PHOSPHORUS. 



PHOSPHORUS. 



,c acidi produced are so exceedingly deliquescent that 

 prepared with amorphous phosphorus are liable to become 

 damp. 



JUark PkvfJtortu if another amorphous variety of this element. 

 It U obtained by very suddenly cooling melted phosphorus. 

 The equiTalent of phosphorus is 32. 



Oxygr ad Pkatfikortu combine with great rmdineas, and form 

 four distinct compounds, namely : 



1. Oiidt of ptio]ihoru- 



3. Hypophu*phorou acid 

 S. Pho.phorou.tcia . 



4. 1'hu.phoric Kid . . 



P.O 



I'O 



!(., 

 I'O. 



1. QxiJe of PluBfAom. This is prepared by melting phosphorus 

 in hot water, and in this state forcing a jet of oxygen gas upon it. Tho 

 phosphorus burns under water, and the results are phosphoric acid, 

 which remains in solution, and which we shall presently describe, and 

 a red pulverulent body, which remains at the bottom of the vessel, and 

 is the oxide of phosphorus. It is inodorous and tasteless, and is 

 insoluble in water, alcohol, ether, or oil It undergoes no change in 

 the air, even when heated to above 600* Fahr. ; but at a low red heat 

 it burns. In chlorine gas it inflames. It decomposes nitric acid 

 readily, and combining with its oxygen, becomes phosphoric acid. It 

 does not possess either acid or alkaline properties. 



2. Jfypo^kotphania Acid was discovered in 1816 by M. Dulong. 

 When phosphide of barium is acted upon by water, both suffer decom- 

 position, and there are formed phosphuretted hydrogen, phosphoric 

 acid, hypophoephorous acid, and baryta ; the earth combines with both 

 the acids, and the phosphate of baryta being insoluble, is precipitated, 

 while the bypophoephite is soluble, and sulphuric acid being added to 

 the solution, sulphate of baryta is precipitated, and free hypophos- 

 phorous acid remains in solution ; by evaporating this, a viscid strongly 

 acid substance is obtained, which is bydrated hypophosphorous acid. 



Hypophosphorous acid is liquid, uncrystallisable, has a powerful 

 taste, is heavier than water, and cannot be obtained in a dry state. 

 When subjected to the action of heat, it is quickly decomposed into 

 phosphuretted hydrogen gas, which escapes, and phosphorous and 

 phosphoric acids. Water dissolves this acid in all proportions ; it acts 

 very powerfully as a deoxidising agent, but nevertheless combines with 

 many salifiable bases, forming salts which are termed hypophosphitet ; 

 these salts are remarkably soluble in water; they are usually deli- 

 quescent, and crystallise with great difficulty. From the circumstance 

 that neither thin acid nor its salts can be obtained free from water, 

 its true formula is probably PH,0,, that is phosphoric acid in which 

 two atoms of oxygen are replaced by two of hydrogen. 



3. Phosphorous Acid, like the preceding, is entirely an artificial 

 product ; it is obtained in the greatest purity by subliming phosphorus 

 through bichloride of mercury in a glass tube. During the action of 

 the heat, the phosphorus takes half the chlorine from the mercury, 

 and they form a volatile compound which condenses into limpid liquid 

 chloride of phosphorus: when this is mixed with water, mutual 

 decomposition occurs ; the hydrogen of the water and the chlorine of 

 the chloride form hydrochloric acid, while the oxygen and phosphorus 

 unite to form phosphorous acid. By evaporation the hydrochloric acid 

 is expelled, and when evaporation has been continued until the residue, 

 while hot, has the consistence of a syrup, it becomes a solid crystalline 

 mass on cooling, which is hydrated phosphorous acid. Thin acid 

 dissolves very readily in water, has a sour taste, reddens vegetable 

 blue colours, and combines with some bases to form salts, which 

 are called pkotpkitn. 



Phosphorous acid U also formed when phosphorus is burnt in 

 rarefied air. When phosphorus is exposed to air and moisture, it has 

 been long known that a dense sour fluid is formed by the absorption 

 of oxygen : this was supposed by M. Dulong to be a peculiar acid, and 

 he called it phosphatic acid ; it was however subsequently shown by 

 Davy to be a mixture of phosphorous and phosphoric acids. 



Photphilt of Ammonia U procured by adding carbonate of ammonia 

 to the acid to saturation. It crystallises in deliquescent needles ; when 

 heated, it is decomposed, giving out ammonia ; and by the continued 

 application of heat, the phosphorous acid remaining is converted into 

 phosphoric acid. It is not a salt of any importance. 



4. Pkofpkone Add. Thin acid exists largely in nature, not only, as 

 has been already mentioned, in combination with lime, forming bone, 

 but also In some vegetable products, and often in the bowels of the 

 earth, combined with lime, forming a mineral which, when crystallised, 

 is frequently called apatilt. [See also PHOSPHATITK, in NAT. HIST. 

 Div.J It also occurs in combination with oxide of iron, copper, lead, 

 msngsnese, and uranium ; but the quantity of thete compounds is by 

 no means large, and they are regarded chiefly as objects of curiosity. 



Pluifpkarie Arid may be artificially formed by the direct combination 

 of iu element*. When a piece of phosphorus Is inflamed, and imme- 

 diately covered by a large bell glass, white flakes of phosphoric acid 

 are produced, which fall like snow in the vessel. When exposed for a 

 hort time to the air, the acid deliquesces. So great is its affinity for 

 water, that when collected, and a little water added to it, it is converted 

 into a hydrate with explosive ebullition, owing to the heat which is 

 evolved during combination. Phosphoric acid, when free from water, 



may be volatilised in a glass tube by the heat of a spirit-flame ; the 

 hydrate U even more readily dissipated. 



