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Odd-series PHOSPHORUS. ARSENIC.

ANTIMONY. ERBIUM.

BISMUTH. elements Atomic weights 30.96

74.9

120
166

208 Molecular weights 123.84 and 61.92 299•6 and 149:8 ?360 or 240

-unknown Sp. grs. (approx.) 1.9

5.7
6.7

9.9 Melting points 45°

500° (under
430°

270° (approx.)

pressure) Atomic weights

16.3
13.2
18

20:5 spec. graus. Sp. heats

202
•083
053 not determined.

*0308 Occurrence and Many phos

As203 and

Chief naturally Er203 occurs in Bismuth is preparation. phates occur As Sz occur; occurring com- small quantities found native;

very widely dis- also compounds pound is Sb2S3; in ytterbite, a also Bi203. and tributed in of As with Te found in com- Swedish min- Bi,S3, &c., but rocks and and S, with Ni, paratively small eral.

not in large waters; also in Co, &c. occur in quantities in

quantities. bones and in small quantities very various Metal not yet Prepared by parts of plants. widely distri- parts.

obtained. heating Bizog Compounds of buted. Prepared by

with charcoal.
P with C, N, and Prepared by heating Sb2O3
O occur in nerve heating As203 with charcoal.
and brain

with charcoal.
matter.
Prepared by
heating
Ca(PO3)2 with

charcoal.
Appearance, and Soft wax-like Grey, hard, Grey, lustrous,

Grey, with general physical solid.

brittle, solid.
brittle, very

faintly reddish properties. Crystalline. Crystalline. crystalline,

tinge; crystalNon-conductor Fair conductor solid.

lises easily; of electricity. of electricity. Fair conductor

brittle. of electricity.

Bad conductor

of electricity. General chemical Burns in air to Burns in air to Burns in air to Oxide, Er208, is Burns in air to properties. P203 and P205. As203.

Sb203

basic, forming Bi203. Combines di- Combines di- Combines di- salts, e.g.

Combines directly with ci, rectly with ci, rectly with Ci, Er23504. rectly with CI, Br, and I.

Br, and I. Br, and I. No hydride Br, and I.
Oxidised by Oxidised by Oxidised by known.

Oxidised by
HNO3.
HNO3.
HNO3.

No oxide known HNO3, and at
Does not form No salts known A few salts de- to act as an an- same time
salts by inter- derived from rived from acids hydride. Bi.3N03 is
acting with
acids.

seem to exist. No compound formed. acids.

Hydride, AsH3, Hydride, SbHz, yet gasified. Many salts Hydride, PH3, is scarcely if at not alkaline.

known derived resembles NHg all alkaline. Oxides are

from acids. but is less alka- Oxides are anhydrides, but

No hydride line. anhydrides. also slightly

known. Oxides are Atom trivalent basic.

Oxides are anhydrides. in gaseous Atom trivalent

basic; Bi205 Atom trivalent molecules. in gaseous

shews very and pentavalent Arsenic exists molecules.

slight acidic in gaseous in allotropic

functions. molecules. forms (s. Chap.

Atom trivalent Phosphorus XI., par. 222).

in gaseous shews allotropy

molecules. (8. Chap. XI.,

par. 220).
425 General formulae and chemical characters of compounds of

elements of Group V.
Hydrides. MH,; M=N, P, As, Sb.

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Oxides. M,0; M=N, V. M,0,; M = N, V, Nb, Bi.
M,O,; M=any metal of the group except Nb and Ta. M,O,
M= N, P, V, Nb, Sb, Ta, Bi. M,0,; M = any element of the

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

Sulphides. No sulphides of niobium or erbium have yet been prepared. M.Ss; 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. P,1., voi

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).

HNOAq, HNO AY, HNOz. H PO,Aq, H,PO,Aq, H2PO4, HPO, HP,O, HVO, HVO H Aso, Aq, "HÅSOM ,

. ? , , HASO, HASO, H Sbo, Hsbon, H.,860," H,Sb,0,

,'. H Ta,O,

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 = SOC, 2NO3, &c.). Antimony forms a few compounds which may be regarded as basic salts, especially «Sb,02:YSO, and «Sb,0z.YN,05; tartar-emetic, KSC,H,O,, is probably to be classed as a double antimony. potassium salt.

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,,

PH, AsH, PCI,, PI,, PF;, VCI,, AsCl, AsIy, NbCl,, SbCl,, Sbly, 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

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

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.

Ammónia, 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,Cl + CaO = CaCl, +H,O+2NH,. Phosphoretted hydrogen or phosphine, PH, may be obtained by heating a mixture of phosphonium iodide and an alkali; PH, I + KOHAq = KIAq+H,O+PH ; it is however more usually prepared by heating a solution of an alkali with phosphorus; 3KOHAq + 38,0 + 4P = 3KH PO, Aq + PH,

3H (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,O,Aq+XM,O,Aq+12H+xH=2MH+3H,0+H+xMO,Aq (the hydrogen must be produced in contact with the M,OzAq; M=As or Sb).

