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An Introduction to Chemical Science

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Water glass, sodium or potassium silicate, used somewhat for
making artificial stone, is made by fusing SiO2 with Na2CO3 or
K2CO3, and dissolving in water. Silicic acid forms the basis of a
very important series of compounds, - the silicates. The above
two are the only soluble ones, and may be called liquid glass.

Chapter XLII.

GLASS AND POTTERY.

Examine white sand, calcium carbonate, sodium carbonate, smalt;
bottle, window, Bohemian and flint glass.

218. Glass is an Artificial Silicate.--Si02 alone is almost
infusible, as is also Ca0; but mixed and heated the two readily
fuse, forming calcium silicate. Ca0 + SiO2 = ? Notice that Si02
is the basis of an acid, while CaO is essentially a base, and the
union of the two forms a salt. There are four principal kinds of
glass: (1) Bohemian, a silicate of K and Ca, not easily fused,
and hence used for chemical apparatus where high temperatures are
required; (2) window or plate glass, a silicate of Na and Ca; (3)
bottle glass, a silicate of Na, Ca, Al, Fe, etc., a variety which
is impure, and is tinged green by salts of Fe; (4) flint glass, a
silicate of K and Pb, used for lenses in optical instruments, cut
glass ware, and, with B added, for paste, or imitation diamonds,
etc. Pb gives to glass high refracting power, which is a valuable
property of diamonds, as well as of lenses.

219. Manufacture.--Pure white sand, Si02, is mixed with CaCO3 and
Na2CO3, some old glass - cullet - is added, and the mixture is
fused in fire-clay crucibles. For flint glass, Pb304, red lead,
is employed. If color is desired, mineral coloring matter is also
added, but not always at this stage. CoO, or smalt, gives blue;
uranium oxide, green; a mixture of Au and Sn of uncertain
composition, called the "purple of Cassius," gives purple. MnO2
is used to correct the green tint caused by FeO, which it is
supposed to oxidize. Opacity, or enamel, as in lamp-shades, is
produced by adding As2O3, Sb2O3, SnO2, cryolite, etc. The glass-
worker dips his blowpipe--a hollow iron rod five or six feet
long--into the fused mass of glass, removes a small portion,
rolls it on a smooth surface, swings it round in the air, blowing
meanwhile through the rod, and thus fashions it as desired, into
bottles, flasks, etc. For some wares, e.g. common goblets, the
glass is run into molds and stamped; for others it is blown and
welded. All glass must be annealed, i.e. cooled slowly, for
several days. The molecules thus arrange themselves naturally. If
not annealed, it breaks very easily. It may be greatly toughened
by dipping, when nearly red-hot, into hot oil. Cut glass is
prepared at great expense by subsequent grinding. Glass may be
rendered semi-opaque by etching either with HF, or with a blast
of sand.

220. Importance.--Few manufactured articles have more importance
than glass. Without it the sciences of chemistry, physics,
astronomy, microscopic anatomy, zoology, and botany, not to
mention its domestic uses, would be almost impossible.

221. Porcelain and Pottery.--Genuine porcelain and china-ware are
made of a fine clay, kaolin, which results from the
disintegration of feldspathic rocks. Bricks are baked clay. The
FeO in common clay is oxidized to Fe2O3, on heating, a process
which gives their red color. Some clay, having no Fe, is white;
this is used for fire-bricks and clay pipes. That containing Fe
is too fusible for fire-clay, which must also have much SiO2. The
electric arc, however, will melt even this, and the most
refractory vessels are of calcium oxide or of graphite. Pottery
is clay, molded, baked, and either glazed, like crockery, or
unglazed, like flower-pots. Jugs and coarse earthenware are
glazed by volatilizing NaCl in an oven which holds the porous
material. This coats the ware with sodium silicate. To glaze
china, it is dipped into a powder of feldspar and SiO2 suspended
in water and vinegar, and then fused. If the ware and glaze
expand uniformly with heat, the latter does not crack.

Chapter XLIII.

METALS AND THEIR ALLOYS.

