CHAMBERS'S INFORMATION FOR THE PEOPLE. 



about three times its volume of the gas. It has 

 an extremely unpleasant smell, like that of rotten 

 eggs, and acts as a poison upon animals and 

 plants. It is inflammable, burning in air or 

 oxygen with a blue flame, and producing water 

 and sulphurous acid gas. It is most conveniently 

 prepared by the action of dilute sulphuric acid on 

 ferrous sulphide (FeS+H 2 SO 4 =H 2 S+FeSO 4 ). It 

 acts upon many metallic salts, producing a metallic 

 sulphide and a hydrated acid, thus : 



CuO,SO 3 + H S S = H 8 O,SO 3 + CuS. 



Sulphate Sulphuretted Hydrated Cupric 



of Copper. Hydrogen. Sulphuric Acid. Sulphide. 



All metallic salts are not thus acted on, and this 

 difference of behaviour is taken advantage of in 

 separating the metals from one another. 



Sulphur unites with carbon when sulphur-vapour 

 is passed over red-hot charcoal, forming bisul- 

 phide of carbon (CS 2 ), a very volatile liquid, used 

 as a solvent of sulphur, phosphorus, and oils and 

 fats. It is very easily set fire to, and burns with 

 a blue flame, forming carbonic acid and sulphurous 

 acid. As will be seen from its formula, it cor- 

 responds to carbonic acid (CO 2 ) ; and just as car- 

 bonic acid unites with basic oxides to form car- 

 bonates (such as Na^jCOg), so bisulphide of 

 carbon unites with the sulphides of positive metals 

 to form J7^//0-carbonates (such as NagSjCS^. 



PHOSPHORUS is an element very widely diffused 

 in nature. Compounds of phosphorus are essential 

 ingredients in every fertile soil, are absorbed by 

 plants, and pass from plants into animal bodies. 

 The animal tissues containing large quantities of 

 phosphorus are the bones, and the nervous tissues, 

 brain, spinal cord, nerves. Phosphorus can be 

 obtained in two 'allotropic' modifications : i. 

 Common, yellow, or waxy phosphorus a trans- 

 lucent yellowish solid of specific gravity 2. It 

 fuses at 112 F. and boils at 550 F. It unites 

 slowly with oxygen at ordinary temperatures, and 

 shines in the dark when exposed to air. It is 

 very easily inflammable, taking fire when moder- 

 ately warmed in the air, so that it is dangerous 

 to handle it, and it ought to be preserved under 

 water. It is extremely poisonous, and serious and 

 even fatal accidents have occurred from children 

 sucking the ends of lucifer-matches containing 

 phosphorus. 2. Red or amorphous phosphorus 

 is produced from common phosphorus by keeping 

 it for a long time at a temperature slightly below 

 its boiling-point. It is a red solid, and differs very 

 much in character from common phosphorus. It 

 is not fusible; it is not readily inflammable; it is 

 not poisonous. When heated to the boiling-point 

 of common phosphorus, it is changed back into the 

 latter, and therefore takes fire if heated to this 

 temperature in the air. 



Compounds of Phosphorus and Oxygen. Phos- 

 phorus combines with oxygen in two proportions, 

 forming, first, anhydrous phosphorous acid (P 2 O 3 ), 

 and second, anhydrous phosphoric acid (P 2 O 5 ). 

 We shall here consider only the latter. When 

 phosphorus is set fire to in air or oxygen, it burns 

 with dazzling brilliancy, forming anhydrous phos- 

 phoric acid. This is a snow-white solid, which 

 unites with the greatest readiness with water, 

 giving out much heat. It forms with water three 

 distinct hydrates or hydric salts : 



P 2 O 5 + H 2 O= H 2 O,P 2 O 5 Hydric AWaphosphate. 



P 2 O 5 + 2H 2 O = 2H 2 O,P. 2 O 5 Hydric -Py^phosphate. 



P 2 O 5 + 3H a O = 3H S O,P 2 O 5 Hydric < 



326 



If in these formulae we put all the oxygen 

 together, we find that the first and third are 

 divisible by two, so that we have the following 

 formulae : 



Hydric Metaphosphate (or Hydrated Metaphosphoric 



Acid) ........................................ HPOs, 



Hydric Pyrophosphate (or Hydrated Pyrophosphoric 

 Acid) ........................................ 



