PHOSPHORESCENCE 



PHOSPHORUS 



145 



in them we may fairly regard it as a warning 

 signal, and it may have l>een adopted by stingless 

 forms for the same purpose by mimicry ; (c) it may 

 serve to attract prey, as in the phosphorescent lure 

 of the deep-sea angler-fish ( Melanocetus, &c.) ; (d) 

 it may illuminate the surrounding regions and 

 enable the light-producing animal to find its way, 

 as in Pyrophorus, Nyctiphanex, and many deep-sea 

 li-h. So many deep-sea animals are possessed of 

 luminous qualities that it has lieen assumed that 

 these living lights play an important part in the 

 economy of life in those regions ; this hypothesis is 

 commonly known as the 'abyssal theory of light.' 

 See the articles FIKEFLV, GLOW-WORM, and works 

 there cited. 



Phosphorus (sym. I': atom. wt. 31 ; molec. 

 wt., vapour = P 4 = 124 ; do. at white heat, P 2 = 

 62) is OIK; of the metalloids or non-metallic elements, 

 although, in its combining relations, it is closely 

 connected with the metals arsenic and antimony. 

 This snlwtance affords an excellent example of 

 Allotropy (q.v.); that is to say, it may be made 

 to occur under different forms presenting different 

 properties. Ordinary phosphorus and the red 

 \anety are the only important forms. We shall 

 s]>eak of them as phosphorus and red phosphorus 

 respectively. 



Phosphorus at ordinary temperatures is an almost 

 colourless or faintly yellow solid substance of sp. 

 gr. 1*836, having the glistening appearance and the 

 consistence of wax, and evolving a disagreeable 

 alliaceous odour, which, however, is probably due 

 to the action of the oxygen of the air upon it. It 

 fuses at 44-2 C. (111*5 F.) into a colourless fluid ; 

 and, if the air be excluded, it boils at 290 C. ( 554" F.), 

 and is converted into a colourless vapour of sp. gr. 

 4 *3f> (air =1-00). If, however, it be heated to 

 alxmt 60 C. (140' F.) in the air it catches fire, 

 burns with a brilliant white flame, and is converted 

 into phosphoric anhydride; and indeed it is so inflam- 

 mable that it will catch tire at ordinary temperatures 

 by mere friction. As the bums which it occasions 

 are often severe and dangerous, great caution is 

 required in handling it ; anil in consequence of the 

 readiness with which it catches fire, and of its 

 tendency to oxidise when expose.! to the air at a 

 temperature higher than C. (32' F.), it is always 

 kept in water, in which it is insoluble. It is slightly 

 .soluble in ether, but dissolves freely in benzol, in 

 the fixed and essential oils, ami in bisulphide of 

 carlxin ; and, on allowing its solution in a volatile 

 .solvent to fall upon filtering pa|>er, the finely - 

 divided phosphorus absorbs oxygen so rapidly as 

 spontaneously to catch fire as soon as the solvent 

 has evaporated. Phosphorus shines in the dark 

 from the slow combustion which it undergoes ; and 

 hence its name, from the Greek words /,/nj.i, ' light,' 

 tadpkorof, 'bearing.' Ite power of forming ozone 

 is noticed in the article on that substance. Taken 

 internally, phosphorus is a very powerful irritant 

 poison ; ami it is the active ingredient of some of 

 the preparations employed for the destruction of 

 vermin. Its fumes give rise to a peculiar form of 

 necrosis of the jaw and to fatty degeneration of the 

 kidney, which used to be common amongst the 

 makers of lucifer matches. 



Red phosphorus is prepared from the ordinary 

 variety by heating the latter in a closed iron vessel 

 to a temperature of 240" C. (464 F.). It was dis- 

 covered by Schriitter in 1845, and is a compact 

 -olid sill-stance of a dark red colour, and with a 

 metallic lustre. It differs much in its properties 

 from common phosphorus, l>eing devoid of odour, 

 does not shine in the dark, undergoes no change 

 when exposed to the air even for years, and cannot 

 be set on fire by moderate friction or percussion. 

