Prop., &c. As the hydrate (Pt(HO)4), it is a bulky brownish powder; this, when gently heated, becomes black and anhydrous. It forms salts with the acids, and combines with some of the bases. The salts have a red or yellow colour, and a remarkable tendency to form double salts with the alkaline salts.
Obs. Both the oxides of platinum are reduced to the metallic state on ignition.
Platinous Oxide. PtO. Syn. Oxide of platinum. Prep. By heating to below redness the platinic chloride and digesting with hydrate of potassium the residue.
Prop., &c. A black powder, soluble in excess of alkali, and freely so in the acids, forming brown solutions of the platinous salts. These are distinguished from solutions of the platinic salts by not being precipitated by chloride of ammonium. Platinous oxalate, in fine copper-coloured needles, may be obtained by heating platinic oxide in a solution of oxalic acid.
Platinum Gas. Syn. Gaz-platine; Gillard’s gas. In Paris this gas is employed by gold- and silversmiths and electro-platers because it gives rise to no sulphur product and burns without giving off soot or smoke. It is free from smell. Steam is decomposed by being made to pass through a retort filled with red-hot charcoal. The hydrogen being freed from the carbonic acid which is associated with it, by means of crystallised carbonate of soda, is burnt from an Argand burner provided with numerous small holes. The flame, which
is not luminous in itself, is surrounded by a network of moderately fine platinum wire, which on becoming white-hot becomes luminous. It burns quite steadily, and its illuminating power is said to exceed slightly that of coal gas.
Platinum, Spongy. Prep. 1. By heating ammonio-chloride of platinum to redness.
2. Crude bichloride of platinum and chloride of ammonium are separately dissolved in proof spirit, and the one solution added to the other as long as a precipitate forms; this is collected, and, whilst still moist, formed into little balls or pieces, which are then dried, and gradually heated to redness.
Prop., &c. These have been noticed above. Small balls of spongy platinum are used for the hydrogen instantaneous-light lamp (Döbereiner’s lamp); but they are apt to absorb moisture from the atmosphere, and then lose their power of inflaming hydrogen, until they are re-dried and heated.
PLEURISY. Inflammation of the pleura, or membrane covering the lungs. The symptoms of pleurisy are a sharp pain in the side, which is rendered more acute when a deep breath is taken; quick, short, difficult inspiration; a quick pulse; and fever. Much pain is also experienced if the attempt be made to lie on the affected side.