Glue, gelatine, animal charcoal, phosphorous, cements, pastes and mucilages

by F. Dawidowsky

Under certain conditions enameled cast-iron may be used as a material for receivers, but the enamel must be of such a nature as not to be attacked by the phosphorus vapors, otherwise the receivers would in a short time be destroyed.

The retorts having been filled with the required quantity of mixture are placed in the furnace and the brickwork is restored. The fire is then kindled and kept up very gently for some time in order to dry the fire clay used in joining the bricks. The receivers are filled with water and fitted to the retorts. In each receiver a small iron spoon is placed fastened to iron wire which serves as a stem. After six to eight hours of firing the heat has been so much increased as to cause the expulsion of any moisture left in the material placed in the retorts, while quantities of hydrocarbon gases and oxide of carbon are formed and expelled with the sulphurous acid. Subsequently other gases are given off, and because they contain some hydrogen phosphide are spontaneously inflammable. As soon as this phenomenon is observed the joints of the receivers and apparatus connecting it with the retorts are luted with clay, care being taken to leave, by the insertion of an iron wire, a small opening for the escape of the gases, which are as speedily as possible removed by well arranged ventilators from the building in which the furnace is placed. The appearance of amorphous phosphorus at the small opening indicates the commencement of the distillation.

The spoon is then placed in the receiver in such a direction that any phosphorus coming over may collect in it. During the progress of the operation, and as long as any phosphorus distils over, the evolution of combustible gases continues, and consequently a small blue-colored flame is observed at the opening in the lute. The water in the receiver is kept cool during the operation. After forty-six hours, with greatly-increased firing, a full white heat is reached, and the quantity of phosphorus coming over has decreased so much as to make a continuation of the ignition process wasteful. The receivers are therefore disconnected from the retorts.

The receivers are taken to a special room and entirely submerged in large wooden troughs filled with water in order to drive off inflammable gases still contained in them and to cover the phosphorus with water. They should be opened only after this has been done, and every manufacturer should rigidly enforce the rule of carrying on the operation in the above-described manner. Crude phosphorus is very inflammable, and when carelessly handled by the workmen may inflict horrible burns and, as the phosphorus as a rule causes blood-poisoning, such injuries generally cause death.

The phosphorus is then removed from the receivers (always under water). The trough in which this operation is effected should be provided, a few inches above the actual bottom, with a perforated false bottom upon which the receivers are placed. The larger pieces of phosphorus taken from the receivers are collected, under water, in special vessels, while the smaller pieces fall through the perforations of the false bottom to the actual bottom. When all the receivers have been emptied, the water in the trough is discharged into a large barrel in which it remains until the particles of phosphorus have subsided. The water is then drawn off, with the exception of a sufficient quantity to cover the phosphorus in the barrel.

The water from the receivers as well as from the troughs shows a quite strong acid reaction due to phosphoric acid, which has been formed by the combustion of phosphorus and passed into solution. In order not to lose this phosphoric acid, the water is partly used for filling the receivers and partly for mixing the bone-ash before adding the sulphuric acid.

Crude phosphorus is a mixture of crystalline (ordinary) phosphorus with amorphous phosphorus, the reddish color of the mass being due to the latter. It further contains phosphorus in various stages of oxidation, free carbon, and if impure sulphuric acid has been used, arsenic in combination with phosphorus.

Refining and purifying the phosphorus. The crude phosphorus was formerly purified by forcing it through the pores of stout wash leather by means of a machine. The crude phosphorus contained in a tightly tied piece of wash leather is placed on a perforated copper support situated in a vessel filled with water at 122° to 140° F. As soon as the phosphorus is molten, there is placed on the wash leather a wooden plate which by the aid of a mechanical arrangement and a lever can be forced downwards so as to cause the fluid phosphorus to pass through the pores of the leather, the impurities being retained. The phosphorus in the form of a slightly yellowish fluid collects on the bottom of the vessel and is immediately moulded into the shape in which it is brought into commerce. The residue in the wash leather consists chiefly of charcoal dust and amorphous phosphorus. The wash leather can, as a rule, be only used once, and only small quantities of phosphorus can be worked at one time.

A more suitable process of purification is as follows: Porous, unglazed porcelain or earthenware plates are fixed in an iron cylinder connected with a steam boiler. The cylinder having been hermetically closed is placed in a vessel containing water at 140° F. When the phosphorus is molten, steam of a few atmospheres’ pressure is admitted into the cylinder, the phosphorus being thus forced through the earthenware plates.

The phosphorus obtained by either of these methods is free from mechanically admixed particles of charcoal and amorphous phosphorus, but it is by no means pure, as all the substances dissolved in it (oxides of phosphorus) pass through the filter. The loss of phosphorus amounts to from 5 to 6 per cent. of the weight of the crude product. The masses taken from the filter plates are therefore collected and subjected by themselves to distillation in order to obtain the phosphorus contained in them.