Rinmann's Green Pigment

Dissolve together in sufficient water 1 part of sulphate of cobalt and 3 of sulphate of zinc; precipitate with carbonate of soda, wash the precipitate, and calcine it.

Pink Saucers

See Red Dyes, further back.

Plates, Daguerreotype, are prepared by cleaning and polishing the silver surface, exposing it to the vapour of dry iodine, or tincture of iodine, or iodide of bromine, or bromide of calcium. After having the image thrown on them, they are exposed to the vapour of mercury. But the manipulations and precautions necessary to the success of the operation, are too numerous to detail here.

Plate-Boiling Powder

Equal parts of cream of tartar, alum, and common salt. A small quantity added to the water in which plate is boiled gives it a silvery whiteness.

Black (Oxiphorous) Platina

Dissolve protochloride of platinum in a boiling solution of potash, add alcohol in small portions till effervescence ceases. Boil the black precipitate successively with alcohol, hydrochloric acid, and potash, and finally 4 or 5 times with water.

Platinated Asbestos

Dip asbestos in a solution of chloride of platinum, and heat it to redness. It causes the inflammation of hydrogen in the same manner as sponge platina. - Dr. Hare.

Platinized Silver

Silver plates for Smee's voltaic battery are covered with pulverulent platinum by adding a little bichloride of platinum to acid water, and decomposing the solution by the use of a platinum terminal in connexion with the copper of a battery, the silver plate to be platinized being in connexion with the zinc. Platinum itself is sometimes platinized in the same way. Sometimes the plates are "platinized without the battery. The following solution is used by Dr. Wright for the plates of his battery: - Saturated solution of chloride of platinum 1/2 drachm, sulphuric acid 1 1/2 drachm, water 2 drachms. Dip the plates in it for a few seconds, and wash them quickly.

Chlorides of Platinum

Dissolve platinum in nitro-hy-drochloric acid, and evaporate with a gentle heat to dryness. The red bichloride remains. Heated to 450°, the protochloride remains.

Platinum Sponge

Dissolve separately in rectified spirit, chloride of platinum and sal ammoniac. Mix the solutions, and heat the precipitate to redness. For balls for hydrogen lamps, form the precipitate into balls while moist, and afterwards burn them.

Poison

See Beetle Wafer, Bug Poisons, Rat Poison; Phosphorus Paste, Blights, Remedies for, etc.

Polish

See French Polish.

Polish for Boots, etc

See Blacking.

Polishing Powder for Specula

Lord Ross. Precipitate a dilute solution of sulphate of iron by ammonia in excess; wash the precipitate, press it in a screw press till nearly dry; then expose it to heat until it appears of a dull red colour in the dark.

Pot Pourri

See Perfumery.

Carbonate of Potash

Salt of Tartar. Subearbonate of potash. See PotassAe Carbonas, and PotassAe Carbonas purum, Pocket Formulary.

Potash Chlorate

See Chlorate of Potash.

Remedies for Potato Disease

The following are some of the more recent propositions for the prevention of this terrible and well-known plant epidemic:

1. Some direct that the haulms and leaves should be entirely removed as soon as the least symptom of disease shows itself in them. The roots may grow on to full size without becoming affected.

2. The Chevalier Claussen's Cure. The potatoes, before planting, are wet with water acidulated with sulphuric acid (1 part to 500), and, before they are dry, powdered sulphate of lime is thrown over them. This plan has been found a very efficient one.

3. Mr. T. Herapath's Plan. The roots, before planting, are allowed to become dry, and then dipped for a short time in a weak solution of sulphate of copper. The land is dressed with a mineral composition (2 parts of lime to 1 of salt) instead of farmyard manure. This process also has been attended with considerable success.