April, 19501 THIOPHOSPHATE, E605, PARATHION 191 Spot-tests for the Identification of Alloying Elements in Copper-Base Alloys* BY B. S. EVANS AND D. G. HIGGS SYNoPSIS-’rhe tests described in this paper constitute a complete qualitative scheme for the non-destructive examination of copper and its alloys. The elements that can be detected are: manganese, zinc, tin, iron, lead, silicon, nickel, aluminium, beryllium, arsenic, cadmium, cobalt, chromium and phosphorus. The tests consist of addition of drops of reagent to the cleaned metal surface, followed by further reagent to produce a coloured precipitate characteristic of the metal sought, or removal of the drop of solution from the metal surface on to a filter-paper or spot-plate, for production of a specific reaction. The aim has been to reduce to a minimum the number of operations and the manipulative skill required so that the tests can be applied with satisfactory results by persons of limited chemical knowledge.THE tests to be described in this paper constitute the last of a series of researches dealing with the detection of alloying elements in various types of alloys. Papers already published for the spot-testing of alloys include, “Steels,”l “Aluminium and Magnesium-base Alloys,”Z “Zinc-base alloy^,"^ “Lead-base Alloys”4 and “Tin-base Alloys. J ’ s As far as possible these tests have been employed in the present series. * Communication from the Armament Research Establishment (formerly Research Department, Woolwich),192 EVANS AND HIGGS: SPOT-TESTS FOR THE IDENTIFICATION OF Apparatus-It has not been found necessary to introduce any new apparatus and, since adequate description has already been given in previous papers, no further words need be added here.[Vol. 75 THE TESTS- Copper offers a very wide range of alloying elements, and tests have been evolved for the following elements : manganese, zinc, tin, iron, lead, silicon, nickel, aluminium, beryllium, arsenic, cadmium, cobalt, chromium and phosphorus. The usual alloying quantities of selenium, tellurium and silver are so small that no definite tests have been forthcoming; hence these elements are not included in the present work. The test to be described for silicon is based on dye-absorption by the hydrated silica; the preliminary results were so perplexing that an investigation was carried out, ‘by one of us, to determine the exact condition under which absorption occurred.The findings of this investigation have been adapted to the test for silicon, but a more detailed account will be published at some future date by the author concerned. It has been found possible to test for aluminium and beryllium at the same time in such a way that both elements can be detected by their distinctive markings. After a single-wash treatment, to bleach the aluminium completely, the beryllium can be plainly seen. Compositions of the trial alloys are given in the Appendix, pp. 199-200, and the numbers at the end of each test refer to that Appendix. It is very important to the success of the tests that the surface of the specimen should be thoroughly cleaned with a fine emery paper, Grade IG or similar, immediately before the reagents are applied. (I) MANGANESE Reagents-(a) Diluted nitric acid (sp.gr.1.20). Method-Place 3 drops of (a) on the cleaned surface and leave for 5 minutes, add a further 2 drops and transfer, with the aid of a capillary tube, to the well of a white spot-plate. Drop into the solution a little of (b), stir and leave for the full development of colour. In presence of more than 15 per cent. of manganese, rapid decomposition into the hydrated oxide occurs; between 0.4 per cent. and 15 per cent. of manganese is indicated by varying intensities of purple permanganic acid, and 0.1 per cent. is visible as a light purplish coloration of the drop. Tried on: Samples Nos. 1, 2, 3, 4, 5, 6, 8, 9, 10, 11, 12*-Manganese present; all results Nos, 13, 14, 15, 16, 17, M, 19, 20, 21, 22-Manganese absent and all Our aim, as before, has been to make every test specific and