Ammonia, NH, combines with most acids to form ammonium salts; e.g. NH, + HCl = NHCl; 2NH, +H SO,= (NH),SO, Phosphine, PH, combines with hydriodic acid, and with hydrochloric acid under increased pressure, to form phosphonium salts ; e.g. PH, +HI = PH.I. (Regarding ammonium salts 8. Chap. XI. pars. 210, 211, and Chap. XVII. par. 371.) Arsine and stibine do not combine with acids.

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

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bringing a flame to the mixture; water, nitrogen, and a little ammonium nitrate (NH.NO,) are formed; phosphine is oxidised to phosphorus pentoxide (P,03) 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 M,0, and M,0g, respectively.

The trioxides M0, may be formed by the direct union of their elements; N5,0, 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 N, O, is formed; the other elements of the group are readily oxidised to MO by heating in air or oxygen.

The oxides M,0, may be divided into three classes: (1) acidic oxides, N, O, P; (2) basic oxides, Di, Oy, Er, 03, BI,03; (3) oxides which are both acidic and basic, As Oy,

Sb, (?V,0z). The oxides NO, and P. O, dissolve in water to form solutions of nitrous acid ÅNO, and phosphorous acid H,PO,, respectively; neither oxide shews the smallest tendency to interact with acids and form salts. The oxides Di, 03, Er, 0 and Bi,O, interact with acids to produce salts; they are all insoluble in, and unchanged by contact with, water. Arsenious oxide, As,Og, dissolves in water and the solution interacts with caustic soda or potash to form salts of the composition M, AsOz (M = Na or K); but no oxyacid derived from As, Oz has been obtained. Antimonious oxide, Sb,Os, is slightly soluble in water and the solution reacts with potash or soda to form antimonites M Sb0g; the acid H.Sb0, is known as a solid, but it is not obtained by the direct interaction of water with Sb O, Arsenious oxide interacts with concentrated hydrochloric acid to form arsenious chloride, AsCl,; it is also said to form a salt AsKC H0, by reacting with solution of potassiumhydrogen tartrate; antimonious oxide forms Sbci, by reacting M. E. C.

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with concentrated hydrochloric acid, it forms SbKC,H,O, by dissolving in KHCHO.Aq and crystallising, and it probably interacts with concentrated sulphuric acid to form Sb,(SO2).. Vanadium trioxide V,0, is said to interact with acids to produce a series of unstable, easily oxidised, salts.

The pentoxides, M.O, can be obtained by heating the elements in oxygen when M=P, V, Nb, or Ta; by evolving oxygen in contact with M,0g when M = As, Sb, Di, or Bi; and by withdrawing water from nitric acid in the case of NO.(2HNO, -H,O=N,0).

The oxides No, and P,0, dissolve in water to form acid solutions from which the acids HNO, (from N.0), HPO, H PO, and H.PO, (from P,0) can be obtained. The oxides As, O, and Sbo, are slightly soluble in water forming acid solutions from which salts can be obtained, e.g. Ag, Aso, KSb0,; V O, is scarcely soluble, Nb,05, Tals, Di, 0,, and Bi, O. are insoluble, in water; salts of the formsRMIVO, ŠTaO,, and M.Nb, 0, &c. are obtained by heating the pentoxides of V, Ta, and Nb, with molten potash or soda; no salts derived from Di, 0, or Bi,o, are known; Bi, O, however dissolves in much molten potash and possibly forms very easily decomposed salts.

Of the remaining oxides, nitrous oxide N, O, nitric oxide NO, nitrogen dioxide NO, and nitrogen tetroxide NOx, are gases; they are all obtainable by reactions between aqueous solutions of nitric acid and various reducing agents; the oxide NO, exists at moderately high temperatures, when this oxide is cooled it becomes very dark reddish black in colour and the vapour density now shews that its molecular composition is expressed by the formula N,OcAll the oxides of nitrogen are acidic; none shews any basic properties.

The haloid compounds are generally obtained by the direct union of their elements; also in many cases by dissolving the trioxides, M,Og, in haloid acid and evaporating. Those elements of the group which form pentachlorides MCls, are P, Nb, Sb, and Ta; the compounds MCl, are produced by heating these elements in excess of chlorine. Trichlorides MCly, are formed by heating arsenic or bismuth in chlorine; vanadium heated in a stream of chlorine forms the tetrachloride VCI, Pentahaloid compounds (MX:) of nitrogen, vanadium, arsenic, didymium, and bismuth, have not yet been obtained ; no trihaloid compound (MX) of tantalum is known; haloid compounds of erbium have not as yet been isolated. Vanadium

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