[91] ‘Chemical News.’
PAPY′RIN. See Paper (Parchment).
PAR′ACHUTE. In aërostation, an instrument or apparatus having for its object to retard the descent of heavy bodies through the air. The only form of parachute which has been hitherto adopted with success is that of the common umbrella when extended. The materials of which the apparatus is made are canvas and cord, both light but strong, and carefully put together. The car to contain the adventurer resembles that of the balloon, only smaller.
It is estimated that a circular parachute, to descend in safety with an adult, weighing, with the apparatus, 225 lbs., must have a diameter of at least 30 feet. Its terminal velocity would then be at the rate of 12 to 13 feet per second, or about 61⁄2 miles per hour; and the shock experienced on contact with the earth would be equal to that which the aëronaut would receive if he dropped freely from a height about 21⁄2 feet.
Several descents from balloons, after they have acquired a great elevation, have been effected without accident by means of parachutes. Unfortunately, however, any want of integrity in the machine, or any accident which may happen to it after its detachment from the balloon, is irreparable and fatal.
PARACYAN′OGEN. The brown solid matter left in the retort when cyanide of mercury is decomposed by heat. It is isomeric with cyanogen.
PARAFFIN. Syn. Tar-oil stearin. This remarkable hydrocarbon is one of the several substances discovered by Reichenbach in WOOD-TAR.
Prep. 1. (From WOOD-TAR. Reichenbach.) Distil beech-tar to dryness, rectify the oily portion of the product which is heavier than water until a thick matter begins to rise, then change the receiver, and moderately urge the heat as long as anything passes over; next digest the product in the second receiver, in an equal measure of alcohol of ·833, gradually add 6 or 7 parts more of alcohol, and expose the whole to a low temperature; crystals of paraffin will gradually fall down, which, after being washed in cold alcohol, must be dissolved in boiling alcohol, when crystals of pure paraffin will be deposited as the solution cools.
2. (From COAL—James Young, Patent 1850.) The details of this process for obtaining paraffin and its congeners by the slow distillation of coal (preferably ‘Boghead’) are given in our article on PARAFFIN OIL. The solid paraffin is separated from the last products, or ‘heavy oils,’ by artificial cold; it is then melted and run into moulds.
3. (From Rangoon petroleum—Patent.)