90 M. C. Lea on the Platinum Metals. 
Where the solutions are so very dilute as these last, the boil- 
ing must be continued for some minutes.” 
Although the sulphocyanid test is very delicate, it is not equal 
to this, as was determined by a comparative trial. It is also lia- 
ble to the objection that when employed to examine mixtures, 
the presence of iron might be confusing. For although the re- 
action of ferric salts with sulphocyanid gives a different shade of 
red, yet it is to be observed that the two colors approach each 
other considerably when much diluted. Moreover, in using the 
sulphocyanid test, I find it best to acidulate the liquid strongly 
with chlorhydric acid, and to obtain chlorhydric acid absolutely 
ee from iron, so that it does not give the slightest coloration 
with the sulphocyanid ; it is generally necessary (in this country, 
f. 
to explain its cause. It is, however, unquestionably due to 4 — 
compound of ruthenium, and not to the production of any 
_ tion, is suspected, it is often advisable to boil the solution with a little chlorhydric — 
: previous e application cf the hyposulphite, sulphocyanid, or other test. 
| be given in the second part of this paper. Be the 
wi i : 
this ks Lage psc an examination of the reaction of 
