SYSTEMATIC DETECTION OF ANIONS THROUGH THEIR PARENT ELEMENTS ALCIDES CALDAS and VICENTE GENTIL Escola Nacional d e Quimica, Universidade do Brad, Rio d e Janeiro (Translated by Ralph E. Oesper, University of Cincinnati) attempts have been made to work out a scheme for the separation and detection of anions analogous t o those in use for the analysis of cations, namely by division into groups through successive precipitations. None of these proposals has been adopted universally, largely because of the difficulty of reconciling the conditions permitting the coexistence of the various anions with the conditions requisite to their clean separation. Consequently, many prefer the use of individual tests for each anion. Even though such tests are often satisfactory, they sometimes are difficult to execute, particularly for beginners. Some of these procedures demand much time and material. Futhermore the large number of anions that needs to be taken into account makes the entire scheme lengthy, even though many of the tests will be negative. The analytical procedure obviously would he shortened and simplified if the anions, even without separation, could be classified into groups with respect to their behavior toward certain reagents, provided that the presence or absence of the anions belonging to a particular group could he established by a special test. In view of the availability of tests which permit the grouping of anions from several standpoints, it is thus possible, even though a systematic order is lacking, t o employ at least a methodical procedure to eliminate in advance the possibility of the presence of various anions, and thus considerably reduce the number of confirmatory tests that need to be conducted. VARIOUS
The system of tests suggested here employs reactions now in common use, the investigations of the various anions being limited t o their ability to produce certain readily identifiable substances such as ammonia, hydrogen cyanide, hydrogen sulfide, silver halides, and a few others. The fact that some anions may show their presence in more than one phase of the procedure, depending on the conditions and the intensity of the action of the redox reagent employed, is of no special consequence, since the anions invariably reveal the characteristics of the element from which they originate. The tests based on the formation of insoluble compounds (salts of Ag+, Ba++, Ca++, Zn++, Ni++, etc.) and on the redox behavior are those in common use in the most widely used manuals of qualitative analysis ( I ) , and consequently the present discussion will be limited to those included in the proposed system of tests. Accordingly, among the common elements which yield acid radicals, we select the following arranged in accord with their position in the periodical classificationof the elements:
Excluding oxygen, all of the following anions may be classified within the following groups according to the parent elements :
ELEMENTAL ANALYSIS
We have developed a system of preliminary tests to reduce the detection of the acid constituents to a problem of ultimate analysis, aiming first of all a t the detection of the parent elements of the anions, no matter what their state of combination. Besides permitting a simpler classification of the anions on the basis of their parent elements, this scheme, if combined with other preliminary tests now in wide use (precipitation reactions with cations, reducing or oxidizing behavior, etc.) considerably facilitates the eliminations since, under certain conditions, many anions are mutually excluding. Therefore, the establishment of the presence of certain anions likewise establishes the absence of certain other anions and makes tests for these latter superfluous. The number of tests required to prove the identity of the cations in the sample will consequently be decreased considerably. VOLUME 35, NO. 10, NOVEMBER, 1958
Bromine: Br', BrOL, ~ r 0 ; Iodine: I-, 10-, IOa-, 10,Fluorine: F-.SiF.Phosphorus: HPO$-,.HPo~-, PO4-', PO-', m - , BOsCJ, B,O,Boron: Silicon: SiOa-, S i 4 Carbon: Con-, C2HLV, C204-
De Koninck (3) was the first to propose a method, later developed (1881) by his assistant, H. Slanghen, for the detection of nonmetallic elements regardless of their state of combination. In principle, this procedure was that used by Liebig and Volhard for the ultimate qualitative analysis of organic materials, namely fusion with sodium carbonate plus potassium nitrate. The sample is treated with a solution of caustic alkali, taken to dryness, and the residue then fused with the alkaline oxidizing mixture of carbonate
