Actual analysis for the detection of the acid constituent.

To the solution add excess of HNO3.

A dense precipitate

S

or U.

If the plan described in the introductory

remarks has been followed, the absence of a precipitate here might arise from the previous separation of the acid by the addition of dilute HNO3.

a gelatinous presence of AgNO,.

A preci- To the sopitate in-lution add dicates the HNO, and

dicates the

presence of

dicates the presence of

Cfy

Csy

Bz

C204

BOO2

A precipitate indi

A or Cfdy.

Sio,

cates the

or Qt.

TABLE FOR GROUP I.

The precipitate may be BaF, Ba,Si, F, BaŌ, Ba T, Ba,Ci, Ba,PO, BaBoO2, or BaSiO2.

To the solution add dilute HCl, and then divide the liquid into two parts.

TABLE FOR GROUP II.

The precipitate may be AgCl, AgBr, AgI, AgCy, AgCsy, Ag2 Cfy, or Ag, Cfdy. Add NH,HO, and warm.

* These reds may be distinguished by adding HgCl; when the colour of Fe,Csy, is discharged, and that of FeA, remains.

CHAPTER III.

ANALYSIS OF MIXED SALTS.

In the recognition of the various basic and acid-radicals which may be present in a mixture of salts, the plans described in the following Tables are to be adopted, with, however, such modifications as the preliminary examinations may suggest. To the methods of preliminary examination already given (see pp. 391, 404) recourse must again be had; indeed, the indications which they afford are often of extreme value in the analysis of complicated mixtures. The methods for preparing the solution of the substance to be analysed will be the same as those already described. (See pp. 392, 408.).

A few words may here be introduced concerning those combinations and mixtures of basic radicals with one another, known as alloys and amalgams. When once in solution, the manner of recognizing their constituents is identical with that adopted in the case of salts; but nitric acid, moderately concentrated, which is usually employed as the solvent for alloys, leaves many metals unacted upon and undissolved (e. g. platinum, gold, &c.), which require further treatment with hydrochloric or nitrohydrochloric acid. Nitric acid, moreover, partly separates tin and antimony in the form of insoluble compounds, which must then be treated according to the plan described on p. 394.

Throughout the Tables of the present and preceding chapter, the more common radicals are indicated by a conspicuous type. For the detection, &c. of the acid-radicals contained in a mixture of salts, the Tables already given may be employed (see pp. 413, 414); from these Tables, the rarer organic radicals, the reactions of which have been detailed in Chapter VII., are for the most part omitted, since they seldom occur together in the course of analysis, and generally require the employment of very special methods of separation. For these methods, reference must be made either to Chapter VII. or to a comprehensive treatise on Organic Chemistry.

The preliminary examination of the mixture of salts having been accomplished, and its results recorded, the student will then proceed to the actual analysis.

GENERAL TABLE FOR THE

If HCl has been used for the solution of the substance, and no precipitate be assumed to be absent; but if the substance has been dissolved in water addition as long as any precipitate is produced: when the precipitate ceases, ride of Bi or Sb, or any HSiO2, which may have been thrown down. Agitate

The filtrate is first freed from HNO, by one or two separate Pt and the mass of the rarer allied metals, given in Table for Group II. If extremely acid, it suspected to contain As in the form of arsenic comof the latter is expelled*, when a rapid stream of H, S pitation of Pb, As, and Mo, it is well to warm the fltime, with H, S. A blue colour on the first passage of precipitate may be only S, due to the oxidizing action ever, a mass of S might easily mask a small but imporsuffered to pass unexamined. Collect and wash the

The precipitate may contain

H2S and
HU

may be here precipit

Cu S

As, S3

ated, since they are but

CdS

As, S

slightly soluble in

Pd S

Mo2 St

water or acids.

Sn S

Examine according to Table
for GROUP II.

TABLE FOR THE ANALYSIS OF GROUP I.

The precipitates produced by the addition of HCl, and remaining undissolved in excess of that reagent, may contain

PbCl, AgCl, and Hg, Cl; the anhydride W2O3; and the acids HSbO3, H4 Sb2 07, HBOO2, HBZ, H2 S, and H2 U.

Boil the precipitate with several fresh portions of water, and wash it, when on the filter, with hot water.

The solution

may contain

PbCl, HBOO2, HBe

and H, S.

The residue may contain

AgCl and Hg, Cl; W203; HSbO3, H4 Sb2 O7, and H2 Ū.
Warm with solution of KHO, filter and wash.

The solution

may contain

Add dilute

H2SO1; a

KWO2
KSbO3

white precipi

K2 H2 Sbg O7

and

tate indicates

K2 U.

the presence of The W may be

Pb.

The acids will be found in the

analysis for acid-radical.

detected by the blowpipe reactions; the Sb by the H3 Sb series of experiments.

EXAMINATION FOR BASIC RADICALS.

either immediate or on cooling has been the result, the first group may or in HNO, or H, SO4, add a few drops of concentrated HCl, and repeat the add yet a few drops more of the concentrated acid, to redissolve any oxychlountil the solution is clear, and then filter.

evaporations on a water-bath with HC1; it is then treated with NH, Cl, to and subsequently with HCO to precipitate Au, according to the details should then be partially neutralized with Na, CO, still keeping it acid; and if pounds, it must be saturated with SO2 gas: it is then warmed until all excess gas is passed through it for at least half an hour. To ensure the perfect precitrate from the first HS precipitate, and to saturate it a second, and even a third HS should lead the student to look for Mo. A white or very pale yellow of unexpelled HNO3, of HCrO2, or of ferric salts upon the H, S. Since, howtant quantity of Sb, S, or As, S, or other bodies, no such precipitate must be precipitate completely.

3

3

fine blue colour, special search for Ru should be made in the Pt precipitate Mo may be looked for again in the following group. The filtrate should be now 100° C. with HNO,; this process should be repeated, and the residue finally just again evaporated to perfect dryness: absolute desiccation ensures the complete Si, O.; it would otherwise be mistaken for Al, H, O. If organic matter is prebe more highly heated, in order that the detection of Al, Cr, Fe, Mn, &c. may It is well to burn organic bodies off entirely, by igniting the residue strongly in danger is, that by exposing sesquioxides to so high a temperature they are rena compromise is therefore frequently effected by heating until merely a carwhich is boiled repeatedly with HCI, and the solution filtered. It would be residue white, to ascertain whether Si, O, is present.

3

To the HCl solution add some quantity of NH, Cl; then almost neutralize with NH, HO; place in a flask, and add (NH4)2S until no more precipitate is produced: warm gently, allow to rest for some time in the corked flask, and filter, washing with water slightly impregnated with (NH1), S.

If the filtrate is brown, the presence of Ni may be inferred. First acidify with HA; warm, filter, and add the new precipitate to the one previously produced. The filtrate should be evaporated to expel excess of (NH), S, and any precipitate of S resulting from its decomposition ascertained to be only S by its entire volatility. Solution of (NH), CO, is then added until the precipitation ceases; the liquid warmed (not boiled, lest the precipitate should redissolve in the NHCl) and filtered.

* Certain sulphates, as those of Ba, Sr, and Ca, may be precipitated here, the SO2 being eonverted into H2 SO. If insoluble in acids, such precipitate must be examined by fusion.

Mo is not perfectly precipitated unless H2S is passed into its alkaline solution, which is afterwards acidified.

T 5