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The molecular weight of nitrogen is 28-02; the molecular weights of the other elements are unknown. Sp. grs. (approx.) .97 if air=1; liquid; s.G.="885

5.5

7 (?)

not determined.

not determined.

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6.5 (?)

*0456

11 (?) not determined.

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NIOBIUM.

DIDYMIUM*.

TANTALUM.

94

144

182

Sp. heats

Atom. weights

spec. gravs.

Occurrence and preparation.

Appearance, and

general physical properties.

The melting points of most of these elements have not been determined.

In large quantities in air.

Many compounds, especially ammonia and nitrates, also occur in large quantities and widely distributed. Prepared by removing O from air.

Colourless,

In a few minerals, not widely distributed, chiefly as oxides and sulphides.

Prepared by long continued heating VCl2 in hydrogen.

tasteless, odour- line, powder.
less, gas.

Liquefied at

very low tem

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Grey, crystal

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perature and

under great

General chemical properties.

pressure; liquid boils at abt. 195°. Combines directly with few if any elements at ordinary temperatures; but at very high temperatures combines directly with B, Si, Cr, Mg, V, and a few other elements. If electric discharge is passed through mixture of N with O, or H, a very little NO2, or NH3, is formed. Strongly nega

tive. Oxides are generally anhydrides.

Hydride, NH3,

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*There is some doubt whether the body known as didymium is or is not a mixture of two or more elements; many of the properties of compounds of didymium are probably the properties of mixtures.

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Appearance, and general physical properties.

General chemical properties.

425

Many phos-
phates occur
very widely dis-
tributed in
rocks and
waters; also in
bones and in
parts of plants.
Compounds
P with C, N, and
O occur in nerve
and brain
matter.
Prepared by
heating
Ca(PO3)2 with
charcoal.

of

Soft wax-like
solid.
Crystalline.
Non-conductor
of electricity.

Burns in air to
P20 and P205.
Combines di-
rectly with Cl,
Br, and I.
Oxidised by
HNO3.
Does not form
salts by inter-
acting with
acids.
Hydride, PH3,
resembles NH
but is less alka-
line.
Oxides are
anhydrides.
Atom trivalent
and pentavalent
in gaseous
molecules.
Phosphorus
shews allotropy
(s. Chap. XI.,
par. 220).

5.7

500° (under
pressure)

13.2

⚫083

As2O3 and
AsQSg occur;
also compounds
of As with Te
and S, with Ni,
Co, &c. occur in
small quantities
widely distri-
buted.
Prepared by
heating AS203
with charcoal.

Grey, hard,
brittle, solid.
Crystalline.

Fair conductor
of electricity.

18
⚫053

Chief naturally
occurring com-
pound is Sb2S3;
found in com-
paratively small
quantities in
very various
parts.
Prepared by
heating Sb2O3
with charcoal.

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not determined.
Er20g occurs in
small quantities
in ytterbite, a
Swedish min-
eral.

*0308

Bismuth is found native; also Big03 and BigS3, &c., but not in large quantities.

Metal not yet Prepared by

obtained.

heating BigO3

Oxide, Er203, is
basic, forming

salts, e.g.

Er23SO4
No hydride
known.
No oxide known
to act as an an-
hydride.
No compound
yet gasified.

with charcoal.

Grey, with faintly reddish tinge; crystallises easily; brittle.

Bad conductor
of electricity.

Burns in air to
BigO3.
Combines di-
rectly with Cl,
Br, and I.
Oxidised by
HNO3, and at
same time
Bi.3NOg is
formed.
Many salts
known derived
from acids.
No hydride
known.

Oxides are
basic; Bi205
shews very
slight acidic
functions.
Atom trivalent
in gaseous
molecules.

General formulae and chemical characters of compounds of elements of Group V.

Hydrides. MH; M = N, P, As, Sb.

Oxides. MO; M=N, V. M,O,; M = N, V, Nb, Bi.
MO; M = any metal of the group except Nb and Ta. M2O;
M=N, P, V, Nb, Sb, Ta, Bi. M,O,; Many element of the

group except Er. Hydrates of many of these oxides are known.

Sulphides. No sulphides of niobium or erbium have yet been prepared. M.S.; M = any element of the group except N, Ta, (Nb or Er). M,S,; M = P, V, As, Sb. A few other sulphides are known, e.g. N,S,, Ta,S,

Haloid compounds. No haloid compounds of erbium have yet been prepared; the haloid compounds of nitrogen are very unstable and explode with great violence, their composition is still doubtful.

MX,; M = any element of the group except Ta (? N) or Er. MX; M = P, Nb, Sb, Ta; X = Cl and in some cases also Br or I. A few other haloid compounds exist, e.g. PL VCI

Acids. The following are the chief compounds of hydrogen with oxygen and an element of Group V. which are acids (when Aq is added to a formula it indicates that the acid is known only in aqueous solution).

HVO

HNOAq, HNO Aq, HNO. H.PO,Aq, H.PO,Aq, HPо,
HPO,, HP,O,
HV2O. HASO,Aq, HASO,
H ̧ASO, HA§,0,. HSbo, HsbО,, H,Sbo, HSь ̧O..

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Salts. The only elements of the group which are known to form series of definite salts by replacing the hydrogen of acids are vanadium, didymium, erbium, and bismuth. The salts of vanadium are all basic salts, they belong for the most part to the series VOX and (VO),X,; the salts of didymium and erbium belong to the series M,3X; the normal salts of bismuth belong to the series Bi,3X, but besides these a great many basic salts exist. (X = SO, 2NO, &c.). Antimony forms a few compounds which may be regarded as basic salts, especially aSb,O,.ySO, and xSb,O,.yN,O,; tartar-emetic, KSьCHO,, is probably to be classed as a double antimonypotassium salt.

