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Salts of form MASO, and
MASO
HASO, HASO4, H4As2O7

No definite acid of Nb,\ only hydrates

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Nb2O5.xH2O;

most salts are complex, may be represented as xNb2O5.уRO

where

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Remarks.

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Acid not formed from oxide; but aqueous solution of acid boiled gives the oxide.

Oxide dissolves in water to form a solution of the acid.

HVO, HV2O, (also salts V2O, Acids not obtained directly from of form M.VO4) oxide; oxide obtained by heating the acids.

Oxide reacts with water to form the acid; oxide also obtained from the acid by withdrawing water, but not by action of heat.

No oxide known corresponding to acid.

Oxides interact with water to form the acids; oxides not obtained by heating the acids.

Solution of oxide in water interacts with alkalis &c. to form salts. Acids not obtained from the oxide by action of water; oxide is obtained by heating the acids.

Nb2O5 Oxide obtained by heating the hydrates; hydrates not obtained directly from the oxide.

RO=K,O, CaO, &c.

H,SbO, (also salts of form Sb2O3 Acid not obtained directly from MSbO2) oxide; oxide formed by heating the acid.

HSbO, H3SbO4, H4Sb2O, Sb2O5 Acids not obtained directly from oxide; oxide formed by heating the acids.

HTa2O (also salts of Ta2O Acid not obtained directly from form MTaÒ, and various oxide; oxide produced by heating complex salts the acid.

xTa2O5.уRO)

No acids, or salts derived from acids, of didymium, erbium, or bismuth, have been isolated.

*The symbol Aq here signifies that the acid to the formula of which it is added exists only in aqueous solution, and has not been isolated as a solid.

Hyponitrous acid (HNO) and nitrous acid (HNO) act as reducing agents; they readily combine with oxygen to produce nitric acid. Nitric acid on the other hand is very frequently used as an oxidiser; when heated it is decomposed to water, oxygen, and nitrogen dioxide (2HNO, H2O+ 2NO, + O). All the nitrogen acids are monobasic.

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When aqueous solutions of hypophosphorous acid (HPO) and phosphorous acid (H.PO) are boiled, phosphine (PH) is evolved, and phosphoric acid (H,PO) remains in solution. The three phosphoric acids, ortho- H.PO,, meta- HPO, and pyro- HP,O,, may be formed by adding water to phosphoric anhydride PO, (s. Chap. XI., par. 215). Hypophosphorous acid is monobasic, and phosphorous acid is dibasic. Of the three phosphoric acids, orthophosphoric H.PO,, forms the largest number of definite salts: sodium pyrophosphate, Na P,O,, is obtained by heating ordinary sodium phosphate (2Na HPO = H2O + Na P,O,); sodium metaphosphate, NaPO, may be obtained by heating sodium-ammonium phosphate (Na(NH)HPO1 = H2O + NH2+ NaPO1). When orthophosphoric acid is heated to 230° or so pyrophosphoric acid is obtained (2H,PO1 = H2O + H ̧P2O,), at a red heat metaphosphoric acid is produced (H POHO+HPO). When metaor pyro-phosphoric acid is boiled with water orthophosphoric acid is produced.

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Metavanadic acid HVO,, and pyrovanadic acid HVO,, are prepared, indirectly, from salts of these acids. Besides the salts of these acids, numerous polyvanadates (or condensed vanadates) exist; the following are given as examples, Na VO, SrVO 119

16°

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"No arsenious acid has been isolated. An aqueous solution of arsenious oxide (As,O,) may contain arsenious acid; when this solution is neutralised with soda the salt NaAsO, is obtained; by adding silver nitrate to an aqueous solution of As,O,, Ag,AsO, is precipitated. The arsenites are unstable salts, their composition seems to change with small variations in the conditions of their formation. Arsenic acid, H ̧AsО, is formed by oxidising As,O, in presence of water, either by nitric acid or by chlorine, and crystallising. This acid loses water at 150° or so with formation of pyro-arsenic acid (2H ̧AsO1 = H2O + H ̧As̟ ̧O,), and at about 210° water is again evolved and meta-arsenic acid remains

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2

(H ̧As2O, = H2O + 2HAsO2).

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432

Both meta- and pyro-arsenic acids are at once changed to the ortho-acid by solution in water.

Antimonious oxide dissolves in hot caustic soda solution; from this solution the salt NaSbO, is obtained on cooling. Ortho-antimonic acid H,SbO, is produced, indirectly, from tartar emetic, KSbCH,O,. The antimonites are easily oxidised; they are unstable and easily undergo change.