Phosphoric acid U also formed when phosphorus is healed in mode- 

 rately strong nitric acid; the nitric acid U decomposed, and yields 

 oxygen to form the phosphoric acid. By evaporation in a plutina 

 capsule, hydrated phosphoric acid is obtained. 



Phosphoric acid is colourless, inodorous, dense, extremely sour to 

 the taste, and acts strongly on vegetable blue colours ; it does not, 

 however, like sulphuric acid, destroy the skin when applied to it. 

 Phosphoric acid is peculiarly disposed to combine with different pro- 

 portions of water, and these compounds exhibit properties so different, 

 that they might be supposed to be three different acids, instead of 

 different hydrates of the same acid. When the dry acid, obtained as 

 described from the combustion of phosphorus, is thrown into water, a 

 mixture of the three hydrates is obtained in variable proportions ; but 

 they may be separately obtained in a pure state from the common 

 phosphate of soda of the shops, after it has been purified by 

 solution and recrystalliaation. Decompose a warm solution of this 

 salt by means of a solution of acetate of lead, and wash the precipi- 

 tated phosphate of lead, and then pass a current of hydrosulphuric 

 acid through it while suspended in water. When the excess of hydro- 

 sulphuric acid has been expelled by heat, a very sour fluid remains, 

 which is a terhydrale of photphoric acid (3HO, PO,). 



This terhydrated acid is unalterable by boiling its solution or 

 keeping it for any length of time. The class of salts which it forms 

 are phosphates, which give a yellow precipitate with nitrate of silver 

 (SAgO, PO,). Common phosphate of soda contains, therefore, this 

 terhydrated phosphoric acid. 



Pyrophosphoric Acid. Professor Clark, of Aberdeen, first discovered 

 that when common phosphate of soda is heated to redness, it is com- 

 pletely changed in some of its properties, and after being dissolved in 

 water, it affords crystals of a new salt, which he named pyrophotphatt 

 of loda (2NaO, P0 5 ). It gives a white precipitate with nitrate of silver 

 (2AgO, PO,), instead of a yellow one. If a solution of this salt be 

 decomposed by one of acetate of lead, and the precipitated phosphate 

 of lead be treated with hydrosulphuric acid as already described, and 

 then evaporated iu vacuo, over sulphuric acid, without the application 

 of heat, the remaining solution is pyrophosphoric acid, consisting of 

 2HO, P0 5 . 



Sfetaphosphoric Acid. If equivalent proportions of ordinary phos- 

 phate of soda (2NaO, HO.PO,) and terhydrated phosphoric acid (3HO, 

 I'O,) be evaporated to dryness.a tribasic phosphate of soda U obtained, 

 containing (NaO,2HO, P0 a ), and this, on being treated as the last, 

 gives an acid liquor, containing the metaphosphoric or monohydrated 

 phosphoric acid (HO, PO.). 



Glacial phosphoric acid is also in general mostly metaphosphoric 

 acid. This hydrate is characterised by producing a white precipitate 

 in solution of albumen, and in solutions of the salts of earths and 

 metallic oxides ; precipitates which are remarkable semifluid bodies, or 

 soft solids without crystallisation. 



JJydrogen and Phosphorus combine in three different proportions. 

 When phosphide of calcium is thrown into hot water containing hydro- 

 chloric acid, a yellow powder precipitates, which is a solid phosphide 

 of hydrogen, containing P B H. 



Phosphuretted Hydrogen Gat (PH a ). This gas was obtained by 

 Gengembre in 1783 : it is procured by boiling phosphorus in a solution 

 of potash, or in small quantity on bringing phosphide of calcium into 

 contact with water. The gas which arises is spontaneously inflam- 

 mable ; and during its combustion there are formed water and phos- 

 phoric acid : it is colourless, and has a disagreeable odour resembling 

 that of onions. Water dissolves about two per cent, of this gas ; but 

 the solution, unlike that of sulphuretted hydrogen gas, has no acid 

 properties. It deposits solid phosphuretted hydrogen when exposed 

 to light. The specific gravity of this gas, according to Dumas, is 1761. 

 Its spontaneously inflammable property is due to the presence of liquid 

 phosphurMed hydrogen (PH 2 ). The latter may be separated by passing 

 the freshly-made gas through a tube immersed in a freezing mixture. 

 It burns explosively when exposed to the air, and renders hydrogen, 

 carbonic oxide, &c., spontaneously inflammable. 



Phosphuretted hydrogen gas decomposes some metallic solutions, 

 such as those of copper and mercury, and metallic phosphides are pre- 

 cipitated. When it is pure, it is entirely absorbed by sulphate of 

 copper and chloride of lime. 



Chlorine and Phosphorus combine in two proportions, forming the 

 pentacbloride and terchloride. 



Tenhloride of Pluaphonu (PCI,). When a mixture of bichloride of 

 mercury and phosphorus is heated, we have already had occasion to 

 notice that terchloride of phosphorus is produced. When first pro- 

 cured, it has generally a reddish colour, owing to the presence of a 

 little uncombined phosphorus. When this has had time to deposit, or 

 when it U purified by slow distillation, it becomes limpid and colour- 

 less. It has a suffocating odour, and fumes when exposed to the air. 

 Its specific gravity is 1'616. It does not alter the colour of dry litmus- 

 paper; but if moist, then hydrochloric and phosphorous acids are 

 formed, which redden it strongly. The vapour of this compound is 

 combustible, and acts with great energy upon water, producing the 

 changes which have been described. 



Pentathliride of PhrajJiw* (PClj) is obtained by the spontaneous 



