The Meta-Encyclopedia

Single-source entries: P (44)

Each of these 14 subjects appears in only one of the 6 encyclopedias on this shelf. None is long enough to carry a page by itself, so they are gathered here by letter. Anything that grows moves out to a page of its own.

Phorcys

He is represented as a monster with one eye in the middle of his forehead. Ulysses was his captive, but escaped by putting a fire-brand in the monster's eye.

Only in 1000 Classical Characters

Phosgene

carbon oxychloride, carbonyl chloride, chlorocarbonic acid, CO Cl2. A colorless liquid, occurring as a trichloride gas at ordinary temperatures. Boiling H3PO3 + point 8.2 C., specific gravity 1.432 at 0 ° it forms C. Soluble in acetic acid and benzine. In phosphoric acid. contact with moisture it decomposes, forming carbon dioxide and hydrochloric acid. CO Cl2 + H2O = CO2 + 2 HCl Combines with ammonia to form urea and ammonium chloride. Prepared by passing carbon monoxide and chlorine through charcoal with or without a catalyst. It is a very poisonous, asphyxiating gas at temperatures tures above its boiling ling point, and this property was made use of in the World War, phosgene being used as a filling for shells, usually in combination with other gases. It is also used for bleaching sand employed in and in the preparaglass manufacture, re, tion of dye stuffs.

Only in Collier's New Encyclopedia

Phosphate

in chemistry, the generic term for the salts formed by the union of phosphoric anhydride with bases or water or both. They play a leading part in the chemistry of animal and plant life, the most important in this connection being the phosphate of soda, phosphate of lime, and the basic phosphate ate of magnesia. In agriculture the to plants preparation adequate supply of phosphates to in the form of manures becomes a matter of necessity in all deplenished soils. These phosphatic manures consist for the most part of bones, ground bones, mineral phosphates, bone ash and phosphatic guano. and death.

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Phosphorescence

the property which many substances and organic beings possess of emitting light under cer- Among tain conditions animals;, also some a phosphoric of Cuvier's light sub-. light. The changes kingdom Radiata have the power of emit- composition ting light in the dark, and the phos- be brought the early part phorescence of the sea in tropical, and known, even at times in temperate climates, is the eighteenth attributed to a small infusorial animal- serving in cule. On land, of insects, some millipedes, the female glow-worm, and the fireflies, emit light. In the glow-worm the light is from the under side of the final segments of the abdomen.

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Phosphoric Acid

in chemistry, H3PO4, ortho-phosphoric acid, a tribasic acid formed by the action of nitric acid upon phosphorus, or by the hydration of phosphoric anhydride. It is given in a very dilute state in diabetes and scrofula.

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Phosphorite

a species of calcareous earth; a sub-species of apatite. It is an amorphous phosphate of lime, and is valuable as a fertilizer.

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Phosphorous Acid

in chemistry, H3PO3. Prepared by adding water to the of phosphorus, PCl3 + H2O = 3HCl. Heated in a close vessel, phosphoreted hydrogen and

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Photochemistry

that branch of science which deals with the chemical of fact that changes in the brought about by the agency or structure of matter can about by light has been of probably, since the century, Schultze ob- 1727, that silver chloride, when exposed to sunlight, changed from creamy white a to purplish brown. Generally speaking, the rate of chemical action is proportional to the intensity of the light, but the exact determination of the activity of light was first suggested by John W. Draper, of New York University, who measured the rate of com bination brought about by light in a mixture of hydrogen and chlorine. Later, Bunsen and Roscoe made use of a photographic film, measuring the time required to darken the film to a standard tint. The action of light is not confined to any particular wave length, but the most active are the violet and ultraviolet, or so-called actinic, rays. Red light is, for most practical purposes, inactive, and this fact is made use of in photographic dark rooms in which white light is excluded and red lamps or windows employed. The action of light produces on photographic plates and bromide papers an effect which is not immediately visible, but can be made so by further action of a chemical known as a developer.

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Photoelectrotype

a block made mainly with the aid of photography and of the electrotyping process, and which can be printed with type like a woodcut. A photographic negative of the subject required is printed on a film of gelatine which has been treated with bichromate of potash, to render it sensitive to the action of light. Those parts on which the light has not acted are soluble in water, and are washed away, leaving the printed parts that are insoluble in relief. From this relief a mold is taken, and an electrotype made in the usual way. Unless special means are taken to translate the half-tones of the photograph into line or stipple, this process is only available for reproducing drawings, etc., in black and white.

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Photographs

TRANSMISSION. (See TELEPHOTOGRAPHY.)

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Photogravure

a term applied to methods of producing, by photography, plates for printing in a copper plate press. The processes are kept secret.

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Photophobia

a dread or intolerance of light; a symptom more or less present in all inflammations of the eye. It is also met with in many diseases of the nervous system and in many febrile conditions. luminous envelope believed to completely

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Photosphere

in astronomy, a surround the sun within an outer environment of a dense atmosphere. It is from the photosphere that light and heat are radiated. Used more rarely of the fixed stars.

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Photostat

a trade name for direct photographing process. By this means copies of drawings, legal papers, records, etc. may be rapidly produced. A special camera, with special developing and fixing attachments, is used in the process. The reproductions are made directly upon the surface of the print paper, which has been coated with a special emulsion. In order that the image will not be reversed the camera is fitted with a reversing prism and a special copying lens. The entire apparatus of the camera and developing plant is self-contained. After exposure the paper passes through the developing and fixing process, and is then cut and dried and is ready for use. The ordinary photostat print is white upon a black background, but by a slight addition to the process, black prints upon light backgrounds are secured. The process is much used for legal work, duplicating policies, in insurance, and particularly in engineering work, where many copies of the same plans are desired. The scale of the drawing made may be easily altered.

Only in Collier's New Encyclopedia