HYDRIODIC ACID AS A BLOWPIPE REAGENT. WA 
driodic acid may be allowed to fall upon the coating, and the moistened spot be touched with 
the oxidizing flame. By this process the arsenic and tellurium are converted into iodides. 
The residue of the assay may then be further examined in the usual manner by moistening 
with hydriodic acid upon a new tablet, or the old one after it has been cleansed from the 
volatile iodides by the heat of the blowpipe flame. 
1X.—BunsEn’s METHOD oF FLAME REACTIONS. 
I think it is proper here to mention that Bunsen has employed hydriodic acid as a 
test for the recognition of substances in his method of flame reactions. His method is as 
follows : 
The substance under examination is suspended by means of a fibre of asbestos in 
the hottest part of the Bunsen flame. Any volatile products are deposited upon a glazed 
porcelain dish filled with water, and held just over the assay in the flame. These deposits, 
termed element films, are then examined for purposes of identification with various 
reagents, among these fuming hydriodic acid, emitted from decomposing phosphorus 
iodide. By the vapours of this reagent the films are converted into iodides of character- 
istic colours. 
By this method eleven substances can be recognized. The method described in this 
paper does not alone include these eleven elements, but serves for the detection of seven 
others, i. e., copper, tin, silver, gold, cobalt, molybdenum and tungsten. If sulphur, 
which in the case of sulphides is recognized by the hydrogen sulphide emitted, and 
gallium, which probably gives a coating, be added, the method here presented covers a 
range of twenty substances. However admirable the method of Bunsen, it will at once 
be seen that for field work it is wholly impracticable, nor does it permit the recognition of 
one or more substances in presence of each other. 
X.—SUMMARY OF THE ADVANTAGES OF THE METHOD PRESENTED IN THIS PAPER. 
1. One single operation may be sufficient for the satisfactory identification of two or 
more substances in presence of each other. This was shown especially in the case of 
Lehrbachite and Kobellite. 
2. Hydriodic acid as a reagent covers a wider range of substances than any other 
reagent which has yet been applied in blowpipe analysis. 
3. Most minerals may be subjected to examination at once upon the tablet without 
previous roasting or other secondary operations. 
4. The operation is rapid, requires little exertion, and is more easily conducted than 
many other operations now in practice among mineralogists for the determination of the 
elements in question. 
5. The tablets are cheap, easily made, cleanly, and occupy little space for storage. 
They are much to be preferred on these grounds to charcoal, even for examinations of oxyd 
coatings, which in some cases come out much more finely and distinctly upon thé tablets 
than upon charcoal. Some of the coatings on the tablet per se have been sketched and are 
presented with this paper. An example of this is given in Plate IL, fig. 9. 
