An Introduction to Chemical Science

coal, bituminous coal, cannel

paratio

examine the deposit. It is carbon, i.e. lamp- black or soot, which is a constituent of gas, or of the candle. Open the valve at the base of the Bunsen

e the combustion and the smoke, if any. Try

. CO2 is an invisible gas. The porcelain, when held in the flame, cools the C below the point at which it

e candle? The same two are found in wood and in gas. Experiment 29.-Put into a small Hessian crucible (Fig. 18) some pieces of wood 2 or 3 cm long, cover with sand, and heat the crucibl

d heat till the sugar is black. C is left. See Experiment 5. R

graphite, and amorphous -not crystalline-carbon. The latter includes charcoal, lamp- black, bone-black, gas carbon, coke, and mineral coal. All these forms of C h

nt often has of appearing under various forms, with diff

a mineral.] When heated in the electric arc, at very high temperatures, diamond swells and turns black. 43. Graphite, or Plumbago, is One of the Softest Minerals.-It is black and infusible, and oxidizes only at very high temperatures, higher than the diamond. It contains from 95 to 98 per cent C. Grap

on comprises the f

The volatile gases are thus driven off from the wood; what is left is C, and a

, naphtha, and various oils, and collecting the C of the smoke. It is used for mak

lling bones, i.e. by heating them in retorts into wh

f the gas-house. See page 182. It is

covered the earth as they do to-day. In certain places they slowly sank, together with the land, into the interior of the earth, were covered with sand, rock, and water, and heated from the earth's interior. A slow distillation took place, which drove off some of

ds being in the United States. From the nature

0 to 95 per cent. This represents most complete distillation in the earth;

ter part of the coal in the earth is bituminous. It represents incomplete distillation. Hence, by art

ted like a candle. This is because so many of the gases are still

ccurring forms of this element, in the order of their purity. Carbon forms the basis of all vegetable a

Reduci

its bulk of powdered charcoal. Heat strongly for ten or fifteen minutes. Examine the contents for metallic copp

rom a compound. C is the most common and important reducing agent, being u

ives up its O to a reducing agent. What

a Deco

ghly, covering the bottle with the hand. Then pour the whole on a filter paper, and examine the filtrate. If all the col

l is used in large quantities for decolorizing sugar. The coloring matter is take

H2S3 i.e. hydrogen sulphide, in water, instead of cochineal solution

taken in at the same time from the air, and these gases are there oxidized and rendered odorless and harmless. For this reason charcoal is muc

r of Gases and a

per. Cover it well with bone-black, and look for combustion after a while. O has been conden

LE

some one or more points of attraction. Suppose the latter to be true, each atom must have one or more poles or bonds of attraction, like the poles of a magnet. Different elements differ in their number of bonds. Na has one, which may be written graphically Na-; Cl has one, -Cl.

y numerous, and, in fact, we do not know that atoms have bonds at all; but we can best explain the phenomena by supposing them

umber of bonds, one, is taken as the unit. Valence has always to be taken into account in writing the symbol

ry of bonds shows why an atom cannot exist alone. It would have free or unused bonds, and hence must combine with its fellow to form a molecule, in case of an element as well as in that of

and have been found to correspond to the symbols MgCl2 and NaCl. This will be better understood after studying the chapter on atomic weights. In writing the symbol for t

e union of Zn and O

atom with atom,

ariable quantivalence. Sn has either 2 or 4; P has 3 or 5. It usually varies by two for a given element, as though a pair of bonds sometimes saturated each other;. e.g. =Sn=, a quantivalence of

d that the quantivalence of Fe is 3, but the graphic symbol shows it to be 4.

Cl-Fe-Fe-C

two oxides of iro

nds HNO3 or KNO3; (SO4) in H2SO4. In HNO3 the radical has a valence of 1, to balance that of H, H-NO3). In H2SO4, what is the valence of (SO4)

a is a dyad, Ca==(P04). The least common multiple of the bonds (2 and 3) is 6, which, divided by 2 (no. Ca bonds), gives 3 (no. Ca atoms to

and (NO3), K and (SO4), Mg and (PO4), Fe and (SO4) (both valences of Fe),