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Acid.
Corresponding

Remarks.
Oxide.
HNOAq*

NO Acid not formed from oxide; but

aqueous solution of acid boiled

gives the oxide. HNO.AZ

1,02 Oxide dissolves in water to form a

solution of the acid. HNO3

NOG Oxide reacts with water to form the

acid; oxide also obtained from the acid by withdrawing water,

but not by action of heat. H.H,PO,Aq

No oxide known corresponding to

acid. HZ.HPO,Aq P,03! Oxides interact with water to form HPO3, H.PO., HP,0, PCOS the acids; oxides not obtained

by heating the acids. HVO3, H.V,0, (also salts V,05 Acids not obtained directly from of form M,V04)

oxide; oxide obtained by heating

the acids. Salts of form MAso, and As,0g Solution of oxide in water interacts M,AsOy

with alkalis &c. to form salts. HAsO3, H.AsO4, H.As,O, As,O, Acids not obtained from the oxide

by action of water; oxide is

obtained by heating the acids. No definite acid of Nb, only hydrates

Nb, 0.61,0; Nb,05 Oxide obtained by heating the hy. most salts are complex,

drates; hydrates not obtained may be represented as

directly from the oxide. «Nb,05.yRO where

RO=KO, CaO, &c. H2SbO2 (also salts of form Sb,02 Acid not obtained directly from MSb02)

oxide; oxide formed by beating

the acid. HSb03, H2Sb04, H,Sb,O, Sb,0, Acids not obtained directly from

oxide; oxide formed by heating

the acids. H,Ta,0, (also salts of Ta,0, Acid not obtained directly from form MTad, and various

oxide; oxide produced by heating complex salts

the acid. xTa 05.YRO)

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, = H,0 + 2NO, +O). All the nitrogen acids are monobasic.

When aqueous solutions of hypophosphorous acid (H. PO,) and phosphorous acid (H.PO.) are boiled, phosphine (P8) is evolved, and phosphoric acid (H,PO.) remains in solution. The three phosphoric acids, ortho- H PO, meta- HPO,, and pyro- H P,0,, 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,0,, is obtained by heating ordinary sodium phosphate (2Na HPO, = H,0 + Na P,0z); sodium metaphosphate, NaPO, may be obtained by heating sodium-ammonium phosphate (Na(NH2HPO = H2O + NH + NaPO). When orthophosphoric acid is heated to 230° or so pyrophosphoric acid is obtained (2H PO = H,0+ H P,0,), at a red heat metaphosphoric acid is produced (H PO =X0+ HPO,). When metaor pyro-phosphoric acid is boiled with water orthophosphoric acid is produced.

Metavanadic acid HVO, and pyrovanadic acid H.V.0,, 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 V O,,, SrVO

No arsenious acid has been isolated. An aqueous solution of arsenious oxide (As 03) 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 Oy, 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, AsO is formed by oxidising Aso, 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_AsO,= H,0+ H As,O), and at about 210° water is again evolved and meta-arsenic acid remains

(H,As,0,= H,0 + 2HAsOz).

16

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 NaSb0, is obtained on cooling. Ortho-antimonic acid H,SbO, is produced, indirectly, from tartar emetic, KSbC,H,O,. The antimonites are easily oxidised; they are unstable and easily undergo change.

Antimonic acid, H Sb0, 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,On, remains, and at 200° this acid again loses water with production of meta-antimonic acid, HSbO. These acids seem all to exist in aqueous solution ; salts derived from HSbOg and H Sb, 0,, 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=SO, 2NO,, &c. Vanadium pentoxide, vos interacts with alkalis to produce salts of the form M VO ; but it also interacts with sulphuric acid, and with a few other acids, to produce basic salts, e.g. (VO),(SO )3.

Vanadium tetroxide, VO, also interacts with sulphuric acid to form the salt

Bismuthous oxide, Bi, 0, forms a series of salts by interacting with acids; these salts belong to the form Bi 3X (X=80, 2NO, PO,, &c.), e.g. Bi 350, Bi6NO,, BIBO 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=NO, SO.

4, &c.; but many others are more complex, and their composition can be expressed only by such a formula «Bi,O, YR. H,0 where R ==an acidic oxide, e.g. NO, SO, &c.

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

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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.

434

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lodd series.

2
4
6
8
10

12
Even series. Li=7.01 K=39.04 Rb=85.2 Cs=132.7
Group I.

1
3
5
7
9

11
H=1 Na=23 Cu=63.2 Ag=10766

Au=197 Even-series elements, and second mem- LITHIUM

SODIUM.

POTASSIUM. RUBIDIUM. CAESIUM. ber of odd.

series Atomic weights

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. Sp. grs. (approx.)

59

.98
.87
1.52

1.88
Melting points
180°

950-5
58–62°

38°

269-27° (approx.) Atom. weights

11.9

23.5
44.9
56-1

90-6
spec. grave.
Sp. heats

.941

293

166 not determined. not determined. Appearance and Silver-white; Silver-white; White; soft; Silver-white; Silver-white; general physical very soft; fairly soft; very duc- brittle at 0°; soft as wax at soft. properties. ductile; not tile at 0°; can be malleable at -10°

very tenacious; distilled at red- abt. 5o; pasty at
not volatile at heat.

15°; can be dis-
red-heat.

tilled at 700° —

800°. Occurrence and Silicate and Chloride, sili- Nitrate, sul- Compounds Silicate occurs preparation. phosphate cate, fluoride, phate, silicate, occur very as a rare mine

occur with same nitrate, &c., &c. occur in widely distri- ral.
salts of other occur in large large quantities buted, but in Minute quanti-
metals of the quantities widely distri-

very small

ties of some family. widely distri- buted.

quantities, in compounds Compounds are buted.

Prepared by de- most minerals occur in many widely distri- Prepared by oxidising K2CO3 containing salts rocks and buted, but in deoxidising by hot carbon. of K and Na. waters. small quantiNa2CO3 by hot

Prepared by de- Prepared by ties, in rocks, carbon.

oxidising electrolysing water, plants,

Rb2C0g by hot fused caesiumand some ani

carbon.
mal secretions.

nide.
Prepared by
electrolysing
fused mixture
of LiCl and

NH4Cl. General chemical Combines di- Oxidises rapidly Oxidises very Oxidises so ra- Exceedingly properties. rectly with oxy- in air.

rapidly in air. pidly in air that rapidly and gen, but not so Decomposes Decomposes

usually takes completely oxirapidly as other cold water ra- cold water very fire.

dised in air. elements of the pidly with evo- rapidly with Very rapidly de- Properties not family.

lution of H and production of composes cold yet much invesDecomposes production of KOHAq and water, giving tigated. cold water NaOHAq. H; H usually RbOHĂq giving LiOHAT

takes fire.

and H. and H.

barium cya

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