PHO

PH O

( 210 )

tlie phofphorus partly concretes within the tubeand partly falls to the bottom of the water.

The proportion of one part of charcoal to two(by weight) of the concrete acid, is much morethan is neceflary to decompofe the acid, butit is ufeful to have an excefs of charcoal toprotect the retort from being corroded by theacid, which operates as a powerful flux for allearthy mixtures.

The retort being filled with the mixture ofcharcoal and acid, (which may be done nearlyto the neck in cafe the acid be thoroughly driedprevioufly in a low red heat) put it into thefurnace and raife the heat very gradually to amoderate rednefs. At firft with the air of theveflels a quantity of mixed gaffes,, chiefly car-bonic acid and hydrocarbonate, pafs over, andwhen thefe have nearly ceafed, increafe theheat to a full glowing white-red and keep it upto this degree during the remainder of thediflillation. The firft indication of the pro-duction of phofphorus is that the gas as itpaffes out of the water becomes white andluminous in the dufk, which is followed by agas ftill more inflammable, each bubble ofwhich takes fire in the air and burns with abrilliant flame and flight fnapping noife as foonas it rifes above the furface of the waterbeneath which the end of die tube is dipped.After this the phofphorus rifes in fubftance,and if the quantity of materials in the retort belarge, fome of it falls down in drops into thepan of water, where it immediately congeals,but by far the greater part concretes in thatpart of the neck of the retort which reaches outof the furnace, and in the tube by which it iselongated. Sometimes the paifage is entirelyblocked up by the congealed phofphorus whichmight endanger the burfting of the retort, toafeertain which a flexible wire may be thrift! upnow and then (but without raifmg the end ofthe tube out of the water) and if the paflage isnot free, lay a red hot iron bar on the outfideof the tube where the paflage of the wire isobftruCted, which will melt down the phof-phorus.

It is not eafy to afeertain when all thephofphoric aoid is decompofed, and all thephofphorus has palled over, for the efflux ofgas nearly ceafes before the diflillation is com-pieated, lb that experience muft guide theoperator when to ftop. If the retort continuesfound, no lofs of phofphmus is incurred bycontinuing the fire longer than neceflary, fothat it is better to exceed than to fall fhort ofthe requifite time. But as earthen veflels will

fooner or later vitrify and fink down in a veryftrong heat, the fire fhould be kept below thedegree at which earthen fire-veflels foften, andthe retort fhould be now and then examined.Sometimes the retort unfortunately cracks inthe middle of the diftillation, which may bedifeovered by a bright green flame and a denfewhite fmoke around the part that has givenway. This may fometimes be clofed by im-mediately prefling on the part fome linfeed oilfire lute, (as deferibed in the article Cement )but if this fails the retort muft be taken out,and as much of the materials as poifible favedfor a future operation.

When the diftillation is judged to be fmifhed,remove the tube from the water and inftantlycork it tightly to prevent the accefs of air,which would inflame the phofphorus, and letthe retort cool. When quite cold break it witha hammer juft where the neck joins with thebody of the veil'd, holding it in the famepofition as it flood in the furnace, to preventthe charcoal within the retort from mixing withthe phofphorus fublimed in the neck and tube,and throw the latter into cold water. Thephofphorus may then be got out by removingthe tube into boiling water, which melts outthe phofphorus, but in this as in all operationson this inflammable material whenever a fuffi-cient heat to melt it is applied, (which, is aboutioo°) every thing fhould be done under water,as it kindles a little above its melting tempera-ture, and burns vehemently the" moment itbecomes expofed to the air.

'The phofphorus produced in this procefs isvery brown and foul, and is mixed with a gooddeal of a brown red powder which dift'ufesitfelf in water like clay, and confifts chieflyof phofphorus fo far oxygenated as to be nolonger combuftible.

The quantity of prodmSl varies extremely,but is the moft when the materials are dry andthe diftillation flow. Pelletier obtained 60 oz.of phofphorus by a Angle procefs from theacid of 36 lbs. (576 oz.) of bone-afh decom-pofed by 30 lbs. of fulphuric acid.

The brown red phofphorus may be purifiedby feveral methods. The fimpleft is tJ lefollowing: take a piece of thin white leather,put the impure phofphorus in the middle andtie up the ends very tight fo as to enclofe it ina leather bag; then plunge it into boiling waterand fqueeze the bag with the fingers, by whichthe melted phofphorus will ooze through indrops, that coalclce at the bottom of the waterinto a clear pure waxy phofphorus almoft tranf-