222. Comparison of Metals and Non-Metals.--The majority of
elements are metals, only about a dozen being non-metallic in
their properties. The division line between the two classes is
not very well defined; e.g. As has certain properties which ally
it to metals; it has other properties which are non-metallic. H
occupies a place between the two classes. The following are the
more marked characteristics of each group: -

METALS.

1. Metals are solid at ordinary temperatures, and usually of high
specific gravity.

Exceptions: Hg is liquid above -39.5 degees; Li is the lightest
solid known; Na and K will float on water.

2. Metals reflect light in a way peculiar to themselves. They
have what is called a metallic luster.

3. They are white or gray. Exceptions: Au, Ca, Sr are yellow; Cu
is red.

4. In general they conduct heat and electricity well.

NON-METALS. 1. Non-metals are either gaseous or solid at ordinary
temperatures, and of low specific gravity. Exceptions: Br is a
liquid; I has the heaviest known vapor.

2. Non-metallic solids have different lusters, as glassy,
resinous- silky, etc. Exceptions: I, B, and C have metallic
luster.

3. Non-metals have no characteristic color.

4. They are non-conductors of heat and electricity. Exceptions: C
and some others are conductors. 5. They are usually malleable and
ductile.

6. They form alloys, or "chemical mixtures," with one another,
similar to other solutions. Exceptions: Some, as Ph and Zn, will
not alloy with one another.

7. Metals are electro-positive elements, and unite with O and H
to form bases. Exceptions: Some of the less electro-positive
metals, with a large quantity of O, form acids, as Cr, As, etc.

Numbers 2, 6, and 7 are the most characteristic and important
properties.

5. They are deficient in malleability and ductility.

6. They often form liquid solutions, similar to alloys in metals.

7. Non-metals are electronegative, and with H, or with H and O,
form acids.

Examine brass, bronze, bell-metal, pewter, German silver, solder,
type-metal.

223. Alloys.-An alloy is not usually a definite chemical
compound, but rather a mixture of two or more metals which are
melted together. One metal may be said to dissolve in the other,
as sugar dissolves in water. The alloy has, however, different
properties from those of its elements. For example, plumber's
solder melts at a lower temperature than either Ph or Sn, of
which it is composed. Some metals can alloy in any proportions.
Solder may have two parts of Sn to one of Pb, two of Pb to one of
Sn, or equal parts of each, or the two elements may alloy in
other proportions. Not all metals can be thus fused together
indefinitely; e.g., Zn and Pb. Nickel and silver coins are
alloyed with Cu, gold coins with Cu and Ag.

Gun-metal, bell-metal, and speculum-metal are each alloys of Cu
and Sn. Speculum-metal, used for reflectors in telescopes, has
relatively more Sn than either of the others; gun-metal has the
least. An alloy of Sb and Pb is employed for type-metal as it
expands at the instant of solidification. Pewter is composed of
Sn and Pb; brass, of Cu and Zn; German silver, of brass and Ni;
bronze, of Cu, Sn, and Zn; aluminium bronze, of Cu and Al.

224. Low Fusibility is a feature of many alloys. Wood's metal,
composed of Pb eight parts, Bi fifteen, Sn four, Cd three, melts
at just above 60 degrees, or far below the boiling-point of
water. By varying the proportions, different fusing-points are
obtained. This principle is applied in automatic fire alarms, and
in safety plugs for boilers and fire extinguishers. Water pipes
extend along the ceiling of a building and are fitted with plugs
of some fusible alloy, at short distances apart. When, in case of
fire, the heat becomes sufficiently intense, these plugs melt and
the water flows out.

225. Amalgams.--An amalgam is an alloy of Hg and another metal.
Mirrors are "silvered" with an amalgam of Sn. Tin-foil is spread
on a smooth surface and covered with Hg, and the glass is pressed
thereon.

Various amalgams are employed for filling teeth, a common one
being composed of Hg, Ag, and Sn. Au or Ag, with Hg, forms an
amalgam used for plating. Articles of gold and silver should
never be brought in contact with Hg. If a thin amalgam cover the
surface of a gold ring or coin, Hg can be removed with HNO3, as
Au is not attacked by it. Would this acid do in case of silver
amalgam? Heat will also quickly cause Hg to evaporate from Au.

CHAPTER XLIV.

