SAFE CHEMICAL EXPERIMENTS
TWENTIETH-CENTURY “BLACK ART”
AS we stand in the twentieth century and peer curiously down the
corridors of Time, we find at all periods a deep interest in chemical
phenomena.
From the age when wisdom devoted itself in vain to the discovery of an
elixir of life and a method of transmuting the base metals into gold, to
the present day, when scientists pursue their experiments with more
reasonable and far worthier hopes, chemistry appears never to have
suffered any dearth of devotees, despite the fact that in olden times
one had either to occupy a high position or be a man greatly daring if
the Black Art was to be followed without fear of molestation.
To-day matters are different, so that the junior chemist need only
anticipate interference from _materfamilias_--a truly excellent person,
who, however, invariably regards chemical concoctions with hostile
contempt.
The obstacles instanced in the previous paragraph being foreseen,
perhaps no better initiative can be taken than to conciliate the
household deities by the performance of some particular experiment which
has an obviously beneficial result. This might happily be the removal of
ink stains from white linen; and naturally, if no cloth happen to be so
disfigured, some arrangement must be made whereby the ink is
accidentally spilt!
EXPERIMENTS WITH CHLORINE
(1) _Apparatus._--Erect a 4-oz. round-bottom flask about 8 inches above
the table (A, Fig. 1), by clamping its neck in a wooden clip or twisted
stiff iron wire, and fastening this to a firm standard. Introduce three
or four tablespoonfuls of powdered manganese dioxide (obtainable cheaply
in qr. lbs. at most druggists’), and pour over this spirits of salt
until the flask is one-third full. Into the neck now fit a cork provided
with two circular holes, through one of which a stem funnel passes, and
into the other a glass tube fits tightly, being bent at two right
angles, as shown in Fig. 1. The glass tube may be readily bent by
softening it first over a spirit lamp--the flame being colored distinct
yellow when the glass reaches a pliable state. Slide a 4¹⁄₂-inch disc of
paper (B, Fig. 1) on the free limb of the tube, and also soak several
4-inch circles of cardboard in water. These will make satisfactory
covers for the small glass preserve jars, in which the gas is to be
collected.
[Illustration: FIG. 1.--Apparatus for chlorine experiments.]
(2) _Preparation._--Place one jar beneath the glass tube so that the
latter’s orifice reaches nearly to the bottom, and slide the paper disc
down until it covers the mouth of the jar C. On warming the glass flask
gently with a spirit lamp or, if available, Bunsen gas flame, a
greenish-yellow gas is evolved, and gradually expels the air from flask,
tube, and jar, until this latter is filled with heavy chlorine. The
warming is then interrupted whilst the one jar is removed, covered with
a moist cardboard disc, and replaced by another. The heating again
proceeds, and so on until each remaining jar is successively filled.
[Illustration: FIG. 2.--The unalterable postmark.]
_Chlorine Experiments_ (1).--Damp an addressed envelope, received
through the post, by pressing between sheets of wet blotting-paper, and
stand it in a jar of chlorine with the cover replaced (A, Fig. 2). The
writing ink address will soon begin to fade and finally disappear,
whilst the postmark, which has been impressed in indelible printing ink,
remains unaltered. This reaction shows that chlorine possesses the
valuable property of bleaching writing ink. It may be turned to account
in removing stains from cloth by wetting the spoiled material first and
then standing in a vessel containing the yellow gas (Fig. 3). The fabric
must be quite damp, however, as bleaching only proceeds in the presence
of moisture. Coloring matters, other than black ink, are readily removed
by chlorine, as may be strikingly shown by steeping a wet rose blossom
or bunch of violets in a jar of the gas (Fig. 4); the flowers assume a
transparent waxy appearance, that will puzzle any spectator as to their
real identity.
[Illustration: FIG. 3.--Removing stains from linen by means of
chlorine.]
[Illustration: FIG. 4.--The transparent rose.]
_Chlorine Experiments_ (2).--The energetic gas attacks many substances
spontaneously. If thin blotting-paper be soaked in turpentine, drained,
and dropped into a jar of chlorine, the oil takes fire at once, burning
rapidly amid smoky black fumes. Metals are attacked just as readily as
the inflammable oil of turpentine. Powdered antimony metal or iron
filings shaken into a jar of chlorine scintillate brilliantly with the
evolution of thick white fumes. Similarly Dutch metal leaf, used for
gilding cheap picture frames, ignites in the gas; a salt of copper being
precipitated to the bottom of the jar when the action has ceased.