and nitrate. The cooled mass is extracted with alcohol and filtered. The filtrate may contain the halogens as halides; if present, a t all, sulfur, phosphorus, boron, silicon, carbon will now he in t.he form of salts representing the highest oxidation level: sulfate, phosphate, borate, silicate, carbonate. Arsenic, chromium, manganese emerge as arsenate, chromate, manganate. The nitrogen of ammonium and cyanide compounds is set free. Since nitrate is one of the reagents, nitrite and nitrate must be sought in a separate portion of the material being analyzed. The reduction method by Hempel (9) uses metallic sodium, which is in line with the Lassaigne procedure (4) in which metallic potassium was employed for the ultimate analysis of organic compounds. The reductions are rapidly accomplished but the substitution of metallic magnesium or aluminum is advised hecause of the violence of the reaction with the alkali metals. Sulfur compounds are reduced to sulfide, nitrogenous materials yield cyanide, the halogens appear as halides, and borates and silicates are reduced to boron and silicon. The powerful reducing action of metal hydrides can be employed (5). For example, it has been found (6) that the sulfates, including the alkali and also the insoluble alkaline earth sulfates, are quantitatively transformed to sulfide by heating with calcium hydride: Calcium hydride is rather expensive, but calcium carbide may be used instead. However, the reaction is not quantitative in this case. Roumain, Merland, and Mesnard (7) proposed the use of potassium borohydride in qualitative mineral analysis. If the sample is heated with KBH4, the oxy-acids are reduced as follows: C108- and Br08explosively t o C 1 and Br-; 103-to I-, and SO4to S=; NO3- to Nz. The oxy-acids of phosphorus yield phosphide and phosphine; C03= and GO4= are reduced to carbide; the silicates give an unidentified residue. The compounds of arsenic and antimony produce arsenides and antimonides. The cations of the heavy metals are reduced t o the metal, whereas strongly basic cations retain their positive oxidation state. THE ANALYSIS SCHEME (1) Boil with Alkali
The sample is first treated with an alkaline reagent, as in the usual classic procedure, to avoid the interferences which are encountered in an acid medium. Thus, if an alkaline hydroxide or carbonate is added to a sample containing salts, the ammonia is set free, even in the cold, or more rapidly when warmed. Under such circumstances, the search for the NH4+ cation may be included in the initial phase of the system of the tests for anions. Certain compounds of nitrogen, such as amides, imides, nitrides, cyanamides, and cyanates, though they do not occur very often in the samples presented for analysis, . . .yield ammonia when boiled with a strone. alkali. Other nitrogenous compounds, which yield ammonia under these conditions include cyanide, ferrocyanide,
ferricyanide, thiocyanate. For example, cyanides are gradually decomposed by alkaline hydroxides in concentrated solution on boiling to yield ammonia and formate. Insoluble ferro- and ferricyanides are initially disintegrated and eventually decompose to give the same products as the cyanides. The proposed system also permits the use of the so-called "prepared solution" which is obtained by boiling the sample with sodium carbonate. In this case, however, the test for ammonia is impaired and furthermore it is necessary also to analyze the residue from this treatment, as is usually done (8) because the possible presence of certain compounds of very low solubility does not always permit a satisfactory dissolution or disintegration of the sample. (2)
Reduction by Aluminum Metal
After any ammonia arising from ammonium compounds has been entirely eliminated, the alkaline solution is treated with a metal such as aluminum (9,10,11) to reduce the nitrate and nitrite to ammonia, which can then be detected by the usual tests. Zinc powder or tin foil may be used but their action is slower. Devarda alloy (Cu-50%) Al45%, Zn-5Yo) may he used to advantage since it reacts almost as fast as aluminum but the ebullition is less violent and not so much aluminum is introduced into the solutio~l (12): 3NOsNOz-
+ 8A1° + 5 0 H + 2H20 + 2A1" + OH- + H1O
--
8A10?2A101-
+ 3NH, + NH,
In alkaline solution, ferricyanides are initially reduced to ferrocyanides, hut the reaction is rather complicated and to a great extent depends on the conditions, allowing the formation of various products, including CN-, CNO-, SH3,Cop,etc. Cyanates are not reduced by aluminum in alkaline media (19) but simply decompose because of hydrolysis. Likewise, thiocyanate, when heated strongly with caustic alkali or soda lime in the presence of aluminum, may yield slight amounts of ammouia because of the cyanide formed:
However, the authors have found that the difference in the intensities of these reactions permits a fairly good distinction between NOz- and KO3- and other anions containing nitrogen. To render this part of the procedure more characteristic for the presence of nitrate or nitrite, with avoidance of the decomposition of simple or complex cyanides, the caustic alkali or alkali carbonate may be replaced by Ca(OH)%or by MgO (14) plus metallic zinc: ZnD
+ Ca(0H).