SODIUM AND ITS COMPOUNDS.

Examine NaCl, Na2SO4, Na2CO3, Na, NaOH, HNaCO3, NaNO3.

226. Order of Derivation.--Though K is more metallic, or electro-
positive, than Na, the compounds of Na are more important, and
will be considered first. The only two compounds of Na which
occur extensively in nature are NaCl and NaNO3. Almost all others
are obtained from NaCl, as shown by this table, which should be
memorized and frequently recalled.


) Na
NaCl ) Na2SO4) Na2CO3) NaOH
NaNO3) ) ) HNaCO3



From what is Na2SO4 prepared, as shown by the table? Na2CO3? Na?

227. Occurrence and Preparation of NaCl.--NaCl occurs in sea
water, of which it constitutes about three per cent, in salt
lakes, whose waters sometimes hold thirty per cent, or are nearly
saturated, and, as rock salt, in large masses underground. Poland
has a salt area of 10,000 square miles, in some parts of which
the pure transparent rock salt is a quarter of a mile thick. In
Spain there is a mountain of salt five hundred feet high and
three miles in circumference. France obtains much salt from sea
water. At high tide it flows into shallow basins, from which the
sun evaporates the water, leaving NaCl to crystallize. In Norway
it is separated by freezing water, and in Poland it is mined like
coal. In New York and Michigan it is obtained by evaporating the
brine of salt wells, either by air and the sun's heat, or by
fire. Slow evaporation gives large crystals; rapid, small ones.

228. Uses.--The main uses are for domestic purposes and for
making the Na and Cl compounds. In the United States the
consumption amounts to more than forty pounds per year for every
person.

229. Sodium Sulphate.--What acid and what base are represented by
Na2SO4? Which is the stronger acid, HCl or H2SO4? Would the
latter be apt to act on NaCl? Why?

230. Manufacture.--This comprises two stages shown by the
following reactions, in which the first needs moderate heat only;
the last, much greater.

(1) 2 NaCl + H2SO4 = HNaSO4 + NaCl + HCl:
(2) NaCl + HNaSO4 = Na2S4 + HCl.

The operation is carried on in large furnaces. The gaseous HCl is
passed into towers containing falling water in a fine spray, for
which it has great affinity. The solution is drawn off at the
base of the tower. Thus all commercial HCl is made as a by-
product in manufacturing Na2SO4.

When crystalline, sodium sulphate has ten molecules of water of
crystallization (Na2SO4, 10 H2O); it is then known as Glauber's
salt. This salt readily effloresces; i.e. loses its water of
crystallization, and is reduced to a powder. Compute the
percentage of water.

231. Uses.--The leading use of Na2SO4 is to make Na2CO3; it is
also used to some extent in medicine, and in glass manufacture.
232. Sodium Carbonate.--Note the base and the acid which this
salt represents. Test a solution of the salt with red and blue
litmus, and notice the alkaline reaction. Do you see any reason
for this reaction in the strong base and the weak acid
represented by the salt?

233. Manufacture.--Na2CO3 is not made by the union of an acid and
a base, nor is H2CO3 strong enough to act on many salts. The
process must be indirect. This consists in reducing Na2SO, to
Na2S, by taking away the O with C, charcoal, and then changing
Na2S to Na2O3 by CaCO3, limestone. The three substances, Na2SO4,
C, CaCO3, are mixed together and strongly heated. The reactions
should be carefully studied, as the process is one of much
importance.

(1) Na2SO4 + 4 C = Na2S + 4 CO.
(2) Na2S + CaCO3 = CaS + Na2CO3.

Observe that C is the reducing agent. The gas CO escapes. The
solid products Na2CO3 and CaS form black ash, the former being
very soluble, the latter only sparingly soluble in water. Na2CO3
is dissolved out by water, and the water is evaporated. This
gives commercial soda. CaS, the waste compound in the process,
contains the S originally in the H2SO4 used. This can be
partially separated and again made into acid. Describe the
manufacture of NaCO3 in full, starting with NaCl. This is called
the Le Blanc process, but is not the only one now employed to
produce this important article.

