dissolved up in water and the respective solutions 
of each determination diluted to about 150 c.c. liquid capacity; when cold the palla¬ 
dium was precipitated by mercury cyanide. The precipitate thus obtained was 
allowed to stand for twenty-four hours in a slightly warmed atmosphere, as I have 
found by experience that the precipitate of palladium cyanide comes down better 
under these circumstances. 
This precipitate, collected on filters, washed, dried, and ignited, gives the whole 
quantity of pure metallic palladium in the alloy. 
To obtain the platinum from the mother liquors, from which the palladium cyanide 
had been precipitated, these solutions were in each determiatnion evaporated to about 
30 c.c. capacity, and the platinum was then precipitated by ammonium chloride. 
The precipitate of the double salt of platinum ammonium chloride was then 
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, washed and digested in 
weak 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 of pure platinum 
in the proportion of— 
Palladium . 
P latinum . 
and also of— 
Platinum . 
Palladium . 
in the case of the alloys marked H, 
85 1 
15 j 
in those marked 
I. 
the results of which confirmed the accuracy of the process employed. 
mdcccxcii.—A, 
