10 E. HAANEL ON THE APPLICATION OF 
Boulangerite—The sulphur contained by this mineral is recognized by the odour of hy- 
drogen sulphide emitted by the assay when moistened with hydriodic acid. The 
yellow of the lead coating is seen near the assay, that of antimony, rendered more 
yellowish by admixture of lead coating, farther away from assay. 
Amalgam.—Silver near assay surrounded by yellow and red iodides of mercury. The 
yellow iodide of mercury gradually changes to red, which distinguishes the mer- 
cury from tin, lead, arsenic and antimony. Plate IV, fig. 16. 
The mercury is eliminated and deposited first ; the silver toward the close of 
the operation. 
Tin amalgam—An amalgam of tin was made and a coating obtained from it for comparison 
with that just described. 
The yellow of the tin is seen side by side with the red of the mercury. 
This coating was sketched when it had become permanent i., e., when all the 
yellow mercury iodide had changed to the red iodide. 
Lehrbachite.—The coating shows the lead close to the assay, surrounded by the red iodide 
of mercury, and the whole surrounded by the reddish-brown coating characteristic 
of selenium. Plate IV., fig. 17. 
Chilenite—Silver close to the assay, surrounded by the more volatile coating of bismuth. 
The coating must be examined when hot, since the brownish coating of bis- 
muth obscures the silver coating by gradually creeping over it on cooling. 
(The coating was sketched when hot). Plate IV., fig. 19. 
Nagyagite—Two sketches of coatings are given. The first is of aspecimen containing a 
less percentage of tellurium than the second of an other specimen. In the former 
we have the combination colour of the mixed coatings of lead and tellurium ; in the 
latter the complete separation. In this the lead is shown close to the assay sur- 
rounded by the more volatile tellurium ; this is shown on Plate IV, fig. 20. 
Kobellite—Lead near assay. Bismuth and antimony overlapping, as brownish-red coating 
farther away from assay. Plate IV., fig. 18 
VIII.—SprctaL METHODS OF SEPARATION. 
Tin and lead, when occurring together in an assay, give a compound coating of a 
brownish-yellow colour not easily differentiated from other similar coatings. To effect, 
however, a satisfactory separation of these two elements, advantage may be taken of the 
fact that the iodide of tin does not so readily deposit as lead upon a surface of lampblack. 
By carrying out the operation upon a smoked tablet with an alloy of lead and tin, the 
iodide of lead will be deposited near the assay, the iodide of tin, on the other hand, will 
be deposited at a much greater distance from the assay, as a thin pale yellowish and very 
characteristic coating. This is shown by the sketch of the coating obtained. 
In the case of minerals containing arsenic and Jead or bismuth and tellurium, which 
would give compound coatings with colours not easily identified on account of the simi- 
larity of the colours of the individual coatings of the components, advantage may be taken 
of the fact that arsenic and tellurium are per se more volatile than lead and bismuth. 
The separations are here best effected by the process of roasting upon a dry tablet. To 
identify the arsenic or tellurium, which will have deposited as coatings, a drop of hy- 
