Platinum sponge

Near-stoicheiometric mixtures detonate on sparking, or on contact with platinum sponge. 

Nickel and selenium interact with incandescence on gentle heating [1], as do also sodium and potassium, the latter mildly explosively [2], Uranium [3] and zinc [4] also incandesce when their mixtures with selenium are heated, and platinum sponge incandesces vividly [5], The particle size of cadmium and selenium must be below a critical size to prevent explosions during synthesis of cadmium selenide by heating the elements together. Similar considerations also apply to interaction of cadmium or zinc with sulfur, selenium or tellurium [6], Interaction of powdered tin and selenium at 350° C is extremely exothermic [7],... 

Pure hexachloroplatinic acid may be prepared by dissolving platinum sponge in hydrochloric acid under chlorine. 

Na2PtCl6 to ammonium platinum chloride (NH4)2PtCl6. The purified ammonium complex is then ignited to form platinum sponge. 

Platinum dichloride is prepared by heating platinum sponge in chlorine at about 500° C ... 

The platinum sponge used in this preparation should be either 99.99 or 99.999% pure. All other chemicals should be reagent grade. Only KCN, which generally assays 97-98% pure, is recrystallized from absolute methanol.5 It is dried at 50° for 2 hours before it is weighed, as are the KBr and [N2H6]S04. Distilled water is used throughout the entire preparation. 

This is usually accompanied by considerable evolution of heat and the reaction is very difficult to reverse. For instance, when cold platinum sponge is held in the vapors of alcohol absorption proceeds with enormous evolution of heat — the sponge becomes red hot and ignites the alcohol. This propetty has been used in some lighters 1... 

Platinum occurs in compact form as foil or wire, and in a state of very fine subdivision as platinum sponge and platinum black. Compact platinum has a silver-white color platinum sponge is a grayish, spongy mass, while platinum black is a black powder. 

Metals Soluble in Nitric Acid. — Strongly ignite 2 gm. of platinic chloride. A residue of platinum sponge weighing 0.752 gm. should be obtained. Digest this residue with dilute nitric acid (5 cc. of nitric acid and 20 cc. of water) on the water-bath for fifteen minutes, then filter, evaporate the filtrate on the water-bath, and ignite the residue so obtained. The weight of the latter should not exceed 0.005 gm. 

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