PHOSPHORUS 557 



more general purposes. Some experiments have also shown that, combined with 

 alumina and a little boracic acid, it is capable of producing a glaze for earthen-ware 

 of extreme beauty and durability, in addition to its perfectly innocuous character and 

 - power of improving the colours imparted by most metallic oxides when applied to 

 earthenware." 



Another method of forming this monobasic acid is the following : one part of phos- 

 phorus is cut into small pieces, and introduced into a retort connected vrith a receiver, 

 and containing thirteen parts of nitric acid, sp. gr. 1-2. The retort is moderately heated 

 on a sand-bath, and the nitric acid which distils over returned to it from time to time 

 -until the phosphorus has disappeared. The greater part of the nitric acid is then 

 distilled off, and the residual liquor evaporated so long as any water is evolved upon 

 cooling : the phosphoric acid is a colourless glass, which dissolves slowly in water. 



PHOSPHORITE. Concretionary and massive apatite. See APATITE. 



PHOSPHORUS. (The following detailed description of the manufacture of 

 phosphorus is left in Dr. Ure's own words, it being a good example of his descriptive 

 powers when applied to scientific manufactures.) This interesting simple combustible 

 ' being an object of extensive consumption, and therefore of a considerable .chemical 

 manufacture, I shall describe the requisite manipulations for preparing it at some 

 detail. Put 1 cwt. of finely-ground bone-ash, such as is used by the assayers, into a 

 stoiit tub, and let one person work it into a thia pap with twice its weight of water, 

 and let him continue to stir it constantly with a wooden bar, while another person 

 pours jnto it, in a uniform but very slender stream, 78 Ibs. of concentrated sulphuric 

 acid. 



The heat thus excited in the dilution of the acid, and in its reaction upon the cal- 

 careous base, is favourable to the decomposition of the bone phosphate. Should tho 

 resulting sulphate of lime become lumpy, it must be reduced into a uniform paste, by 

 the addition of a little water from time to time. This mixture must be made out of 

 doors, as under an open shed, on account of the carbonic acid and other offensive gases 

 which are extricated. At the end of 24 hours the pap may be thinned with water, and 

 if convenient, heated, with careful stirring, to complete the chemical change, in a square 

 pan made of sheet-lead, simply folded up at the sides. Whenever the paste has lost 

 its granular character, it is ready for transfer into a series of tall casks, to be further 

 diluted and settled, whereby the clear superphosphate of lime may be run off by a 

 syphon from the deposit of gypsum. More water must then be mixed with the pre- 

 cipitate, after subsidence of which tho supernatant liquor is again to be drawn off. 

 The skilful operator employs the weak acid from one cask to wash the deposit in 

 another, and thereby- saves fuel and evaporation. 



The collected liquors being .put into a leaden, or preferably a copper pan, of proper 

 dimensions, are to be concentrated by steady ebullition, till the calcareous deposit 

 becomes considerable ; after the whole has been allowed to. cool, the clear liquor is to be 

 run off, the sediment removed, and thrown on a filter. The evaporation of the clear 

 liquor is to be iirged till it acquires the consistence of honey. Being now weighed, it 

 should amount to 37 pounds. One fourth of its weight of charcoal in fine powder, 

 that is, about 9 pounds, is then to bo incorporated with it, and the mixture is to be 

 evaporated to dryness in a cast-iron pot; A good deal of sulphurous acid is disen- 

 gaged along with the steam at first, from the reaction of the sulphuric acid upon tho 

 charcoal, and afterwards some sulphuretted hydrogen. When the mixture has be 

 come perfectly dry, as shown by the redness of the bottom of the pot, it is to be allowed 

 to cool, and packed tight into stoneware jars, fitted with close covers, till it is to be 

 subjected to distillation. For this purpose, earthen retorts of the best quality, and 

 free from air-holes, must be taken, and evenly luted over the surface with a compost 

 of fire-clay and horse-dung. -When the coating is dry and sound, the retort is to be 

 two-thirds filled with tho powder, and placed upon proper supports in the laboratory 

 of an air furnace, having its fire placed not immediately beneath the retort, but to one 

 side, after the plan of a reverbatory ; whereby tho flame may play uniformly round 

 the retort, and the fuel may be supplied as it is wanted, without admitting cold air to 

 endanger its cracking. The gallery-furnace of the Palatinate (see MEKCTJEY) will 

 show how several retorts may be operated upon together, with one fire. 



To the beak of the retort, properly inclined, the one end of a bent copper-tube is to 

 be tightly luted, while the other end is plunged not more than one quarter of an inch 

 beneath the surface of water contained in a small copper or tin trough placed beneath, 

 close to the side of the furnace, or in a wide-mouthed bottle. It is of advantage to let 

 the water be somewhat warm, in order to prevent the concretion of the phosphorus 

 in the copper-tube, and the consequent obstruction of the passage. Should the beak of 

 the retort appear to get filled with solid phosphorus, a bent rod of iron may be heated 

 and passed up the copper-tube, without removing its end from the water. The heat 

 of the furnace should be most slowly raised at first, but afterwards equably maintained 