-
ZnO
+ CaO + HI
or mercuric oxide may be added to produce the slightly ionized and stable mercuric cyanide or thiocyanate:
Mercuric oxide (preferably the yellow modification) completely decomposes the simple and complex cyanides (insoluble or not) on heating. Cohalticyanides [CO(CN)~]-~, however, are not decomposed. For example: JOURNAL OF CHEMICAL EDUCATION
When mercuric oxide is used, part of the As(II1) may be oxidized to As(V) which however is readily detected later. Amalgamated aluminum (15) or sodium amalgam (16) may also be used; in addition t o their reducing power, they also have the ability to bind the cyanide compounds. Through their reduction with nascent hydrogen in alkaline medium, it is possible to detect also the arsenites (17) which are readily reducible, yielding arsine (ASH,). This is easily detected with silver nitrate paper, but mercuric chloride paper is a better test. Dauv6 (18) reports that metallic aluminum almost always contains silicon. Under the conditions of the test, this extraneous silicon may yield SiHa, which blackens silver nitrate paper but is without effect on mercuric chloride paper. In concentrated alkali hydroxide solution, hypochlorites are converted on heating to chlorides, liberating oxygen but no chlorine (19): Certain other ions are totally or partially reduced under these same conditions, e.g., C10,-, SzOr, SCN-, but since no volatile products result, these anions do not interfere with the above tests.
(3) Fusion with Sodium formate
After the KH3 and AsH3 have been completely removed, solid sodium formate is added, the solutiou is taken to dryness aud the residue fused. Sodium formate melts at 205'-210°, but if heated abovr 350'-400°, it decomposes (20):
ate and metallic magnesium has been studied by Briickner (24) and Deussen (25). Lidov (26) based a test for the detection of P04c3in rocks on a fusion of the sample with magnesium to produce phosphide, which when moistened with water yields phosphine, readily detected by its odor or by its reaction with paper impregnated with silver nitrate or copper acetate. Wedekind and Diirr (27) studied the reduction of silicates by metallic calcium. However, all of these reductions are usually not complete and some of the original material is left. Accordingly we prefer t o accomplish the reduction by fusion with sodium formate, and to postpone the tests for SO4-, P04c3,SiOa-, R0,-, as well as F-. These latter make up a group that is difficult to reduce. The fusion with the formate-hydroxide mixture, which also contains carbonate derived from the decomposition of the formate, renders the silicates more basic and decomposes the great majority of the insoluble compounds, producing the carbonates, hydroxides or oxides of the respective metals, as mell as the water-soluble salts of the respective acids. (4)
Addition of Acetic Acid
When the residue from the formate fusion is dissolved in water, the arseuide, resulting from the reduction of arsenate, releases arsine which can be detected by silver nitrate or mercuric chloride paper. After removing the arsine completely by hoiling, the suspension is filtered. The filtrate containing the sodium salts is acidified with acetic acid. If hydrogen cyanide and/or hydrogen sulfide are evolved they indicate respectively the possible presence of CN-, [Fe(CN)6]-4. [Fe(CN)6]-3,andSCN-, and of S-, SOa-. St04-, Sz03=. The simultaneous evolution of HCN and H2S may be due also to the presence of CNS-. The two gases may also be obtained because of the presence of bot,h C S - and S203=, which may react to give ChTSSrO,-
or a mixture of formate and alkali (21) when heated reacts: NaCOOH
+ NaOH
-
NaC03
+ H2