Hydric Orthophosphate (or Hydrated Orthophosphoric 

 Acid, usually called Common Phosphoric Acid) . . 



Corresponding to each of these hydrates, there 

 are series of salts ; thus, we have metaphosphate 

 of lime (CaO,P 2 O 6 ), metaphosphate of soda 

 (Na2O,P 2 O 5 ), metaphosphate of silver (Ag 2 O,P 2 O 5 ), 

 pyrophosphate of lime(2CaO,P 2 O 6 ), pyrophosphate 

 of soda (2Na 2 O,P 2 O 5 ), pyrophosphate of silver 

 (2Ag 2 O,P 2 O 5 ), orthophosphate (or common phos- 

 phate) of lime (3CaO,P 2 O 5 ), common phosphate 

 of soda (2NaO,H 2 O,P 2 O 5 ), common phosphate of 

 silver (3Ag 2 O,P 2 O5). It will be observed that in 

 common phosphate of soda we have, as in all 

 common, or ortho, phosphates, three equivalents 

 of base to one P 2 O 6 , but only two of these are 

 anhydrous soda, the other being water ; this salt 

 is, therefore, formally, an acid salt ; it has not, 

 however, an acid reaction, and the normal salt, 

 3NaO,P 2 O 5 , is an unstable, highly alkaline body. 

 When an orthophosphate, containing, as in this 

 case, basic water, is heated, water is given off, 

 and a pyrophosphate or metaphosphate is left ; 

 thus, when common phosphate of soda is heated, 

 water is given off, and pyrophosphate of soda is 

 left : 2Na2O,H 2 O,P 2 O 6 = H 2 O + 2Na 2 O,P 2 O 5 or 

 2Na2HPO 4 = H 2 O + Na 4 P 2 O r ; and when what is 

 called acid phosphate of soda (Na2O,2H 2 O,P 2 O 5 ), 

 which is also an orthophosphate, is heated, water 

 is given off, and metaphosphate of soda is 

 left : Na 2 O,2H 2 O,P 2 O 5 = 2H 2 O + Na 2 O,P 2 O 3 or 

 NaH 2 PO 4 =!H 2 O + NaPO 3 . 



Common phosphate of lime (3CaO,P 2 O 5 or 

 Ca 3 (PO 4 ) 2 ) is the most abundant mineral con- 

 stituent of bones ; and ' bone-ash,' the substance 

 left when bones are burned white in an open fire, 

 so as to destroy all the animal matters, consists 

 chiefly of this phosphate. When treated with 

 sulphuric acid and water, a partial decomposi- 

 tion takes place, which is represented by the 

 following equation : 3CaO,P 2 O 5 -f 2(H 2 O,SO 4 ) 

 = CaO,2H 2 O,P 2 O 5 + 2(CaO,SO 4 ). The sulphate 

 of lime (CaO,SO 4 ) being sparingly soluble in 

 water, settles for the most part to the bottom 

 of the vessel in which the decomposition is 

 effected, while the acid phosphate of lime (super- 

 phosphate) remains in solution. This superphos- 

 phate is largely used as a manure. When super- 

 phosphate of lime is heated, it loses water, and 

 leaves metaphosphate of lime : CaO,2H 2 O,P 2 O 5 = 

 2H 2 O + CaO,P 2 O 5 . From metaphosphate of lime, 

 phosphorus is obtained by heating it in earthen- 

 ware retorts with charcoal. Two-thirds of the 

 anhydrous phosphoric acid (P 2 O 5 ) are decomposed, 

 the charcoal taking the oxygen to form carbonic 

 oxide, and thus setting the phosphorus free, while 

 one-third remains with all the lime as common 

 phosphate of lime : 3(CaO,P 2 O 5 ) + xoC = loCO- 

 + 4 P + 3CaO,P 2 5 . 



Phosphuretted hydrogen, PH 3 , is a colourless, 

 transparent gas, having a disagreeable smell. It 

 may be formed by heating phosphorus in a strong 

 solution of caustic potash. As thus formed, it 

 is spontaneously inflammable, taking fire at once 

 on coming into contact with air or oxygen. The 