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Antimonic acid, H,SbO, is obtained by adding a little water to SbCl, and drying the solid thus obtained over sulphuric acid; at 100° water is evolved and pyro-antimonic acid, H,Sb,O,, remains, and at 200° this acid again loses water with production of meta-antimonic acid, HSbO3. These acids seem all to exist in aqueous solution; salts derived from HSbO, and HSb,O,, but not from H,SbO, are known.

Salts are obtained by replacing the hydrogen of various acids by the elements vanadium, didymium, erbium, or bismuth. The salts of didymium and erbium have not been much studied; they seem to belong to the form M,3X, where X=SO1, 2NO,, &c. Vanadium pentoxide, V.O, interacts with alkalis to produce salts of the form MVO; but it also interacts with sulphuric acid, and with a few other acids, to produce basic salts, e.g. (VO),(SO4)3° Vanadium tetroxide, V2O, also interacts with sulphuric acid to form the salt vo.so,

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Bismuthous oxide, Bi̟ O̟, forms a series of salts by interacting with acids; these salts belong to the form Bi,3X (X=SO,, 2NO,, PO,, &c.), e.g. Bi 3SO, Bi,6NO,, BiPO BIASO,. Most of these salts are decomposed by water with formation of basic salts; the composition of some of these basic salts is represented by the general formula BiOX where X-NO2, SO,

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4, &c.; but many others are more complex, and their composition can be expressed only by such a formula as xBi̟ ̧ ̧.yR.zH2O where Ran acidic oxide, e.g. NO, SO ̧

2

&c.

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433 The elements of Group V. shew a gradual change of properties from the decidedly negative nitrogen to the metallic bismuth. Various small sub-classes appear in the group; thus arsenic and antimony are very closely related; so are niobium and tantalum; nitrogen and phosphorus also are very similar in many chemical properties. Vanadium appears to be more distinctly metallic in its chemical properties than the

elements which succeed it in the even-series, but it is to be remembered that the properties of these elements have been very imperfectly investigated. The group cannot be divided into two families comprising the even-series and odd-series elements, respectively. Although it cannot be said that all the elements shew marked similarities, yet the group-character is impressed on them all. All the elements of this group are distinctly more like each other than they are like the elements of any other group.

Group I. presents a number of elements some of which are very similar in their chemical properties, while others are so different from these and from one another that it seems at first sight quite a mistake to place them in the same group.

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435

Group I.

Even-series elements, and second member of oddseries

Atomic weights

2

Even series. Li=7.01

Sp. grs. (approx.)
Melting points
(approx.)

1

Odd series. H=1

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CHAPTER XXII.

THE ELEMENTS OF GROUP I.

4
K=39.04

6
8
Rb=85.2 Cs=132.7

3

5

Na=23

Cu=63.2

LITHIUM.

180°

11.9

⚫941

Silver-white;
very soft; fairly
ductile; not
very tenacious;
not volatile at
red-heat.

SODIUM.

Silicate and
phosphate
occur with same
salts of other
metals of the .
family.
Compounds are
widely distri-
buted, but in
small quanti-
ties, in rocks,
water, plants,
and some ani-
mal secretions.
Prepared by
electrolysing
fused mixture
of LiCl and
NH4Cl.
Combines di-
rectly with oxy-
gen, but not so
rapidly as other
elements of the
family.
Decomposes
cold water
giving LiOHAq
and H.

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POTASSIUM.

Oxidises rapidly in air. Decomposes cold water rapidly with evolution of H and production of NaOHAq.

7.01

23

39.04

85.2

132.7 The molecular weights of sodium and potassium are the same as their atomic weights; the other elements of the family have not yet been gasified, and therefore their molecular weights are unknown.

*59

*98 95°.5

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Ag=107.66

*87

58° 62°

44.9

•166
White; soft;
brittle at 0°;
malleable at
abt. 5°; pasty at
15°; can be dis-
tilled at 700°-
800°.
Nitrate, sul-
phate, silicate,
&c. occur in
large quantities
widely distri-
buted.
Prepared by de-
oxidising K2CO3
by hot carbon.

RUBIDIUM.

Oxidises very
rapidly in air.
Decomposes
cold water very
rapidly with
production of
KOHAq and
H; H usually
takes fire.

10

1.52 38°

9

56.1

not determined.
Silver-white:
soft as wax at
-10°

Compounds
occur very
widely distri-
buted, but in
very small
quantities, in
most minerals
containing salts
of K and Na.
Prepared by de-
oxidising
RbqCO by hot
carbon.

Oxidises so ra-
pidly in air that
usually takes
fire.

Very rapidly de-
composes cold
water, giving
RbOHAq
and H.

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|

11

Au=197

CAESIUM.

1-88 26° - 27°

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