Under these conditions, SCN-, [Fe(CN),]-', [Fe(CN)e]-3 are transformed into CN- with possibly n little ammonia being formed; likewise, SCN-, S203=, SO3=, S,06- are converted into S- along with some SO4-. The oxy-halogenated ions yield the respective halide ions, aud the arsenates (22) are reduced with liberation of arsine, which may he detected by the usual methods. Some elementary arsenic also results; it sublimes and forms a mirror on the cold areas of the reaction vessel. Small amounts of hydrogen sulfide and hydrogen cyanide may be released during the fusion with sodium formate. If a reducing agent more powerful than sodium formate is used, SOs-, SOp-, SO3=, and B02will also be affected. Thus if metallic magnesium or calcium is added-and the alkaline residue then fused, there will br considerable reduction of these ions. According to Castellana (28) the fusion mass can produce nascent potassium, i.e., a powerful reductant. The reduction of sulfates by fusion with sodium carbonV O L U M E 35, NO. 10.NOVEMBER, 1958
+ CN-
-
SO1-
+ CNS
If it is desirable to apply a test of a general character (28) which takes in any acid containing nitrogeu as
mell as all nitrogenous materials, use may be made of the production of nitrous oxides xvhen any of these substances is heated with ignited manganese dioxide (29). The vapors call be tested with paper impregnated with Griess reagent or the Saltzmaun reagent (SO). The presence of sulfide, thiosulfate, and thiocyanate can be specifically confirmed by observing the catalytic effecton the iodine-azide reaction (5'1). (5) Oxidation with HNOI
After the acids HCN and/or HzShave been identified, the mixture is brought to dryness and the residue is taken up in dilute nitric acid and filtered. This treatment will oxidize all products arising from the foregoing reduction of the sulfur and phosphorus acids, transforming them into sulfate and phosphate, respectively. The organic residues, which apparently account for the darkened precipitate when phosphate is precipitated by silver (St), are destroyed by this oxidizing procedure. The presence of silica in the resulting residue can he validated only if the preceding operations have been conduct,ed in a nickel crucible.
+
(6) Addition of Ba(N0s)r Solution
The acidified filtrate is treated with barium nitrate solution. This removes any sulfate ions which may have been present from the start either legitimately or as impurity. The sulfate may also have arisen from sulfite or in a lesser degree from thiosulfate as a result of oxidation: 2S20s-
+ 301 (air)
-
250,-
+ 250%
or from CNS-, Sp08=,SOa=,etc., which can give rise to SO4- through reactions such as.
paper impregnated with a solution of MnSO, Hn02. If am&&a, is kvdved, proving the presence of ammonium salts, the pitper will turn brown. This is due t o the formation of M ~ O reE sultine from the oxidation of Mn(I1) ~eroxide in the , ,bv.hvdroeen " * resulting alkaline medium. All of the ammonia coming from the ammonium salts or derived from the hydrolysis of any nitrogenous compounds must be completely removed before proceeding t o test for nitrate and nitrite. This removal may be accomplished by continuing the heating with sodium hydroxide or if necessary by evaporating t h e solution almost to dryness and then taking the residue up in water. (2) If the volume of the solution has been considerably diminished, a little more water should be added. About 20 mg. of aluminum powder (or Devsrda's alloy) is introduced and the suspension gently heated. N O z and NO8- are reduced to amH20r monia. and the latter is verified by means of MnSOd paper exposed t o the vapors. Likewise, AsOs- is reduced t o a c sine whose presence can be disclosed by the yellow or brown stain appezwing after a few minutes if paper impregnated with a 3% solution of HgCh is placed a t the mouth of the test tube or crucible. (3) About 0.5 g. of solid sodium formate is then added, the mixture taken t o dryness, fused, and heated for 3-5 minutes a t 400'-500"; During the fusion, HgC1,-paper should be held close to the mouth of the vessel t o detect any arsine produced by the reduction of arsenate (AstO4-9: Elementary arsenic may he liberated during the fusion; i t rnll sublime and produce a mirror on the cold part of the test tube or crucible. Slight quantities of HCN and H B may be released. Since the latter interferes with the test for arsenic, it may be trapped by a plug of cotton soaked with saturated lead acetate solution and placed on top of the test tube. The mixture is allowed t o cool and the residue is then taken up in water. The HgCL-paper should be kept over the mouth of the vessel t o reved any arsine farmed by the action of water on arsenide. The solution is then warmed gently to expel the arsine completely, and then filtered or centrifuged. (4) The clew alkaline filtrate or centrifugate is made acid to litmus paper with fi N acetic acid. The solution is warmed and the resulting vapors tested with lead acetate paper t,o reveal H?S. The vapors are also tested n.ith (NH&S-paper, t o which has been added a 1%solution of FeCL t o detect HCS. If no H9S is found, the HCN may be detected by means of copper acetate bensidine acetate reagent. A positive response to the test for H2S indicates the possible presence of S-, CNS-, Sz04-, Sz03-. Similarly the presence of HCN signals the possible p~esence of CN-, CNS-, [Fe(CN)eI-3, [Fe(CN)81-4. (5) The solution is now treated by evaporation to dryness, the residue is taken up in 1 ml. of 2 N HEOX,warmed gentlv, and filtered. If it is desired to test far silicate, the residue is fused in a platinum loop with Na2C0a. (In this case the previous operations must have been conducted in a nickel crucible.) The material remaining in thc loop is tested with a warm solution of ammonium malgbdste in nitric acid. A yellon color indicates silicate. If s. drop of the solution is then placed on filter paper and treated with 1-2 drops of a solution of benzidine in acetic aeid, and then exposed t o NH, vapors, a blue color appears if silica is present. I n case a, test for silicate is not t o be performed, the acid-insoluble residue is thrown away. (6) The acidic filtrate is treated with 1 N Ba(NO& solution added drop by drop. Since Ba(NO& is only slightly soluble in a solution containing a high concentration of nitrate ions, the precipitate may not be BaSO, but Ba(NO&. However, the latter is soluble in hot water. The formation of a BaSO, precipitate indicates the possible presence of SOj; SO,-, &Oa- and of sulfur-bearing anions in general. The suspension is allowed t o stand for 5 minutes and then filtered. (7) The silver halida (AgCl, AgBr, AgI) are precipitated by adding 1 N AgNOZsolution. The suspension is filtered or centrifuged and the usual methods me applied to learn the identity of the halide ions present. (8) The filtrate iis made just neutral t o litmus by adding drops of 3 N NaOH. Excess alkali must be avoided since hydrated silver oxide dissolves but slowly. The neutral solution is then treated with 0.5 ml. of 3 N acetic aeid and more (O.&1 ml.) 1 N AgNOl if necessary, and heated gently to 80'-90'. A yellow precipitate (AgaP04)indicates the presence of phosphorus-hearing anions. The identity of the precipitate is established by dissolving. i t in 6 N HNOs and placing 1 drop of the solution on filter paper. The spot is treated with 1 drop of ammonium
-
+
In any event, the presence of sulfate ions indicates the presence of anions derived from sulfur. At this stage the solution will therefore contain, besides the halides including F-, the anions coming from acid radicals which are decomposed or reduced with difficulty under the ordinary conditions, such as P 0 4 i 3and BOz-. (7, 8) Precipitations with Silver Nitrate Solution
