HYDRIODIC ACID AS A BLOWPIPE REAGENT. 67 
For the purpose of enabling me to point out presently certain relations which exist 
between the iodide coatings of the elements examined, I have arranged them on the 
accompanying chart, not in accordance with the colours, but in accordance with the position 
which the respective elements occupy in Mendelejeff’s periodic system. In describing these 
coatings, it will, however, be more convenient to group them according to the colours 
which characterize them. 
Description of Coatings. 
Arsenic—Reddish-orange coating. Plate I, fig. 1. 
Lead—Chrome yellow. Plate I, fig. 2. 
Tin—Brownish-orange. Plate IL, fig. 6. 
Silver—Faint greyish-yellow coating when cold, bright canary-yellow coating when hot. 
Coating just beyond the assay. Plate III, fig. 12. 
Antimony—Orange-red coating. Plate I, fig. 3. 
Mercury—Scarlet and yellow coating. Coating very volatile. Yellow coating evanescent, 
changing to scarlet after a time. The scarlet coating continuous near assay, distri- 
buted in spots through the yellow coating farther away from assay. These spots 
gradually increase in size and number until the yellow coating has entirely disap- 
peared. Plate I, fig. 4. | 
Selenium—Reddish-brown coating. Plate IE, fig. 7. 
Tellurium—Purplish-brown coating, limited near assay by deep brown border. Plate I, 
fig. 5. 
Bismuth—Chocolate-brown coating, sometimes fringed with red near assay. Plate IL, 
fig. 13. 
Gold—Faint brownish-yellow coating farther away from assay—pink to purple near assay. 
Coating near assay. 
Cobalt—Greenish-brown coating, edged with green. Brown coating evanescent, passing 
ultimately into faint green. Brown coating disappearing at once when breathed 
upon. 
 Thallium—Orange-yellow coating near assay—purplish-black over salmon farther away. 
The entire coating becomes ultimately yellow. Plate IT, fig. 8. 
Molybdenum.—Deep ultramarine coating. Coating permanent. The coating is an oxyd. Plate 
RUS fies 1. 
Tungsten. 

Faint greenish-blue coating near assay. The coating is an oxyd. (The coating 
comes out best by dropping an additional quantity of hydriodic acid upon the 
tablet near the assay after the operation.) Plate III, fig. 14. 
Copper....... 
Cadmium... \ Give white coatings. 
These three white coatings are best produced upon tablets which have been smoked 
over a gas flame. A fine surface of lampblack is thus obtained, which serves much better 
than charcoal. This method is illustrated in the case of copper by fig. 10. Plate IT. 
(The choice of adjectives descriptive of the colours of these coatings is based upon a 
spectroscopic examination of them conducted, at my request, by Dr. Coleman. The paper 
containing the details and results of the examination, I beg herewith to present to the 
Society.) 
