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Examination of the Solution.

Fused some of the powder with fusion mixture on platinumfoil: boiled the cold mass with water, filtered.

Filtrate, made acid with HCl and added BaCl2, a white precipitate, which did not disappear on boiling the liquid :— Presence of SO4.

The residue on the filter was well washed with boiling water, and boiling dilute HCl poured upon it, it dissolved completely:

Absence of To a portion added strong H2S-water and heated:

Group I.

No precipi- To another portion added AmCl, then AmHO in excess, then Am2S, and boiled:

tate.

Absence of
Group II.

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SECTION VI.

FULL ANALYTICAL COURSE AND TABLES.

AFTER having tried the reactions for the members of the analytical groups and learnt for each group how to detect its members occurring singly or two or more together, solutions containing a single metal belonging to any of the groups, or members of two or more of these groups mixed, will readily be analysed.

370. It is necessary first to separate the metals present into groups by adding the group-reagents successively in such an order that each precipitates its own group only, leaving in solution the members of all other groups which may be present. This is effected by adding the group-reagents in the order directed in the General Table (419); refer to this and to the Group Table on pp. 168, 169. HCl, which is the first reagent added, precipitates only Group I. leaving Groups II., III., IV., and V. in solution; hence if a precipitate is obtained on adding excess of HCl, after filtering it off any member or members of Group I. present will be obtained upon the filter, whilst the members of all other groups remain in the filtrate. On passing HS into the heated filtrate,* members of Group II. alone will be precipitated and may be filtered off; the filtrate,* after removal of HS and oxidation of any Fe present by boiling with HNO3, may be mixed with AmCl and excess of AmHO; the AmHO will precipitate any members of Group III. A., Group III. B. and Mg remaining dissolved by the AmCl; the addition of Am,S to the filtrate* will separate Group III. B. as sulphides. Group IV. is precipitated from

*Or solution, supposing no precipitate to have been obtained, and filtration therefore to have been unnecessary.

the filtrate* by the last group-reagent Am,CO,, and the filtrate is examined for Group V., the members of which not being precipitated by any group-reagent will now remain in solution if they were originally present.

Since each group must be entirely precipitated by its own group reagent it is necessary, if any precipitate is formed, to add each group-reagent in "excess" before proceeding to add the next: unless the presence of the reagent in excess is ascertained before proceeding, much confusion may be caused.

371. Addition of Reagents in Excess.-The most general method for ascertaining the presence of a reagent in excess is to add a few drops more of the reagent to the clear liquid obtained either by letting the precipitate settle or by filtering off a small quantity of it; if any further precipitate is formed the filtered portion must be returned, more of the reagent must be added, and the clear liquid again tried with a few additional drops of the reagent, this process being repeated until no further precipitate is caused.

In certain cases this method of proceeding is rendered unnecessary, the excess of a reagent being detectable by its smell after thoroughly mixing up the solution and blowing out the air above it; this is the case for example with H2S and AmHO. In other cases the excess is seen by the colour of the filtrate, as with yellow Am2S for example.

372. Since certain organic substances hinder or prevent the precipitation of the members of Group III. a. by AmHO, it is necessary, if the preliminary examination has shown the presence of organic matter, to destroy it by evaporation and ignition before proceeding to precipitate Groups III, and IV.: evaporation to dryness and gentle ignition are also necessary to separate SiO2, which if remaining in solution might be mistaken for AlHo. But if it is known that neither organic substances nor SiO2 are present, a considerable saving of time may be effected by boiling the HS filtrate until it no longer

* Or solution, supposing no precipitate to have been obtained, and filtration therefore to have been unnecessary.

smells of HS, then continuing to boil for several minutes after adding a few drops of strong HNO,; this process may replace the evaporation to dryness and ignition.

373. The ordinary method of analysis drawn out in the General Table and in the Tables for examination of the Group precipitates will present little difficulty if the directions therein given are strictly complied with. Table III. c. will perhaps be found a little more difficult, and should not be attempted until some proficiency has been obtained by practice on the other Group Tables. Table III. D., which must be employed under conditions fully explained in (460), should not be used until considerable proficiency has been attained.

374. It will be seen that the full course of analysis is arranged so as not only to prove what is present, but also that all else is absent: this, except in special cases, is the object in view.

The process of analysis is much hastened by using separate portions of the solution instead of carrying on the examination throughout with one part of the solution: the plan in the General Table is however preferable, since it gives at once a notion of the relative quantities of the different substances present.

For an example of how to write out the results see pars. (488-493); it will be seen that the form adopted is that of the Analytical Tables.

PRELIMINARY EXAMINATION OF SOLID SUBSTANCES.

375. Before proceeding to employ the full course of analysis for substances of complex composition, the student will do well to examine a few solid substances for metals and acid-radicles by the tables given in paragraphs 387–418.* For the full account of how to try these tests for any particular substance the student must refer back to the preceding reactions in Section IV.

* For examples of substances to be analysed by the Preliminary Examinations, see paragraph 538.

The results of these analyses are entered in the form of the Table as shown in the examples in paragraphs (488) and (489). The entries must be made during the progress of analysis.

376. Preliminary Examination for Metals.-A little study of this Table (387 et seq.) will show that it contains three main tests marked Exps. I., II., and III.; these stand in the first column: in the second column are placed the results which may be noticed on trying these experiments; the student should glance through these so as to be forewarned of what he has to look for. The main classification of the results which may be observed is indicated by large-type letters, the subsidiary divisions are marked by small numbers, and the individual results are simply placed in succession in a vertical column. Occasionally an observation is made which it is advisable to confirm by an additional experiment: this “ confirmatory" test is then entered in the first column, just below the observation to be confirmed, and is marked "confirm"." to distinguish it from the main experiment, its results are placed beside it in the second column: the student must understand that any one or more of the results noted in the second column may be looked for.

A few salts and mixtures such as those mentioned in (538) should be subjected to a careful preliminary examination by the student, and the results obtained carefully entered.

377. Preliminary Examination for Acid-radicles.-This Table (410-418) exactly resembles in arrangement the Table for metals which precedes it, and no explanation is therefore necessary. The student should examine by it some solid substances (538) for acid-radicles only.

378. A few solid substances may now be tested for both metals and acid-radicles by the two Preliminary Tables.

SIMPLE SUBSTANCES, DETECTION OF ACID-RADICLES AND METALS BY PRELIMINARY TESTS AND BY EXAMINATION OF THE SOLUTION.

379. After having become familiar with the preliminary examination of solid substances the student may analyse some

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