 Moreover, it is insoluble in all the solvents of 

 common phosphorus, and is not poisonous. It l>ears 

 374 



heating to nearly 260 C. (500 F.) without taking 

 fire, and has a specific gravity of 2-16. By using 

 red instead of white phosphorus for lucifer matches 

 there is no risk to the health of the operatives. 

 Safety matches contain chlorate of potash and 

 ignite on a surface containing a mixture of 

 red phosphorus and sulphide of antimony (see 

 MATCHES ). 



Phosphorus is not met with in nature in an 

 uncombined state ; but it occurs in rocks of various 

 kinds and ages, and in some countries abundantly 

 as apatite or phosphorite, both of which are com- 

 posed of phosphate of lime. It is also found in the 

 form of Coprolites (q.v. ), or the dung of extinct 

 animals, and more rarely as wavellite (phosphate 

 of alumina) and vivianite (phosphate of iron). 

 In many volcanic rocks apatite is found in minute 

 crystals or particles, and by the decomposition of 

 these rocks it passes into the soil. From the 

 soil it is extracted by plants, which accumulate it 

 (especially in the seeds of the cereals) in quantity 

 sufficient for the wants of the animals which they 

 supply with food. In the animal system phosphate 

 of lime forms 57 |>er cent, of the bones ; phosphates 

 of the alkalies, especially of soda, occur freely in 

 the animal fluids ; and in fibrine, albumen, and 

 nervous matter phosphorus is universally present, 

 although we do not clearly know in what form 

 of combination it occurs. 



Phosphorus was originally discovered in 1669 by 

 Brandt, a Hamburg chemist, who obtained it from 

 urine. Gahn and Scheele were, however, the first 

 to discover its presence in bone, and to employ 

 that material for its preparation. The following are 

 the leading steps of the method now usually em- 

 ployed in obtaining it on the large scale. Bones are 

 Darned to whiteness, and powdered ; and this Ixme- 

 ash is then mixed with sulphuric acid in such quan- 

 tity as to decompose the phosphate of lime occurring 

 in the ash, Ca 3 (PO < ).,, partly into insoluble suH 

 pliate of lime, partly into a soluble superphosphate 

 of lime, whose composition is represented by the 

 formula H 4 Ca(PO 4 )j. The solution of the super- 

 phosphate is evaporated to a syrup, mixed with 

 charcoal, and submitted to distillation in an earthen 

 retort exposed to a red heat. Phosphorus rises in 

 vapour, and is conveyed by means of a l>ent tube 

 into water, in which it condenses in yellow drops. 

 Two distinct processes take place within the retort. 

 The first consists in the decomposition of the super- 

 phosphate of lime into bone-earth and hydrated 

 phosphoric acid ; while the second consists in the 

 deoxidation, by means of the carbon, of the 

 liberated phosphoric acid into phosphorus a process 

 accompanied by the evolution of carbonic oxide 

 gas. After being pressed in a fused state through 

 wash-leather, and farther purified, it is forced into 

 tulics, in which it is allowed to solidify, giving it 

 the usual form of sticks. Sombrerite (see APATITE) 

 is now largely substituted for bones in the manu- 

 facture of phosphorus. 



Phosphorus forms two known oxides phosphor- 

 ous anhydride, PjO*, obtained by the slow oxidation 

 of phosphorus in dry air ; phosphoric anhydride, 

 P,O 5 , obtained by the combustion of phosphorus in 

 an excess of dry air or oxygen. The latter is a snow- 

 like sulmtance which has a great avidity for water, 

 and is therefore very useful in the laboratory as a 

 desiccating agent. 



Phosphorus forms five acids hypophosphorous 

 acid, H'PHjOj, monobasic ( the anhydride, P S O, is 

 not known); phosphorous acid, H 2 'PHO 3 ( = P a O 

 4- 3H.O), dibasic, obtained by slow oxidation or 

 phosphorus in moist air or by passing chlorine gas 

 through phosphorus under hot water ; metaphos- 

 phoric acid, HPO 3 ( = P,O ? + H 2 O), monobasic, 

 obtained by dissolving PjO B in water or by heating 

 ordinary phosphoric acid to redness ; pyrophos- 