The addition of silver ions to an acidified solution will precipitate the silver halides (except fluoride) and indicate the presence of the corresponding halide ions. This precipitate is subjected to the usual procedure to verify the presence of ch'oride, bromide, iodide. Taken in conjunction with the results of the other preliminary tests, the findings are used later to establish the presence of the respective anions. The solution is then buffered at approximately pH = 5.5 by adding sodium acetate-acetic acid solution, and the phosphate is precipitated as silver phosphate. (9) Tests for Fluoride and Borate
The neutral or faintly ammoniacal solution may be tested for fluoride by precipitation of CaF2. Finally, the test for borate is conducted on the last filtrate. Separate portions of the solution may also be taken for individual tests for PO4-$, F-, and BOz-, and without any separations, by employing separate parts of the filtrate obtained after precipitating the silver halides. Since the [SiF6]= ion is destroyed by bases, it consequently is decomposed on treatment with caustic alkali solution or when fused with sodium carbonate: Under these circumstances, the concurrent presence of Si03- and F- ions may indicate the presence of [SiF6]- in the original sample, a possibility that must be explored with a separate portion of the unknown. The usual procedures are used t o determine the presence of anions containing carbon, namely carbonate, acetate, oxalate, which are customarily included in inorganic qualitative analysis. Individual tests are employed for these. WORKING DIRECTIONS (1) A small test tube is used, or a nickel crucible if SiOss iona need t o be considered. About 2&30 mg. of the solid, or a. volume of the solution containing a comparable weight of the dissalved solid, is treated with 1-2 ml. of 3 N sodium hydroxide and the mixture or suspension is brought to a gentle boil. The mouth of the test tube or crucible is covered with a disc of filter
548
JOURNAL OF CHEMICAL EDUCATION
malybdate-tartaric acid solution (5g. ammonium molybdate and 15 g. tartaric acid dissolved in 100 ml. of 6 N nitric acid.) The paper is warmed over an ashestos-covered wire gauze and then treated with 1 drop of benzidine solution (0.005g. bensidine base dissolved in 10 ml. concentrated acetic acid and then diluted to 100 ml.). If phosphate is present, the spot turns blue on exposure to smmonia vapors. (9) The filtrate is made neutral or faintly basic by adding drops of 6 N ammonium hydroxide. Then a 2 N solution of calcium acetate is added until all of the CaF* is precipitated. The SUEpension is brought to boiling, allowed to stand 5 minutes, and filtered. The precipitate is calcined, digested with acetic acid, diluted, filtered, and the residue is treated with 4 or 5 drops of the following reagent: 0.05 g. of zirconium nitrate in 50 ml. of water plus 10 ml. of concentratedHCI; the solution is then mixed with a solution of 0.05 g. sodium alizarin sulfonate in 50 ml. of water. This reagent dissolves calcium fluoride with the pr+ duction of [ZrF6]- ions and free alizarin sulfonic arid. A yellow color appears if fluoride is present. (10) The filtrate is tested for borate ions. A few drops of concentrated H.S04 are added to the filtrate in a porcelain dish and the liquid taken almost to dryness. A little methyl alcohol is added and the vapors set on fire. Methyl borate, (CH&B08, burns with t~ green flame. Alternatively, 2 or 3 drops of a 0.01% solution of quinalizarin (1,2,5,&tetrahydroxyanthraquinone)in concentrated HlS04 are added to the filtrate. If borate is present, the violet color changes to blue. The following schematic outline summarizes these mccessive steps: ( t = gas or volatile products; 1 = precipitate or insoluble residue) Procedure: Observation: Infetenee: 1. Treat sample with NHa t NHlf NaOH and bail. 2. Add Al and bail. NHs t NOS-. NO,
~&'t
3. Fuse with NaOCH. H,As t Add water and boil. 4. Filter and add HAc HCN t to the filtrate. HIS t 5. Evaporate to dry- SiOt l ness and add HNO. 6. Add Ba(NO&.
7. Add AgNO1.
8. Neutralize with NaOH; add HCvHxO.and 9. Neutralise with NH,OH; add C~(GHBOJ.. 10. Evaporate to dryness add H2S04 and CH.OH. Ignite the vapors.
