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List Of Contents | Contents of An Introduction to Chemical Science
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separated from its earthy impurities in Sicily by piling it into
heaps, covering to prevent access of air, and igniting, when some
of the S burns, and the rest melts and is collected. After
removal from the island it is further purified by distilling in
retorts connected with large chambers where it sublimes on the
sides as flowers of sulphur (Fig. 43). This is melted and run
into molds, forming roll brimstone. S also occurs as a
constituent of animal and vegetable compounds, as in mustard,
hair, eggs, etc. The tarnishing of silver spoons by eggs is due
to the formation of silver sulphide, Ag2S. The yellow color of
eggs, however, is due to oils, not to S.

The main compounds of S are sulphides and sulphates. What acids
do they respectively represent? Metallic sulphides are as common
as oxides; e.g. FeS2, or pyrite, PbS, or galenite, ZnS, or
sphalerite, CuFeS2, or chalcopyrite, etc. The most abundant
sulphate is CaSO4, or gypsum. BaSO4, or barite, and Na2SO4, or
Glauber's salt, are others.

The only one of these compounds that is utilized for its S is
FeS2. In Europe this furnishes a great deal of the S for H2SO4. S
is obtained by roasting FeS2. 3 FeS2 = Fe3S4 + 2 S.

188. Uses. -The greatest use of S is in the manufacture of H2SO4.
A great deal is used in making gunpowder, matches, vulcanized
rubber, and the artificial sulphides, like HgS, H2S, CS2, etc.
The last is a very volatile, ill- smelling liquid, made by the
combination of two solids, S being passed over red-hot charcoal.
It dissolves S, P, rubber, gums, and many other substances
insoluble in H2O.

189. Sulphur Dioxide, SO2, has been made in many experiments. It
is a bleaching agent, a disinfectant, and a very active compound,
having great affinity for water, but it will not support
combustion. Like most disinfectants, it is very injurious to the
system. It is used to bleach silk and wool--animal substances--
and straw goods, which Cl would injure; but the color can be
restored, as the coloring molecule seems not to be broken up, but
to combine with SO2, which is again separated by reagents. Goods
bleached with SO2 often turn yellow after a time.

190. SO2 a Bleacher.

Experiment 107.-Test its bleaching power by burning S under a
receiver under which a wet rose or a green leaf is also placed.

Chapter XXXVIII.

HYDROGEN SULPHIDE.

Examine ferrous sulphide, natural and artificial.

191. Preparation.

Experiment 108.--Put a gram of ferrous sulphide (FeS) into a t.t.
fitted with a d.t., as in Figure 32. Add 10cc. H2O and 5cc.
H2SO4. H2S is formed. Write the equation, omitting H2O. What is
left in solution?

192. Tests.

Experiment 109.-(1) Take the odor of the escaping gas. (2) Pour
into a t.t. 5cc.solution AgNO3, and place the end of the d.t.
from a H2S generator into the solution and note the color of the
ppt. What is the ppt.? Write the equation. (3) Experiment in the
same way with Pb(NO3)2 solution. Write the equation. (4) Let some
H2S bubble into a t.t. of clean water. To see whether H2S is
soluble in H2O, put a few drops of the water on a silver coin.
Ag2S is formed. Describe, and write the equation. Do the same
with a copper coin. (5) Put a drop of lead acetate solution,
Pb(C2H3O2)2, on a piece of unglazed paper, and hold this before
the d.t. from which H2S is escap- ing. PbS is formed. Write the
equation. This is the characteristic test of H2S.

193. Combustion of H2S

Experiment 110.--Attach a philosopher's lamp tube to the H2S
generator, and, observing the same precautions as with H, light
the gas. What two products must be formed? State the reaction.
The color of the flame. Compute the molecular weight and the
vapor density of H2S. 194. Uses. -Hydrogen sulphide or
sulphuretted hydrogen, H2S, is employed chiefly as a reagent in
the chemical laboratory. It forms sulphides with many of the
metals, as shown in the last experiment. These are precipitated
from solution, and may be separated from other metals which are
not so precipitated, as was found in the case of HCl and NH4OH.
The subjoined experiment will illustrate this. Suppose we wished
to separate Pb from Ba, having salts of the two mixed together,
as Pb(NO3)2 and Ba(NO3)2.

195. H2S an Analyzer of Metals.

Experiment 111.--Pass Some H2S gas in to 5cc.solution Ba(NO3)2.
No ppt. is formed. Do the same with Pb(NO3)2 solution. A ppt.
appears. Now mix 5cc.of each of these solutions in a t.t. and
pass the gas from a H2S generator into the liquid. What is
precipitated, and what is unchanged? When fully saturated with
the gas, as indicated by the smell, filter. Which metal is on the
filter and which is in the filtrate? Other reagents, as Na2CO3
solution, would precipitate the latter.

