Section III., 1884. [ 77 ] Trans. Roy. Soc. Canada. 



III. — Blowpipe Reactions on Plaster of Paris Tablets. 



By E. Haanel, Ph.D., Victoria University, Cobourg. 

 (Read ]\Iay 22, 1884.) 



I. — Eeactions for Copper and Iron with Hydrobromig Acid. 



In a former paper entitled : " On the Application of Hydriodic Acid as a Blowpipe 

 Reagent," I described a method of rendering evident certain white iodide coatings, by pro- 

 ducing them upon blackened tablets. Since the publication of this paper I have sought 

 to do away with the necessity of using blackened tablets by searching for a reagent which 

 would, with the substances in question, give easily recognized coloured coatings. I have 

 succeeded in the case of copper, which gives with hydrobromic acid a dappled coating of 

 greyish-black OA^er purple. This same reagent also gives a very characteristic rust- 

 coloured coating with iron. These two coatings differ greatly in volatility ; that of copper 

 is very volatile, that of iron very much less so. This difference enables the analyst to 

 distinguish the copper and iron in presence of each other, since, if a mineral containing 

 copper and iron be treated on the tablet with hydrobromic acid and heated before the 

 blowpipe, the copper coating will be driven to a distance, while the iron coating will 

 appear immediately around the assay. The separation of the coatings is marked and 

 distinct. The reaction is eqixally sensitive for both. 



In many cases, a drop of hydrobromic acid allowed to fall upon the assay placed on 

 the tablet is quite suihcient, without subjecting the assay to heat, to produce around the 

 assay a characteristically coloured ring, declaring the presence of iron ; if the assay be now 

 subjected to the 0. F., the flame becomes coloured bluish-green, and the dappled coating 

 of copper makes its appearance. Fuming hydrobromic acid was used for these reactions. 



Blowpipe analysis is valuable, chiefly on account of its expeditiousness and the small 

 quantity of apparatus and reagents required for its operations. It is, therefore, in general, 

 not desirable to detract from its value by multiplying the ntimber of reagents or appliances 

 required, unless it can be shown that the detection of a substance or substances is rendered 

 thereby more certain and expeditious, and that an otherwise difficult sej^aration becomes, 

 by the use of the new reagent or appliance, not alone possible but sim^ile. These char- 

 acteristics are claimed for the new reagent, hydrobromic acid, since it not alone facilitates 

 greatly the detection of copper and iron in presence of each other, bu.t also in presence of 

 other lead-colourinsï substances such as cobalt and nickel. 



^a 



II. — Coating of Iron with Hydriodic Acid on Tablets. 



Iron giA'^es a very A^olatile feebly- violet coating Avith hydriodic acid on a tablet, but 

 its deposition on account of its A^olatility and its recognition on acount of its feebleness are 