234. Occurrence.-Sodium carbonate is found native in small
quantities. It forms the chief surface deposit of the "alkali
belt" in western United States, where it often forms
incrustations from an inch to a foot in thickness. It was
formerly obtained from sea-weeds, by leaching their ashes, as, by
a like process, K2CO3 was obtained from land plants.

235. Uses.--Na2CO3 forms the basis of many alkalies, as H2SO4
does of acids. Of all chemical compounds it is one of the most
important, and its manufacture constitutes one of the greatest
chemical industries. Its economical manufacture largely depends
on the demand for HCl, which is always formed as a by-product. As
but little HCl is used in this country, Na2CO3 is mostly
manufactured in Europe. The chief uses are for glass and
alkalies.

236. Sodium.--Na must always be kept under naphtha, or some other
liquid compound containing no O, since it oxidizes at once on
exposure to the air. For this reason it never occurs in a free
state.

237. Preparation.-By depriving Na2CO3 of C and O, metallic sodium
is formed. As usual, heated charcoal is the reducing agent. The
end of the retort, which holds the mixture, dips under naphtha.

Na2CO3 + 2 C = 2 Na + 3 CO. The process is a difficult one, and
Na brings five dollars per pound, though in its compounds it is a
third as common as Fe. K is as abundant as Na, but more difficult
of separation, and is worth three dollars per ounce. Notice the
position of K and Na at the positive end of the elements.

238. Uses.--Na is used to reduce Al, Ca, Mg, Si, which are the
most difficult elements to separate from their compounds. It acts
in these cases as a reducing agent.

239. Sodium Hydrate. Review Experiment 62.

Experiment 118.--Put into a t.t. 10cc. H2O and 2 or 3 g. NaOH.
Note its easy solubility. Test with litmus. Will it neutralize
any acids?

240. Preparation. -- Sodium hydrate, caustic soda, or soda by
lime, is made by treating a solution of Na2CO3 with milk of lime.
CaCO3 is precipitated and al- lowed to settle, the solution is
poured off, and NaOH is obtained by evaporating the water and
running the residue into molds.

241. Use.--NaOH is a powerful caustic, but its chief use is in
making hard soap.

242. Hydrogen Sodium Carbonate.--Hydrogen so- dium carbonate,
bicarbonate of sodium, acid sodium carbonate, cooking-soda, etc.,
HNaCO3, is prepared by passing CO2 into a solution of Na2CO3.
Na2CO3 + H2O + CO2 = 2 HNaCO3. Test a solution of it with litmus.
Account for the result. Its use in bread-making depends on the
ease with which CO2 is liberated. Even a weak acid, as the lactic
acid of sour milk, sets this free, and thus causes the dough to
rise.

243. Sodium Nitrate.--Sodium nitrate occurs in Chili and Peru. It
is the main source of HNO3.

Review Experiments 46 and 52. From NaNO3 is also made KNO3,
(NaNO3 + KCl = NaCl + KNO3), one of the ingredients of gunpowder.
By reason of its deliqcescence NaNO3 is not suitable for making
gunpowder, though it is sometimes used for blasting-powder. The
action of the latter is slower than that made from KNO3. NaNO3 is
cheaper and more abundant than KNO3; this is true of most Na
compounds in comparison with those of K.

Chapter XLV.

POTASSIUM AND AMMONIUM.

POTASSIUM AND ITS COMPOUNDS.

Examine K, KCl, K2SO4, K2CO3, KOH, HKCO3, KCLO3, KCN.

244. Occurrence and Preparation.--Potassium occurs only in
combination, chiefly as silicates, in such minerals as feldspar
and mica. By their disintegration it forms a part of soils from
which such portions as are soluble are taken up by plants. The
ashes of land-plants are leached in pots to dissolve K2CO3; hence
it is called potash. Sea-plants likewise give rise to Na2CO3.
Wood ashes originally formed the main source of K2CO3. From
plants this substance is taken into the animal system, and makes
a portion of its tissue. Sheep excrete it in sweat, which is then
absorbed by their wool. Large quantities are now obtained by
washing wool and evaporating the water. K2CO3 and other compounds
of K are mainly derived from KCl, beds of which exist in Germany.

