CHEMISTRY. 
lary tube ; pour weak fulphuric acid in at the other neck. 
At the inftant the gas is difengaged,. prelent a lighted 
taper, the gas catches flame, and forms what is called 
the philofophic candle, which burns as long as there is 
any difengagement of gas. 
This experiment may be made in a different way. Fill 
a large bell-glafs, as fliewn at fig. 14, with hydrogen gas; 
at the neck put a flop-cock, luftaining a copper tube 
either ftrait or bent; comprefs the gas by putting the 
bell-glafs below the level of the water in the pneumatic 
ciflern; then turn the cock, and prelent a lighted taper 
to the extremity : the gas takes fire immediately. Or a 
bladder may be tied to a flop-cock, or, more Amply flill, 
to a fmall giafs tube; drive out the gas by preflure, and 
the effect will be the fame. From thefe experiments it 
appears, that hydrogen gas, which is not inflammable 
of itfelf, only enjoys this property when in contact with 
atmofpherical air. 
Hydrogen gas, mixed with atmospherical 
air.- —Fill a bottle with atmofpherical air and hydrogen 
gas, fo that the atmofpherical air forms about two-thirds 
of the mixture; and apply a lighted taper. The flame 
is not then feen to defcend by degrees into the bottle: 
the inflammation is fudden, and accompanied with real 
explofion or detonation. 
Hydrogen gas and oxygen gas.- —Pafs under an 
inverted jar two-thirds of hydrogen gas, and one-third 
of oxygen gas; apply a light to the mixture; the in¬ 
flammation is total and initanianeous, and the detona¬ 
tion very loud. The mixture of thefe two gafes is called 
thundering air. If hydrogen gas alone be blown through 
a bladder into foap-liids, and a lighted taper be brought 
in contaft with the bubbles thereby railed, the com- 
buftion is fucceflive and without noile ; but, if the fame 
experiment be made with a mixture of hydrogen gas 
and oxygen gas, there will be a ftrong explofion. The 
loudnefs of the detonation arifes only from the due pro¬ 
portion of the mixture, which is totally burnt.. Hydro¬ 
gen gas is improper for relpiration. Take a bell-glafs 
and fill it with hydrogen gas, pat in a bird or other ani¬ 
mal, and coverit over to preventthe fluid from efcaping: 
The animal is immediately feized with violent convul- 
fions', and foon dies. 
Of CARBON. 
Carbon, or coal, the bafis of animal and vegetable 
fubftances, is prefent alrnoft eveiy where. Five fpecies 
may be diftinguifhed: vegetable, animal, and foflile, coal; 
wood charred in the earth, wood charred in water. The 
two firft fpecies arife from the diflillation of animal and 
vegetable fubftances: but pure carbon is not produced 
this way ; it is previoufly neceflary, by proper walkings 
in clear water, to extract all the lalts which are mixed 
and confounded therewith; then the carbon is to be 
dried with a violent heat in clofed veffels; this is a ne- 
ceflary precaution, for the laft drops of water adhere fo 
ftrongly as to be decompofed, and furnilh hydrogen gas 
and carbonic acid. 
Carbonic acid produces alfo, by decompofition, very 
pure carbon. Put into a giafs tube, clofed at one end, 
one part of phofphorus, and over that five parts of cal¬ 
careous carbonat in line powder; let the tube end in a 
point by means of a capillary point; place the tube in 
the middle of a furnace, fo that the fuel can only heat 
the carbonate, the end of the tube containing the phof¬ 
phorus being then in the alh-hole, as reprefented in the 
plate, at fig. 15; fallen the tube with a wire, and heat 
it; when the fait is very hot, raife the tube that the phof¬ 
phorus may burn. At this temperature the phofphorus 
feizes on the oxygen of the carbonic acid, and becomes 
phofphoric acid, which unites with lime to form a cal¬ 
careous phofphat, while the carbon is left to itfelf. By 
walhing the relult of this operation in water, the carbon 
is feparated. 
