PHOTOQEN 559 



pins. lu the interior iron pan a glass vessel is fitted, in which the phosphorus to 

 bo operated upon is placed. From this inner vessel a tube passes, and is dipped into 

 \vater to serve as a safety-valve. A spirit lamp is applied under that pipe if necessary, 

 to prevent it being clogged with phosphorus. The phosphorus to be converted is 

 first of all melted, and then cooled under water, and dried as much as possible. A fire 

 is now made under the other vessel, and the temperature raised to such a degree as to 

 drive off the air, &c. The temperature has to be gradually raised, until bubbles escape 

 :it the end of the pipe, which take fire as they enter the air, and the heat may soon 

 rise in the bath till it be 470 F. This temperature must be maintained for a 

 certain time to be determined by experience : the apparatus may then be allowed to 

 cool. The converted phosphorus is difficult to detach from the glass. It is to be 

 levigated under water, and then drained in a bag. The phosphorus when moist should 

 be spread thinly on separate shallow trays of sheet iron or lead, so placed alongside 

 each other as to receive the heat of steam, and lastly, of chloride of calcium, or of 

 sand, till the phosphorus, having been frequently stirred, shows no more luminous 

 vapour. The operator should have water at hand to quench any fire that might 

 arise. It is then to be washed till the water shows no trace of acid. Should the result- 

 ing phosphorus contain some of the unconverted article, this may be removed by 

 bisulphide of carbon. Tims, heat alone effects the transmutation. It is identical in 

 composition with ordinary phosphorus, and may be reconverted into it without loss 

 of weight, and that merely by change of temperature. This substance remains un- 

 altered in the atmosphere, is insoluble in bisulphide of carbon, in alcohol, ether, and 

 naphtha. It requires a heat of 260 Cent, to restore it to the ordinary state, and it 

 is only at that heat that it begins to take fire in the open air. It is not luminous 

 in the dark at any ordinary temperature. "When perfectly dry, amorphous phos- 

 phorus is a scarlet or carmine powder, which becomes darker when heated. On the 

 large scale it is prepared in dark masses of a red or dark brown colour. The great 

 advantages of this singular condition of phosphorus are, that it does not appear to 

 affect those persons who are employed in the manufacture of lucifer-matches with the 

 loathsome disease which the use of the ordinary phosphorus produces. See LUCIFER- 

 MATCHES. 



PHOSPHORUS MATCHES. See LUCIFER-MATCHES. 



PHOSPHORUS PASTE, for the Destruction of Eats and Mice. The Prussian 

 Government issued an ordormance on April 27, 1843, directing the following com- 

 position to be substituted for arsenic, for destroying rats and mice; enjoining the 

 authorities of the different provinces to communicate, at the expiration of a year, 

 the results of the trials made with it, with the view of framing a law on this sub- 

 ject. 



The following is the formula for this paste : 



Take of phosphorus 8 parts, liquefy it in 180 parts of lukewarm water; pour the 

 whole into a mortar, add immediately 180 parts of rye-meal; when cold, mix in 180 

 parts of butter melted, and 125 parts of sugar. If the phosphorus is in a finely- 

 divided state, the ingredients may be all mixed at once without melting them. This 

 mixture will retain its efficacy for many years, for the phosphorus is preserved by the 

 butter, and only becomes oxidised on the surface. Rats and mice eat this mixture 

 with avidity ; after which they swell out, and soon die. Several similar preparations 

 are now made in this country for the destruction of vermin. 



PHOTO-GAIiVAWOGRAPHY. A name given to a process invented by 

 Mr. Pretsch, for producing engravings from photographs, by the application of the 

 galvano-plastic process. It is not now employed, although great efforts were made 

 to introduce it to the public. The principles involved are sufficiently described in 

 the article on PHOTOGRAPHIC ENGRAVING. 



PHOTOGE3XT. Syn. Paraffin Oil. A term which has recently found its way into 

 commerce, to designate certain oils or naphthas for illuminating purposes. It is gene- 

 rally prepared from shales, brown coals, or cannels. Boghead coal, and' the numerous 

 varieties of inflammable shales which more or less resemble it, are specially adapted 

 for the preparation of photogen. The chief physical difference between photogen and 

 ordinary coal-oils of the same boiling-point, is the specific gravity, with which the 

 former varies from 0'820 to 0'830, whereas common coal-naphtha never has a less 

 density than O'SoO. It is true that photogen maybe obtained of as high a density 

 as 0-900, but then it will be of an excessively high boiling-point, and, in all proba- 

 bility, saturated with paraffin. 



The light oil known as photogen may be obtained from common bituminous coals 

 by distilling them at a lower temperature than is employed in gas-works. To obtain 

 the maximum amount of photogen from coal, the temperature should not be much 

 above 700 Cent. 



Preparation. The coals, broken into small pieces (the smaller the better), are to be 