In the following list each K compound is prepared like the same
Na compound, and the uses of each of the former are similar to
those of the latter. K compounds are made in much smaller
quantities than those of Na, as KCl is far less common than NaCl.


{ K
KCl { K2SO4 { K2CO3 { KOH
KNO3 { { HKCO3



Examine specimens of each, side by side with like Na compounds.
Describe in full their preparation, giving the reactions. Also,
perform theexperiments given under Na, substituting K therefor.
From KOH are made KClO3 and KCN.

KOH {KCl03
{KCN


245. Potassium Chlorate.--KCl03 is made by passing Cl into a hot
concentrated solution of KOH.

6 KOH + 6 Cl = KCl03 + 5 KCl + 3 H2O

Its uses are making O, and as an oxidizing agent.

246. Potassium Cyanide, KCN, is a salt from HCN--hydrocyanic or
prussic acid. Each is about equally poisonous, and more so than
any other known substance. A drop of pure HCN on the tongue will
produce death quickly by absorption into the system. In examining
these compounds take care not to handle them or to inhale the
fumes. KCN is used as a solvent for metals in electro-plating,
and is the source of many cyanides, i.e. compounds of CN and a
metal. KCN is employed to kill insects for cabinet specimens. In
a wide-mouthed bottle is placed a little KCN, which is covered
with cotton, and over this a perforated paper. The bottle is
inverted over the insect, and the fumes destroy life without
injuring the delicate parts. HCN is made from KCN and H2SO4.

247. Gunpowder.--Gunpowder is a mixture of KNO3, C, and S. Heat
or concussion causes a chemical change, and transforms the solids
into gases. These gases at the moment of explosion occupy 1500 or
more times the volume of the solids. Hence the great rending
power of powder. If not confined, powder burns quietly but
quickly. The appended reaction is a part of what takes place, but
it by no means represents all the chemical changes.

2KNO3 + S + 3C =K2S + 2N + 3CO2.

From this equation compute the percentage, by weight, of each
substance used to make gunpowder economically.

Thoroughly burned charcoal, distilled sulphur, and the purest
nitre are powdered and mixed in a revolving drum,made into a
paste with water, put under great pressure between sheets of gun
metal, granulated, sifted, to separate the coarse and fine
grains, and glazed by revolving in a barrel which sometimes
contains a little powdered graphite.

Experiment 119.--Pulverize and mix intimately 4 g. KNO3, l/2 g.
S, 1/2 g. charcoal. Pile the mixture on a brick, and apply a
lighted match. The adhering product can be removed by soaking in
water.

AMMONIUM COMPOUNDS.

248. Read the chapter on NH3. Also, review the experiments on
bases. Examine NH4Cl, NH4NO3, (NH4)2SO4, (NH4)2CO3.

Ammonium, NH4, is too unstable to exist alone, but it forms salts
similar to those of K and Na. NH3 dissolved in water forms NH4OH.

The food of plants, as well as that of animals, must contain N.
It has not yet been shown that they can make use of that
contained in the air, but they do absorb its compounds from the
soil. All fertilizers and manures contain a soluble compound of
NH4. All NH4 compounds are now obtained either from coal, in
making illuminating-gas, or from bones, by distillation.

Suppose the product obtained from the gas-house to be NH4OH, how
would NH4Cl be made? (NH4)2SO4? NH4NO3? Write the reactions.
(NH4)2CO3 is made by heating NH4Cl with CaCO3. Give the reaction.

Chapter XLVI.

CALCIUM COMPOUNDS.

Examine CaCO3--marble, limestone, chalk, not crayon,--CaSO4 --
gypsum or selenite--CaCl2, CaO.

249. Occurrence.--The above are the chief compounds of Ca. The
element itself is not found uncombined, is very difficult to
reduce (page 141), is a yellow metal, and has no use. Its most
abundant compound is CaCO3. Shells of oysters, clams, snails,
etc., are mainly CaCO3, and coral reefs, sometimes extending
thousands of miles in the ocean, are the same. CaCO3 dissolves in
water holding CO2, and thence these marine animals obtain it and
therefrom secrete their bony framework. All mountains were first
laid down on the sea bottom layer by layer, and afterwards lifted
up by pressure. Rocks and mountains of CaCO3 were formed by
marine animals, and all large masses of CaCO3 are thought to have
been at one time the framework of animals. Marble is
crystallized, transformed limestone. The process, called
metamorphism, took place in the depths of the earth, where the
heat is greater than at the surface.