Expofed to the air, carbon burns, reddens, and gives 
*99 
out light, but no flame. If the experiment be made un¬ 
der a bell-glafs filled with atmofpherical air, the com- 
buftion of the carbon abforbs only about fifteen parts of 
the oxygen, becaufe the azot which is difengaged, fur- 
rounds the charcoal, and leflens the combullion. II char¬ 
coal be burnt under a bell-glafs, or in ajar filled with 
pure oxygen gas, the combullion is complete; the car¬ 
bon takes up all the oxygen, and makes a frelh com¬ 
bination : this is called carbonic acid. If water be palled 
under the giafs, and it be put in motion, the gas is dif- 
folved in the water, and the refult is liquid carbonic acid, 
which is known by its properties. 
Charcoal is very greedy of air. If a piece of charcoal, 
well dried, be put under a jar, in a mercurial bath, filled 
with that metal, the charcoal will be leen to abforb the 
air, and the mercury to rife pretty quick ; but, if aque¬ 
ous gas be palled under the jar, then the charcoal ab¬ 
forbs the humidity in preference : it takes the water and 
leaves the air, and the mercury finks again. 
Carbon melts in hydrogen gas: if carbonated hydro¬ 
gen gas be burnt with oxygen, water and carbonic acid 
are the produdls. The hydrogen gas, which has dif- 
folved carbon, acquires a greater fpecific gravity. Car¬ 
bonated hydrogen gas is difengaged in general in all 
diftillations of vegetable and animal fubftances; for the 
hydrogen exifts in a folid. ftate in plants, and goes off 
in gas only by means of the caloric communicated to it 
by the fire employed in the diflillation; and it diftblves 
charcoal. 
Of PHOSPHORUS. 
Phofphorus was originally obtained from urine. Ac¬ 
cording to Leibnitz, the diicovery of phofphorus is due 
to an alchemift named Brandt, a citizen of Hamburg, 
who difeovered it in 1667. Kunckel afl'oeiated with a 
certain perfon named Kraft't, to purchafe this fecret; but 
the latter having purchafed it, and refufing to commu¬ 
nicate it to Kunckel, he refolved to make a l'eries of 
experiments on urine, from which he knew it was ex¬ 
tracted, in order to difeover it. His inquiries were at¬ 
tended with fuccefs, and therefore he ought to be re¬ 
garded as the true inventor. Some perfons likewile at¬ 
tribute the honour of this difeovery to Boyle, who in 
faff depofited a fmall quantity, in the year 1680, in the 
hands of the fecretary of the royal fociety of London ; 
but Stahl affirms that Kraft't told him that he communi¬ 
cated the procefs of making phofphorus to Boyle ; Boyle 
communicated his procels to a German, named Godfreid 
Hanckwitz, who had a good laboratory at London, and 
was for a long time the only perfon who made phofphorus, 
and fold it to all the philofophers throughout Europe. Not- 
withftanding a great number of receipts for making phof¬ 
phorus, and among others thofe of Boyle, Kraft't, Brandt, 
Hoffman,Teichmeyer, Frederic Hoffman, Neiwentyt.and 
Wadelius, have been publillied, fince the year j68o, to 
the commencement of the prefent century, no chemift fuc- 
ceeded in preparing it; and the procels was in reality a 
fecret, till a ftranger, in 1737, offered at Paris to com¬ 
municate a fuccefsful method of making it. The aca¬ 
demy nominated four chemifts, Hellot, Dufay, Geoffroy, 
and Duhamel, to attend this operation in the laboratory 
cf the royal garden. The procefs fucceeded very well, 
the. minifter rewarded the foreigner, and M. Hellot de- 
feribed it very accurately, in a memoir inferted among 
thofe of the academy for the year 1737- The operation 
confifts in evaporating five or fix hoglheads of urine, till 
it is reduced into a granulated, hard, black, and Ihining, 
fubftance; this refidue is calcined in an iron-pot, whole 
bottom is heated red-hot, till no more fumes arile, and 
a fmell like that of peach-bloffoms is perceived ; the cal¬ 
cined matter is lixiviated with about twice its weight of 
hot water, and is dried after the waterhas been decantedofF. 
Three, pounds of this matter are then mixed with One 
pound and a half of coarfe land, or pounded flone-ware, 
and four or five ounces of the powder of charcoal of 
beechj. 