196. Occurrence and Properties. -- H2S is an ill-smell- ing,
poisonous gas, formed in sewers, rotten eggs, and other decaying
albuminous matter. It is formed in the earth, probably from the
action of water on sulphides, and issues with water from sulphur
springs.

A characteristic property is the formation of metallic sulphides,
as above. A skipper one night anchored his newly painted vessel
near the Boston gas-house, where the refuse was deposited, with
its escaping H2S. In the morning, to his consternation, the craft
was found to be black. H2S had come in contact with the lead in
the white paint, forming black PbS. This gradually oxidized after
reaching the open sea, and the white color reappeared.

Chapter XXXIX.

PHOSPHORUS.

NOTE.--Phosphorus should be kept in water, and handled with
forceps, never with the fingers, except under water, as it is
liable to burn the flesh and produce ulcerating sores. Pieces not
larger than half a pea should be used, and every bit should
finally be burned.

197. Solution and Combustion. Experiment 112. -Put 1 or 2 pieces
of P into an evaporating- dish, and pour over them 5 or 10cc.CS2
carbon disulphide. This will be enough for a class. When
dissolved, dip pieces of unglazed paper into it, and hold these
in the air, looking for any combustion as they dry. The P is
finely divided in solution, which accounts for its more ready
combustion then. Notice that the paper is not destroyed. This is
an example of so-called "spontaneous combustion." The burning-
point of P, the combustible, in air, the supporter, is about 60
degrees.

198. Combustion under Water.

Experiment 113. -Put a piece of P in a t.t. which rests in a
receiver, add a few crystals KClO3 and 5cc. H2O. Now pour in
through a thistle-tube 1cc.or more of H2SO4. Look for any flame.
H2SO4 acts very strongly on KClO3. What is set free? From this
fact explain the combustion in water.

199. Occurrence.--P is very widely disseminated, but not
abundant, and is found only in compounds, the chief of which is
calcium phosphate Ca3(PO4)2. It occurs in granite and other
rocks, as the mineral apatite, in soils, in plants, particularly
in seeds and grains, and in the bones, brains, etc., of
vertebrates. From the human system it is excreted by the kidneys
as microcosmic salt, HNaNH4PO4; and when the brain is hard-
worked, more than usual is excreted. Hence brain-workers have
been said to "burn phosphorus."

200. Sources.--Rocks are the ultimate source of this element.
These, by the action of heat, rain, and frost, are disintegrated
and go to make soils. The rootlets of plants are sent through the
soil, and, among other things, soluble phosphates in the earth
are absorbed, circulated by the sap, and selected by the various
tissues. Animals feed on plants, and the phosphates are
circulated through the blood, and deposited in the osseous
tissue, or wherever needed.

Human bones contain nearly 60 per cent of Ca3(PO4)2; those of
some birds over 80 per cent.

The main sources of phosphates and P are the phosphate beds of
South Carolina, the apatite beds of Canada, and the bones of
animals.

201. Preparation of Phosphates and Phosphorus.--Bone ash,
obtained by burning or distilling bones, and grinding the
residue, is treated with H1SO4, and forms soluble H4Ca(PO4)2,
superphosphate of lime, and insoluble CaSO4.

Ca3(PO4)2 + 2 H2SO4 = H4Ca(PO04)2 + 2 CaSO4. This completes the
process for fertilizers. If P is desired, the above is filtered;
charcoal, a reducing agent, is added to the filtrate; the
substance is evaporated, then very strongly heated and distilled
in retorts, the necks of which dip under water. It is then
purified from any uncombined C by melting in hot water and
passing into molds in cold water.

The work is very dangerous and injurious, on account of the low
burning-point of P, and its poisonous properties. While its
compounds are necessary to human life, P itself destroys the
bones, particularly the jaw bones, of the workers in it.

Between 1,000 and 2,000 tons are made yearly, mostly for matches,
but almost all at two factories, one in England, and one in
France. 202. Properties.--P is a colorless, transparent solid,
when pure; the impure article is yellowish, translucent, and
waxy. It is insoluble in water, slightly soluble in alcohol and
ether, and it readily dissolves in CS2, oil of turpentine, etc.
Fumes, having a garlic odor, rise when it is exposed to the air,
and in the dark it is phosphorescent, emitting a greenish light.

203. Uses. -The uses of this element and its compounds are for
fertilizers, matches, vermin poisons, and chemical operations.

204. Matches.-The use of P for matches depends on its low
burning-point. Prepared wood is dipped into melted S, and the end
is then pressed against a stone slab having on it a paste of P,
KClO3, and glue. KNO3 is often used instead of KClO3. In either
case the object is to furnish O to burn P. Matches containing
KClO3 snap on being scratched, while those having KNO3 burn
quietly. The friction from scratching a match generates heat
enough to ignite the P, that enough to set the S on fire, and the
S enough to burn the wood. Give the reaction for each. Paraffine
is much used instead of S. Safety matches have no P, and must be
scratched on a surface of red P and Sb2S3, or on glass.

205. Red Phosphorus.-Two or three allotropic forms of P are

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