_All dealings with chlorine should be conducted in a well
ventilated--even draughty--room, and care must be taken not to inhale
the gas._ It corrodes animal tissues just as eagerly as it attacks
turpentine and metals. The gas is very heavy, however, and is therefore
the less difficult to keep under control.
_Niter Paper._--Touch-paper burns quickly, surely, and without flame. It
is prepared by soaking thin tissue paper with a saturated solution of
saltpeter in weak vinegar, and when dry feels rough and crisp to the
touch. Moreover, it burns with a rather pleasant smell. The
advertisement scheme of bygone days, wherein a lighted match was placed
on a particular spot of a paper sheet, and thence the name of the
advertised commodity gradually burnt itself out over the surface, was a
modification of this preparation (Fig. 5). The name or design is simply
drawn with a pointed stump of wood dipped repeatedly in the saltpeter
solution, and the starting-point marked conspicuously by a cross or
black spot. When dry a match is applied to this mark. If there is a
tendency for other parts of the paper than the design itself to burn, a
short immersion in dilute alum solution, when the saltpeter lines have
dried, may be resorted to.
[Illustration: FIG. 5.--A niter paper experiment.]
_Electric Fire._--This compound is in no way of an electric nature,
except that it burns rapidly with brilliant blue illumination. The
constituents are flowers of sulphur, saltpeter, and antimony, four parts
of the former being intermingled with ten parts of powdered saltpeter,
and then one-seventh the total quantity of powdered antimony finally
added. Thorough mixing by gentle stirring must be insured. A good method
of firing the powder is to pack it round a twist of touch-paper in a
small mustard tin, threading the fuse (A, Fig. 6) through a hole in the
lid, so that it may be lighted easily. The mixture burns not only
brightly, but with intense heat--sufficient to melt the thin iron of the
inclosing tin.
[Illustration: FIG. 6.--Lighting electric fire.]
[Illustration: FIG. 7.--A sodium or potassium experiment.]
_The Lightest Element._--Hydrogen is a gas at ordinary temperature, and
has the honor of being the lightest element, for all practical purposes,
known. For this reason it finds wide employment in filling balloons and
airships. The most common methods of preparation consist of decomposing
water or an acid in their several constituents, either by the influence
of electricity or the reaction of a metal. For instance, if a pea’s bulk
of sodium or potassium metal be thrown into a basin of water, A, Fig. 7,
(the experimenter should not bend directly over the vessel), a violent
reaction ensues, the metal decomposes and hustles round the surface as
though in feverish excitement, and in the case of potassium a purple
flame springs up spontaneously. The sodium may also be ignited if it is
thrown on to a floating piece of blotting-paper, or if the water be
thickened with starch. This metal burns with a yellow flame, or rather
colors the hydrogen flame yellow.
[Illustration: FIG. 8.--An interesting hydrogen experiment.]
Preparing hydrogen by the foregoing method is inconvenient and expensive
if any quantity is to be collected, and so in this case the following
plan is usually adopted:--Support a flask (A, Fig. 8), and place zinc
chips (B) in it to the depth of about ¹⁄₄ inch. Fit the mouth with a
cork, through which passes a delivery tube (C) and a “thistle” funnel
(D), dipping nearly to the level of the zinc. When the gas is required,
dilute sulphuric acid--one part oil of vitriol to ten parts water--is
poured down the funnel until the flask is about one-third filled (E).
Five or ten minutes should be allowed after bubbling has commenced
before an attempt is made to light the gas at the delivery tube, as
otherwise air from the flask may be intermingled in the exact proportion
to cause a bad explosion. _No danger need be feared if several minutes
are allowed for the air to be thoroughly dispelled, or, as an additional
measure of safety, a damp towel_ (F) _is wrapped round the flask to
prevent scattering of the glass in the event of a mishap._ The glass
delivery tube should have been softened in a spirit flame and drawn to
a fine point where the hydrogen issues. The gas will be found to burn
with an almost colorless flame.
If a glass tube (A) of larger bore than the delivery pipe be slid over
this latter while the gas burns, a peculiar musical note is
produced--hollow-sounding and shrill (Fig. 9). It is caused by the rapid
succession of slight explosions which constitute the combustion of
hydrogen.
[Illustration: FIG. 9.--A musical flame.]