3

3

3

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The following are the principal compounds of elements of 426 Group V. which have been gasified, and the relative densities of the vapours of which have been determined; NH, PH2 ASH, PC, PI, PF, VCI,, AsCl, AsI, NbCl,, SbCl, SbI, TaCl, BiCl. The statements made in the table in par. 424 regarding the valencies of the atoms of the elements of Group V. are based on the existence and compositions of these gaseous molecules.

Arsenious and antimonious oxides have been gasified; the

427

compositions of the gaseous molecules of these compounds are expressed by the formulae As,0, and SbO. The formulae of the following oxides of nitrogen are molecular N,O, NO, NO, NO. A few oxychlorides, e.g. NbOCI,, have also been gasified.

6

The formulae of the other compounds are not necessarily molecular; they are the simplest formulae that can be given, consistently with the determined values of the atomic weights of the elements, and with the reactions of the compounds.

The hydrides MH, are gases under ordinary conditions. Ammonia, NH, is obtained in small quantities by the direct union of nitrogen and hydrogen under the influence of the induced electric discharge; also in many reactions in which hydrogen is produced in contact with nitrogen, e.g. when steam and nitrogen are passed over hot iron, or when nitrogen is produced in contact with hydrogen, e.g. when hydrogen and nitric oxide are passed over hot finely divided platinum. Ammonia is usually prepared by heating a mixture of ammonium chloride and lime;

2NH,C1+CaO= CaCl,+H,O + 2NH.

2

Phosphoretted hydrogen or phosphine, PH, may be obtained by heating a mixture of phosphonium iodide and an alkali; PH ̧I + KOHAq = KIAq + H2O + PH1; it is however more usually prepared by heating a solution of an alkali with phosphorus; 3KOHAq + 3H2O + 4P = 3KH,PO,Aq + PH ̧ (potassium hypophosphite remains in solution, phosphine is evolved as a gas).

Arsenuretted hydrogen or arsine, AsH,, is obtained by producing hydrogen in contact with a solution of an arsenic compound. Antimonuretted hydrogen, or stibine, SbH, is obtained by a similar method. Thus,

=

M ̧ ̧Aq+жM ̧O̟ ̧Aq+12H+∞H=2MH ̧+3H ̧O+H+M ̧O̟ ̧Aq
(the hydrogen must be produced in contact with the M2O,Aq; M = As or Sb).
Ammonia, NH,, combines with most acids to form am-
monium salts; e.g. NH, + HCl = NH,C1; 2NH2+ H2SO
(NH),SO. Phosphine, PH,, combines with hydriodic acid,
and with hydrochloric acid under increased pressure, to form
phosphonium salts; e.g. PH + HI= PHI. (Regarding ammo-
nium salts s. Chap. XI. pars. 210, 211, and Chap. XVII.
par. 371.) Arsine and stibine do not combine with acids.

3

The hydrides MH, can be oxidised to oxides and water; ammonia is oxidised by mixing it with much oxygen and

2

bringing a flame to the mixture; water, nitrogen, and a little ammonium nitrate (NH.NO) are formed; phosphine is oxidised to phosphorus pentoxide (P,O,) and water by mixing it with air or oxygen and raising the temperature; arsine and stibine are oxidised by mixing with air or oxygen and bringing a flame to the mixture; if much oxygen is present the products are water and arsenious or antimonious oxide; if little oxygen is present, water, arsenic or antimony, and a little arsenious or antimonious oxide, are formed.

Arsine and stibine are decomposed by heat; ammonia and phosphine are much more stable towards heat.

The most important and best studied oxides of the 428 elements of Group V. are those whose composition is expressed by the formulae MO, and M,O,, respectively.

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The trioxides MO, may be formed by the direct union of their elements; Nb,O, and Ta,O, have not yet been prepared, and as erbium has not been isolated it is uncertain whether the oxide Er.O, would or would not be formed by heating erbium in oxygen. Nitrogen and oxygen combine only when a mixture of the gases is submitted to the continued, action of electric sparks, and then only a small quantity of NO, is formed; the other elements of the group are readily oxidised to M,O, by heating in air or oxygen.

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The oxides M2O, may be divided into three classes: (1) acidic oxides, NO, PO; (2) basic oxides, Di,O,, Er,O,, Bio,; (3) oxides which are both acidic and basic, As,O,, Sb,O, (? V2O). The oxides NO, and P,O, dissolve in water to form solutions of nitrous acid HNO,, and phosphorous acid H.PO, respectively; neither oxide shews the smallest tendency to interact with acids and form salts. The oxides Di̟ ̧O,, Er2O,, and Bi, interact with acids to produce salts; they are all insoluble in, and unchanged by contact with, water. Arsenious oxide, As,O,, dissolves in water and the solution interacts with caustic soda or potash to form salts of the composition MASO, (M = Na or K); but no oxyacid derived from As,O, has been obtained. Antimonious oxide, Sb,O,, is slightly soluble in water and the solution reacts with potash or soda to form antimonites M.SbO,; the acid H.SbO, is known as a solid, but it is not obtained by the direct interaction of water with SbO. Arsenious oxide interacts with concentrated hydrochloric acid to form arsenious chloride, AsCl,; it is also said to form a salt ASKC,H,O, by reacting with solution of potassiumhydrogen tartrate; antimonious oxide forms SbCl, by reacting

M. E. C.

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