66 E. HAANEL ON THE APPLICATION OF 
ruler, into strips of the size required for the tablets, most conveniently 4 x 15 inches. When 
dry, the cast is removed from the glass and broken along the grooves, made as indicated, into 
tablets. The surface next to the glass, which is smooth and level, is used for the deposi- 
tion of the iodides. A small cavity at one end, made with a charcoal borer, serves to fix 
the position of the assay. 
JIT.—PREPARATION OF Hypriopic ACID. 
The hydriodic acid used in the investigation was made by suspending a quantity of 
iodine in 7 oz. of water, and allowing hydrogen sulphide to bubble through it until the 
liquid became clear. More iodine was then added. Hydrogen sulphide was again passed 
through the liquid, and this process repeated until 5 oz. of iodine had been converted into 
hydriodic acid. The acid retains for a time a surplus of hydrogen sulphide, which is rather 
an advantage than otherwise, since it prevents the decomposition of the acid, and in no 
wise interferes with the reactions. The instability of the acid is practically of little impor- 
tance. Any dissolved or precipitated iodine, which may occur after some weeks exposure 
to light and atmosphere, unavoidable during its use, is readily reconverted by hydrogen 
sulphide into hydriodic acid. 
IV.—MANIPULATION. 
The assay is placed on the tablet in the cavity provided for its reception. One or two 
drops of hydriodic acid are now allowed to fall upon it, which are at once absorbed by the 
tablet immediately around the assay. The tablet is now held in an inclined position in 
exactly the same manner as charcoal when used for the production of coatings, and the 
point of the oxydizing flame directed upon the assay. Certain oxyds, chlorides, bromides, 
sulphides, etc., are thus decomposed by the hot vapour of hydriodic acid rising from the 
tablet around the assay, and any volatile iodides formed are deposited upon the tablet around 
and beyond the assay as coatings. 
V.—RESULTS. 
It is proper here to state that the investigation of the different elements in accordance 
with the method just sketched is not yet completed. As far as it has been carried and 
is described in this paper, it has proven beyond expectation fruitful. Seventeen ele- 
ments have furnished more or less brilliant coatings, readily distinguished from each 
other by tint, difference in degree of volatility and certain typical characteristics, not easily 
described, depending on the mode of their deposition. Since no one can be expected from a 
mere verbal description to form an idea of the decisiveness and sharpness of the distinction 
of the different coatings, and the superiority of this method over others employed in blow- 
pipe analysis to determine the elements in question, and since it is important to the analyst 
to haye the different typical coatings for comparison, my friend, Dr. Coleman, has been kind 
enough, at my request, to reproduce these coatings by water-colour sketches, which are 
appended to this paper.* It is only by comparing the actual coatings with these represen- 
taverns, | that the skill exhibited in thus accur a copying them can be br 

* The paper “ On the wets ation of Hydriodic Acid as a Blowpipe-reagent” was ares ane bya chart on which 
the coatings obtained were represented by water-colour sketches. On account of the cost of reproducing them by 
chromo-lithography it became necessary to select from the number presented those which were most characteristic 
and served best to illustrate the value and advantages of the method described in the paper. 