250. Lime.--If CaCO3 be roasted with C, CO2 escapes and CaO is
left. CaCO3 - CO2 = ? This is called burning lime, and is a large
industry in limestone countries. CaO is unslaked lime, quicklime
or calcium oxide. It may be slaked either by exposure to the
air, air-slaking, when it gradually takes up H2O and CO2; or by
mixing with H2O, water-slaking. Ca0 + H2O = Ca(OH)2.

Great heat is generated in the latter case, though not so much as
in the formation of KOH and NaOH. Like them, Ca(OH)2 dissolves in
water, forming lime-water. Milk of lime, cream of lime, etc.,
consist of particles of Ca(OH)2 suspended in H2O.

251. Uses of Lime--CaO is infusible at the highest temperatures.
If it be introduced into the oxy-hydrogen blow-pipe (page 28), a
brilliant light, second only to the electric, is produced. Mortar
is made by mixing CaO, H2O, and Si02. It hardens by evaporating
the extra H2O, absorbing CO2 from the air, and uniting with Si02
to form calcium silicate. It often continues to absorb CO2 for
hundreds or thousands of years before being saturated, as is
found in the Egyptian pyramids. Hence the tenacity of old mortar.
Hydraulic mortar contains silicates of Al and Ca, and is not
affected by water. What are the uses of mortar? Being the
important constituent of mortar and plaster, lime is the most
useful of the bases.

252. Hard Water.--Review Experiment 76. The solubility of CaCO3
in water that contains CO2 leads to important results. Much
dissolves in the waters of all limestone countries; and the
water, though perfectly transparent, is hard; i.e. soap has
little action on it. See page 187. Such water may be softened by
boiling, a deposit of CaCO3 being formed as a crust on the
kettle. Such water is called water of temporary hardness. MgCO3
produces a similar effect, and water containing it is softened in
the same way. Permanently hard waters contain the sulphates of Ca
and Mg, which cannot be removed by boiling, but may be by adding
(NH4)2CO3. 253. The Formation of Caves in limestone rocks is due
also to the solubility of CaCO3. Water collects on the mountains
and trickles down through crevices, dissolving, if it contains
CO2, some of the CaCO3, and thus making a wider opening, and
forcing its way along fissures and lines of least resistance into
the interior of the earth, or out at the base of the mountain.
Its channel widens as it dissolves the rock, and the stream
enlarges until in the course of ages an immense cavern may be
formed, with labyrinths extending for miles, from the entrance of
which a river often issues. In the long ages which elapsed during
the slow formation of Mammoth Cave its denizens lost many of the
characters of their ancestors, and eyeless fish and also eyeless
insects now abound there.

254. Reverse Action.--Drops of water on the roofs of these
caverns lose their CO2, and deposit CaCO3. Thus long, pendant
masses of limestone, called stalactites, are slowly formed on the
roofs like icicles. From these, water charged with CaCO3 drops to
the bottom, loses CO2 and deposits CaCO3, which forms an upward-
growing mass, called stalagmite. In time it may meet the
stalactite and form a pillar. Notice that the same action which
formed the cave is filling it up; i.e. the solubility of CaCO3 in
water charged with CO2.

255. Famous Marbles.--The marble from Carrara, Italy, is most
esteemed on account of a pinkish tint given by a trace of oxide
of iron. The best of Grecian marble was from Paros, one of the
Cyclades. The isles of the Mediterranean are of limestone, or of
volcanic, origin, often of both. 256. Calcium Sulphate occurs in
two forms, (1) with water of crystallization--gypsum, CaSO4 + 2
H2O, --(2) without it--anhydrite, CaSO4. The former, on being
strongly heated, gives up its water, and is reduced to a powder--
plaster of Paris. This, on being mixed with water, again takes up
2 H2O, and hardens, or sets, without crystallizing. If once more
heated to expel water, it will not again absorb it. When plaster
of Paris sets, it expands slightly, and on this account is
admirable for taking casts.

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