A BLOWPIPE REAGENT—BOWMAN. 363 
ArT. IV.—Porassic JopIDE aS A BLowripE REAGENT.—By 
FrReD A. Bowmay, M. A., B. E. 
(Read 10th February, 1890.) 
In the Transactions of the Royal Society of Canada for 1883 
there is a paper by Prof. E. Haanel, Ph. D., “ On the Applications 
of Hydriodic Acid as a Blowpipe Reagent.” In this paper the 
author states how he was led to the use of iodide coatings in 
place of the ordinary characteristic oxides deposited on the char- 
coal, and his method of making and using the hydriodie acid, and 
also the little Plaster of Paris tablets. Many of the metals yield 
very characteristic coatings by this method, and the paper is illus- 
trated by beautifully coloured diagrams of some of them. 
While doing advanced blowpipe work under Prof. Kennedy at 
King’s College, Windsor, he advised my following out Dr. Haanel’s 
experiments. This I did, and easily got all his results. Wefound 
however one serious difficulty in the practical application of the 
method. Uydriodic acid is an unstable compound, the iodine 
tending to separate and come down as iodine crystals. These can, 
it is true, be re-dissolved by passing a stream of hydric sulphide 
through the acid for a little while, but this requires a laboratory 
and removes the reagent from a portable blowpipe outfit. Then 
again the acid must be prepared by the user. 
These objections led Prof. Kennedy to suggest the use of a 
solution of potassic iodide and an acid. This I tried with most 
satisfactory results. The method of using the reagent is as fol- 
lows: The assay being placed in a little hollow near one end of 
one of the plaster tablets, one or two drops of the solution of 
potassic iodide are deposited on and around it, and are absorbed 
by the tablet, then a drop or two of acid, preferably sulphuric, 
is added and the assay heated before the blowpipe. The potassic 
iodide is decomposed and vapours of iodine are given off. Some 
of the iodine unites with the assay to form an iodide of the metal 
init. These iodides, many of them of brilliant hues, are deposited 
