(526 REPORT— 1897. 



tablets so fortifies them that they form a substitute, not only for charcoal, but also 

 for platinum wire and bone ash. They resist the action of the fluxes, borax and 

 metaphosphoric acid, and instead of beads in platinum loops we may with advan- 

 tage produce coloured glassy films on the surface of the white tablets. Oxidation 

 and reduction take place very readily in these films. All degrees of saturation 

 may be observed at once. The colour changes due to change of temperature may 

 be more accurately observed on account of the slower rate of cooling. 



In assay work, if a fragment of a tablet be heated to redness for a few seconds 

 and then pulverised, we have a material which may be moulded into a smooth cupel 

 which does not blister, and which very readily absorbs the lead oxide in cupellation. 



Potassium sulphocyanate, metallic iodine, potassium cyanide, potassium sul- 

 phide, and potassium cadmium cyanide are all easy to carry. With water they 

 easily dissolve, and therefore solutions may be prepared anywhere. In the labora- 

 tory more rapid and better work can be done with the solutions. Potassium sulpho- 

 cyanate is not always kept by the drugsrists, and its preparation by crystallisation 

 in the laboratory is tedious. The simplest way to prepare the iodine solution is to 

 mix fragments of potassium cyanide and sulphur, the latter a little in excess of 

 the molecular proportions, in a test tube and fuse together, adding water while yet 

 warm, and then adding metallic iodine to saturation. Dr Wirt Tassin, of Wash- 

 ington, uses a solid reagent made by fusing iodine and the sulphocyanate together 

 with a little sulphur, and then powdering. This, if stable, ought to prove very 

 satisfactory. 



Here is a very effective portable blowpipe lamp which costs less than two 

 cents. It consists of an ordinary druggist's tin salve box, with a piece of tin 

 bent to form a wick-holder. The cover is bulged so as to shut down over the 

 wick. The fuel is paraffin wax or stearin. The flame is smokeless, very hot, and 

 with great reducing power and free from sulphur. Once filled, it burns for more 

 than an hour. A test tube can be readily boiled over it. In private laboratories, 

 and in schools in towns, where the electric light has supplanted gas, and afield, 

 this httle piece of simple apparatus has proved itself very useful. 



Some reactions, not hitherto published, are those obtained by using the tablets 

 as infusible filters. Films are obtained, for which I propose the name ' solution 

 films,' to distinguish them from the sublimation films. 



If to a solution of a lead salt a little potassium sulphocyanate be added, a pre- 

 cipitate of lead sulphocyanate tends to form. When, however, no precipitate is 

 visible, if a drop be let fall on a tablet, instantly a bright-yellow spot is seen. The 

 delicacy of many tests may be greatly increased by making use of this property of 

 the tablets. It seems to be somewhat catalytic. Not only one, but as many ns 

 fifty or one hundred drops may fall upon the same spot, each drop deepening the 

 coloration. Various confirmatory tests by wet or dry methods may then be made. 



The iodine solution shows a remarkable power of dissolving gold. Gold leaf 

 dropped on its surface almost instantly dissolves. If the solution containing gold 

 be dropped on a tablet and the spot touched with the blowpipe flame, a fine pink 

 film appears. It is better to add ammonium hydrate to the solution till de- 

 colorised. One drop of solution containing one part gold, in thirty thousand 

 will show a fine pink. Fifty drops will show gold present in one part in six hun- 

 dred thousand and one hundred drops, one part in one million of solution. The 

 test, therefore, may be made quantitative. 



Platinum yields a slate-coloured film, chromium a film dark-green hot, and fine- 

 green cold Copper yields a purple film, which, treated with sulphuric acid, dis- 

 appears and darkens in oxidising flame. From some solutions the copper film is 

 black. If a copper solution be dropped on a tablet and heated vapours of hydro- 

 bromic acid be blown over it, the purplish-brown of cupric bromide will appear. 

 This will reveal copper, when present, one part in two million parts of solution. 



Iron gives a brownish film, which sulphuric acid turns to Venetian red, and 

 other acids remove. 4 little metaphosphoric acid added to the solution will pre- 

 vent the formation of the film. Cobalt yields a pink film, which becomes, on 

 hydration, a beautiful blue, and more strongly heated a black, which a dj-op of 

 strong acid potassium sulphate removes. 



