PH O

PH O

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philofophical curiofity, for making luminouswriting and other entertainment.

In this proeefs the quantity of phofphorusyielded was exceffively fmall compared to thatof the urine employed, for of all the con-ftituents of urine it is only the phofphat ofammonia that is concerned in the production ofphofphotus, the heat driving off the ammonia,the phofphoric acid is left without a bafe, andit is then decompofed by the charcoal whichabftradts its oxygen, and leaves the phofphorusuncombined and volatilizable by the heat. Thephofphat of foda of the urine is not altered.

• After a while Margraaf, an excellent chemiftof Berlin 15 found that the product of phofphoruswas much augmented by adding to the extradfof urine fome of the plumbum corneum, or fub-muriat of lead, left after di Hilling fal ammoniacand litharge, the reafon of which is found tobe that this fait decompofes (in part at leaf!)the phofpha* of foda of the urine, whichhitherto had been ufelefs, forming a phofphatof lead, which is equally decompofable bycharcoal with the phofphat of ammonia.

This method has been Hill further improvedof late years by Giobert of Turin , whofe proeefsfor preparing phofphorus from urine we maymention here, though it is not the one generallyemployed. It is the following: into a quantityof urine pour a moderately dilute folution ofacetite or nitrat of lead, which will immediatelyproduce a copious greyifh white precipitate ofphofphat of lead, and add the metallic folutionas long as it produces any confiderable milki-nefs. Run the whole through a linen filter,and immediately mix the phofphat of lead thatremains with a fourth of its weight of finelypowdered charcoal, (the exa£t proportions ofeach being of no great confequence) and drythe black pafty mafs in an iron pot heatedbarely red. Then transfer it to an earthenretort, and raife the heat to moderate rednefs.Much fetid ammoniacal oily vapour pafles overat firft, and till this difappears the heat is notto be raifed higher than to a low reft. Thenchange the empty receiver for one half full ofwater, or dip the elongated beak of the receiverabout an inch under water, and encreale theheat to a full glowing red, and in about half anhour the phofphorus diftills. The particularmanagement oi the proeefs and fubfequentrefining of the phofphorus are the fame as areemployed in the more common proeefs, andwill be prefently deferibed. When all istinifhed, the retort will contain the lead re-

An. Chi

duced, and mixed with the undecompofedcharcoal, but as fome chemifts afTert, it is inthe ftate of phofphuret of lead. The averagequantity of phofphorus yielded is found to beabout 14 to 18 parts from 100 of the phofphatof lead well walhed and dried, but this is notneceflary, as the other urinous matters thatadhere to it are readily difperfed in the diftilla-tion. It does not appear to require fo intenfea heat to obtain phofphorus in this way as inthat which will be next deferibed. The faltsof zinc added to urine produce alfo a precipitatewhich is the phofphat of zinc, and fome phof-phorus may be procured from it by diftillation,but much lefs than from the phofphat of lead :as the zinc rifes in diftillation along with thephofphorus, and phofphuret of zinc concretesin the neck of the retort.

Whilft phofphorus was prepared in the oldway by evaporating urine, it was a very difguft-ing, tedious, and fomewhat difficult proeefs,but it was foon difcover.ed (by Gahn, as iscommonly faid, but as appears from fomeauthority, more probably by Scheele) that thephofplioric acid was contained in abundance inthe white earth left after the calcination ofBones, united with lime, and when feparatedby chemical means phofphorus could be pre-pared from it with much more eafe andcertainty. This method is now almoft uni-verfally preferred, as it requires but little ap-paratus, and is in no way offenfive nor difficult.The earth of bones confifts of phofphat of lime,(mixed with a little carbonat) and as the ful-phuric acid has a ftronger affinity for lime thanthe phofphoric, it is this which is employed forprocuring the phofphoric. This proeefs ofmaking phofphorus confifts of two diftinftoperations, viz. the feparation of the phofphoricacid from the bone-afh, and the diftillation ofthe acid and charcoal to obtain the phofphorus:it is performed in the following manner, withfome flight variations. Take any quantity(fuppofe 4 lbs.,) of powdered bone-afh, or cal-cined earth of bones, fuch as cupels are madeof, put it into an earthen pan capable ofholding 4 gallons, mix it at firft with about 4quarts of water, and then add gradually withinceffimt ftirring, 2 lbs. of ftrong fulphuricacid. A very great heat is excited by themixture, and fome effervefcence, (which laftarifes from the carbonat of lime,) and it fhouldbe prevented from clotting by rapid ftirring.ft hen add about a gallon of water and allow itto remain for a day with occafional ftirring.

1, Tom xii.