The extreme lightness of hydrogen, as well as its combustibility, is
well illustrated by blowing a soap bubble. Connect a clay pipe with the
glass delivery tube by means of a length of india-rubber tubing, and
provide this latter with a small clip--tie-clip, for example--so that
the gas supply may be shut off at will (Fig. 10). Let the hydrogen pass
for a minute or so, to clear air out of the clay pipe, and then, having
shut off the gas, dip the pipe bowl into soap-suds. Next open the clip
until the hydrogen has blown the bubble large enough, and then shut off,
shaking the shimmering globe free. It will rise very quickly, just like
an unballasted balloon, and if a lighted taper be applied to its surface
it will explode to annihilation with a loud report.
[Illustration: FIG. 10.--To explode a soap bubble.]
[Illustration: FIG. 11.--Freezing a flask of ammonia to a block of
wood.]
_Spirits of Hartshorn._--Commercial ammonia is actually an aqueous
solution of the gas, which dissolves to an abnormal extent in water.
When it has been absorbed as much as possible the liquid weighs only
22.25 as much as an equal bulk of water, owing, of course, to the
latter’s association with a compound far lighter than itself. So great
is the energy of solution that heat is dissipated from the liquid as
absorption proceeds. Conversely, if the gas be dispelled by blowing air
through strong liquor ammoniac, heat is rapidly absorbed at the expense
of surrounding objects. To show this, stand a small flask in a pool of
water on a wood block, and having about half filled the flask with fresh
ammonia, blow into this through a glass tube connected with the mouth by
a length of rubber tubing (Fig. 11). No long time should elapse before
enough heat has been abstracted from the water to convert it into ice,
so that the flask is frozen firmly to the wood.
Another demonstration of water’s avidity for ammonia gas is afforded by
the following performance. Erect one large flask (A) in an inverted
position, so that the distance between its neck and the table is several
inches greater than its own height. Some distance away, as shown in Fig.
12, erect a small 4-oz. flask (B), and half fill it with a mixture of
four parts sal-ammoniac to three parts slaked lime (C). Fit the neck
with a cork and a delivery tube, which has been so bent as to pass
through a stopper in the mouth and reach nearly to the bottom of a jar
(D) packed with quicklime (E).
Another glass tube (F) issues from this chamber--but only from just
below the cork’s under surface--and passes upwards into the orifice of
the large flask. A square of paper (G, in Fig. 12) is pushed over the
glass tube and presses against the mouth of the flask.
[Illustration: FIG. 12.--To prove water’s affection for ammonia.]
If now the mixture in the 4-oz. flask be warmed, ammonia gas is
produced, and having been robbed of moisture by the quicklime through
which it passes, travels upwards, and collects in the large inverted
flask. When the action has continued for a little while, stop the
heating and remove the delivery tube, and bring an open spirits of salt
bottle near the inverted flask’s mouth. If dense white fumes are
immediately formed, the flask is known to be filled with ammonia gas,
and must be corked up.
[Illustration: FIG. 13.--A novel fountain.]
Beneath this container is next stood another large flask filled with red
litmus solution (A) and fitted with a stopper, through which pass two
glass tubes (M and N, in Fig. 13). One of these (N) is bent outwards,
and extends only just inside the flask’s neck, whilst the other is long
enough to reach from the bottom of the lower flask almost to the top of
that holding the ammonia. Instead of red litmus solution, a liquid made
by boiling red cabbage leaves in water, and adding _just enough_ vinegar
to dispel entirely the bluish coloration, may be used with equal
success.
The position then is that two flasks--of which the upper (B) holds
ammonia gas, whilst the lower retains a pink solution--are supported one
above the other, their necks approaching and joined by a glass tube (M).
A second glass tube (N) also emerges from just above the surface of the
pink liquid, and is bent outwards from the flask, so that it may be held
in the mouth. When this is blown through, the pink water is forced up
the connecting tube (M) and sprays out, fountain-like, within the upper
flask. Moreover, as the ammonia is so rapidly absorbed by the incoming
water, this continually ascends to fill the vacuum, which tends to form
as the gas is dissolved. The fountain continues to play when the blowing
has ceased, and further, although the spray presents a reddish tinge on
entering the flask, it immediately turns blue as the ammonia dissolves
(C, Fig. 13). This reaction indicates the alkalinity of ammonia, such
substances being capable of neutralizing acids, which redden solutions
of vegetable blues.