Page:Encyclopædia Britannica, Ninth Edition, v. 18.djvu/852

 816 PHOSPHORUS vapour they are being provided with two or three coats of some kind of cement, such as a mixture of slaked lime and borax, or a magma of clay, horse-dung, and water. In the collecting and further manipulation of the phosphorus the dangerous inflammability of the substance demands that all operations be conducted under water. As soon as the retorts have cooled down sufficiently the condensers are detached and their tubuli bunged up to prevent access of air to the inside. The necks of the retorts are knocked off and thrown into water to save the phosphorus which has condensed within them and to unite it with that of the condensers. From the analysis of the ox-bone quoted we calculate that its ash contains 17 6 per cent, of phosphorus, of which two-thirds ( = 11&quot; 7 per cent.) should be recoverable as free phosphorus ; according to Fleck, the yield of phosphorus is 8 per cent., while Payen puts it down at 8 to 10 per cent. But this crude phos phorus is largely contaminated with blown-over bone-ash and charcoal and with &quot;red&quot; phosphorus. Its purifica tion used to be effected everywhere by melting it under water of about GO 3 C., and pressing it through chamois leather by means of a force-pump. In certain French works porous fireclay serves as a filtering medium, while superheated steam supplies at the same time the necessary heat and pressure. By the addition of coarsely-powdered charcoal to the phosphorus the clogging-up of the pores of the fireclay septum is precluded. A more effectual method of purification is to re-distil the crude (or perhaps the previously filtered) phosphorus from out of cast-iron retorts, the necks of which dip half an inch deep into water contained in a bucket. A chemical method of purification is that of Bottcher, who fuses the crude phos phorus (100 parts) under water, with addition of 3 5 parts of oil of vitriol and 3 5 parts of bichromate of potash. The phosphorus passes, with a feeble gas-evolution, into an almost colourless liquid, with a loss of only 4 per cent. of its weight, as against the 10 to 15 per cent, unavoid ably involved in the distillation process. To bring the purified phosphorus into the traditional form of sticks it is fused under water and sucked up into slightly conical glass tubes about two-fifths of an inch wide and a foot long; the tubes are closed below with the finger and immersed in cold water to cause the contents to freeze. The solid stick is then pushed out by means of a rod, and cut into pieces with a pair of scissors. For emission into commerce the sticks are put into cylindrical wide-necked glass bottles, or into tin canisters, full of water, which latter had better be mixed with a sufficiency of alcohol or glycerin to prevent freezing (and bursting) in winter time. Seubert, about 1&44, invented an ingenious apparatus for the continuous casting of phosphorus-sticks, consisting of a funnel-shaped vessel of copper, terminating below in a long horizontal copper tube, the outer end of which lies within a tank full of cold water. The phosphorus is placed in the funnel, covered with water, and the whole up to the cold-water tank raised (by means of a w 7 ater-bath and steam-pipes) to a suitable temperature, matters being ar ranged so that the phosphorus freezes just on. arriving at the exit end of the tube. The workman then catches the protruding button of phosphorus and pulls out an endless stick, which is cut up into pieces of the desired length. This ingenious apparatus, however, has not been found to work satisfactorily, and has been given up again in favour of some form of the old method. The loss of one-third of the phosphorus contained in the bone-ash, which is unavoid ably involved in the ordinary method of phosphorus- making, can be avoided, according to Wohler, by adding finely-powdered quartz to the mixture which goes into the retorts. The superphosphate is then completely decom posed with formation of a residue of silicate, instead of phosphate, of lime. An improvement by Fleck aims at the utilization of the organic part of the bones. He pro poses to recover the fat from the bones by boiling them with water and then the gelatin by digesting them in hydrochloric acid of 1*05 specific gravity. The gelatin remains in a coherent form ; the phosphate passes into solution as mono-calcic salt, which is recovered by evapora tion in crystals and then reduced by distillation with charcoal. None of these (and other) proposals have been much heeded ; the manufacture of phosphorus at present, in fact, is almost a monopoly, the bulk of what occurs in commerce being produced by two firms, viz., Albright and Wilson of Oldbury, near Birmingham, and Coignet and Son in Lyons. According to E. Kopp, the production in 1874 amounted to 1200 tons. Recently purified phosphorus is a slightly yellowish or colpmiess solid of about the consistence of beeswax. At low temperatures it is brittle; specific gravity == 1 83 at 10 C. It fuses at 44 3 C. into a strongly light-refracting liquid of 1 743 (Kopp) specific gravity. Neither in the solid nor in the liquid state does it conduct electricity. When heated further (in an inert atmosphere such as hydrogen or carbonic-acid gas) it boils at 290 C., and assumes the form of a colourless vapour which at 1040 C. is 4&quot; 5 times as heavy as air or 65 1 times as heavy as hydrogen, whence it follows that its molecular weight is 2 x 65 1 = 130 - 2 = very nearly four times the atomic weight of phosphorus (31 0). Phosphorus is insoluble in water, more or less sparingly soluble in alcohol, ether, fatty oils, and oil of turpentine, and very abundantly soluble in bisul phide of carbon. When exposed to the air, and especially to moist air, it suffers gradual oxidation into phosphorous and phosphoric acids with evolution of a feeble light. Phos phorus does not phosphoresce in the absence of oxygen. Singularly, it does not phosphoresce in pure oxygen either, unless the tension of the gas be reduced to some point considerably below one atmosphere (Graham). Phosphorus is a most dangerous poison ; doses of as little as 1 gramme ( = 1 5 grains) are known to have been fatal to adults. The heads of a few lucifer matches may suffice to kill a child. Phosphorus is used chiefly for the manu facture of lucifer matches (see MATCHES, vol. xv. pp. 625, 626) and also in the manufacture of iodide of methyl and other organic preparations used as auxiliary agents in the tar-colour industry. Phosphorus-paste, made by working up a small proportion of phosphorus melted under water in a hot mortar with flour, is used as poison for vermin. Red Phosphorus. A red infusible solid which is always produced when ordinary phosphorus is made to burn in an insufficient supply of air, and also by the long-continued action of sunlight on phosphorus-sticks kept under water, used to be taken for a lower oxide of the element, until A. v. Schrbtter of Vienna showed, in 1 845, that it is nothing but an allotropic modification of the elementary substance. A given mass of ordinary phosphorus can be converted almost completely into the red modification by keeping it at 240 to 250 C. in the absence of air for a sufficient time. The addition of a trace of iodine to phosphorus at 200 C. brings about the conversion suddenly with large evolution of heat (Brodie). Red phosphorus is now an article of chemical manufacture. The phos phorus is simply heated, and kept at the requisite temperature, within a large iron pot which communicates with the atmosphere by only a narrow pipe. At a very slight expense of the material the air within the apparatus is quickly deoxygenated and con verted into (inert) nitrogen. The requisite steady temperature is maintained by means of a bath of molten solder. By the mere effect of the heat the phosphorus becomes more and more viscid and darker and darker in colour, and is at last completely con verted into a dark -red opaque infusible solid. This, however, always includes a small proportion of the ordinary modification, which is most readily extracted by powdering th&quot; crude product and exhausting it with bisulphide of carbon, which does not affect the red kind. A less expensive method is to boil the powdered raw product with successive quantities of caustic-soda ley, when the ordinary phosphorus only is dissolved as hypophosphito with evolution of phosphurctted hydrogen. The residue is washed and