CaFz I
A~O~: As04i8 CN-, Fe(CN)sc4, Fe(CN).-8, CNSS-, S205-, CNSSi0,-, SiF.SOz-, SO,-, SDa-, SnOa,CNSc1-, C10-, C101-, ClOa-, cmBr-, BrO-, BrOlI-, IO-, 103-, 10,H1P02-, HPOz-, PO~P, iPO.-L F-, SiFs-
instances, when all of these anions belong to different test groups, the number of other tests that can be omitted is still considerable. After these preliminary group tests have been completed, a brief study of their revelations combined with the results of the other customary preliminary tests such as those for volatile oxidizing or reducing acids will restrict even more the number of anions that may he present. A few confirmatory tests will then usually suffice. The net result is that the search for anions is not only accomplished in less time but with more reliability. Finally, since the scheme outlined here is based on the chemical nature of the parent elements, the effects of the reciprocal interferences between the anions is eliminated. ACKNOWLEDGMENT
The authors are indebted to Professor Fritz Feigl for his many helpful suggestions. LITERATURE CITED (I) NOYES,A. A., AND E. H. SWIFT,"Qualitative Chemical Analysis of Inorganic Substances," 10th ed., The hlacmillan Co., New York, 1942, pp. 314-19. L. L., "Trait6 de Chemie Analytique Mineral6 (2) DE KONINCK, Qualitative et Quantitative," Val. 4,3rd ed., Li~ge,1918, p. 933. HEMPEL,W., Z. anoq. Chem., 16,22 (1898). LAS~MGNE, J. L., Compt. rend., 16, 387 (1843). VILA,L. A,, Compl. l a d . , 179, 1163 (1924). CALDWELL, W.E.,A N D F. C. KRAUSKOFP, J. Am. Chem. Soc., 51, 2936 (1929). . ROUMAIN, P., R. MERLAND A N D P. MESNARD, Bull. sac. chim. Prance, 10,1298-1304 (1954). NOYES.A. A,. AND E. H. SWIFT.on. cil.. DD.375-82. SC~~L= F .E. ',~ i n g l w ~ s o l ~ l e c h . '1j6.2,,'46, 287 (1861). DE KONLNCK, L. L., Z . anal. Chem., 26, 26 (1887). SEYEWETZ, A,, Bull. soe. chim. France, 141, 45, 463 (1929); Z . anal. Chem., 87, 57 (1932). DEVARDA, A,, Chem. Zlg., 16, 1952 (1892);Z.anal. Chem., 33, 113 (1894). DE KONINCIL, L. L. Trait6 de Chemie Analytique Minerale Qualitative et Quantitative," Vol. 4, 3rd ed., Liege, 1918, p. 216. DAVID~ON, J., A N D A. KRASNITZ, Ind. Eng. Chem., Anal. Ed., 6, 315 (1934). Pozzr-Escm, E., Compt. r e d . , 149, 445 (1909). BLUNT,T. P., Chem. News, 18,179 (1868). FLEITMANN, TH., Ann., 77, 126 (1851). 131, 10, 321-21 . . DAUVS,M.,Ann. chim. anal. el. ehim.appl., . (1928). (19) WINTELER, F., Z.angew. Chem., 33, 778 (1902). (20) DUMAS,J. B., AND J. S. STAS,Ann., 35, 138 (1840). Z. Electroch,em., 10,706 (1904). (21) HABER,F., AND E. BRUNER, A. C., Ber., 43,2264 (1910); Comp. rend., 150, (22) VOURNASOS, 464 (1910). V.,Gau. ehim. ital., 34, 2, 357 (1904). (23) CASTELLANA, C., Monatsh. Chem., 26, 625 (1905). (24) BR~~CKNER, E.,Z.anal. Chem., 46,320 (1907). (25) DEUSSEN, (26) LIDO^, A. P., J . Russ. Phys. Chern. Soe., 40, 817 (1908). E., AND L. DOER, Z. angezn. Chem., 25, 1265 (27) WEDEKIND, (1912). (28) FEIGL,F., Anal. Chcm., 30, 1148 (1958). AND J. H. REEDY, (29) PPEISING,SIBTERM.J., 0 F. SLONEK, Ind. Eng. Chem., Anal. Ed., 14, 875 (1942). (30) FEIGL, F., "Spot Tests," Vol. 1, Inorganic Applications, 4th ed., Elsevier, 1954, p. 302. See also, SALTMAN, B. E.. Anal. Chem.. 26. 1949 (1954). . . (31) FEIGL,F., ibid., p. 280. ' (32) NOYES,A. A., AND E. H. SWIFT,op. cit., p. 355 et seq ~
B08(CH& t BO1-, Boa?, B~OI-
SUMMARY
Each test in this scheme establishes immediately the absence or presence of one or more of the materials included in the compilation. Hence if a negative response is obtained, all of the usual procedures for detecting these particular ions may be omitted. In this sense these group tests are used to establish the absence of particular anions rather than their presence. Most samples contain not more than three or four anions. Accordingly, even in the most unfavorable
VOLUME 35, NO. 10, NOVEMBER, 1958