unambiguous. (b) Sodium bismuthate (solid).In absence of manganese the drop remains blue. positive. results negative. (11) ZINC Reagents-(a) Concentrated nitric acid (sp.gr. 1-42). (bj Distilled water. (c) Sodium hydroxide solution (20 per cent.). (d) Diphenylcarbazone (1 -5 per cent. solution in alcohol). (e) Ammonium nitrate solution (20 per cent.). Method-Place 1 drop of (a) on the cleaned surface and leave until the vigorous attack has subsided, then wash off with a fine jet of distilled water on to a clean watch-glass. Add 3 drops of (c) and stir thoroughly; the mixture should now react alkaline to litmus paper.Filter off the cupric hydroxide precipitate through a glass-tube filter, collecting the filtrate on a 12.5-cm. Whatman No. 541 filter-paper, supported on the open mouth of a beaker. Wash the watch-glass with 3 drops of (b) and pour through the filter-tube. Remove the tube, place the filter-paper on a clean tile and cover with a second filter-paper thoroughly soaked with (e); ensure complete contact at all points by rolling with a glass rod. After 20 to 30 seconds, strip off the ammonium nitrate paper, replace t.he test paper on its beaker and leave exposed to air for 5 to 10 minutes. At the end of this period the filter-paper ought to be free from all “fixed” alkali and substantially free from ammonia. Add 4 drops of (a), followed when * First discovered by spot-tests and subsequently confirmed by chemical analysis.April, 19501 ALLOYING ELEMENTS I N COPPER-BASE ALLOYS 193 spreading is complete by a further 4 drops.Again transfer to the tile and re-treat with a filter-paper well soaked in (e); this time manipulate the glass rod from the outer edges of the coloured spot to prevent undue spreading of the colours and to ensure an ample excess of ammonium nitrate all over the coloured patch. Remove the upper paper and suspend the test-paper to dry. When more than 3 per cent. of zinc is present, the first addition of reagent (d) to the slightly ammoiiiacal test-paper results in a deep violet patch, whilst 1 per cent. of zinc gives a violet ring just inside the outer edge of the reagent patch, the remainder being orange-red in colour.In absence of zinc, or where the zinc content is low, the coloured ring is usually reddish-brown. Final treatment with (e) tends to accentuate the zinc colour whilst changing the reagent - ammonium nitrate colour from reddish-brown to brown. When dry, all papers not containing zinc show a peach-colouredcentre with a brownish outer ring; 0.5 to 2.0 per cent. of zinc gives a peach centre more or less completely flecked with violet and a rather broad violet ring, or band, at the outer edge. Above 3 per cent. of zinc gives a deep violet colour to the whole reagent patch. If the zinc content is less than 1 per cent., the above test should be replaced by the following. Treat a 12.5-cm. Whatman No. 541 filter-paper with 2 or 3 ml.of an equal mixture of (d) and (e) and leave to dry; the paper should then appear very pale mauve with a yellow outer band. Filter the alkaline mixture, obtained as described above, on to this pre-treated paper. Remove the tube, wash the paper, from the centre, with 2 drops and then with 3 drops of (e), and finally treat with a disc of filter-paper moistened with (e) and hang up to dry. The zinc should now appear as a broadish irregular purple-violet band about 2 to 3 inches in diameter. Tried on: Samples Nos. 17, 23, 24, 25, 26, 27, 21, 28, 16, 22, 1, 29, 30, 31, 32, 33, 34, Nos. 13, 14, 4, 37, 40, 41, 19, 45, 12, 15, 5, 42, 43-Zinc absent and 35, 36-Zinc present ; all results positive. all results negative. (111) TIN Reagents-(a) Concentrated nitric acid (sp.gr.1-42}, 1 vol. ; tartaric acid solution (50 per cent.), 1 vol. (b) Potassium iodide solution (20 per cent.). (c) Concentrated hydrochloric acid (sp.gr. 1*16), 1 vol. ; potassium cobalti- cyanide solution (10 per cent.), 5 vols. (d) Toluene-3 : 4-dithiol* solution in acetone (0.5 per cent.), 2 vols.; thio- glycollic acid solution in acetone (0.5 per cent.), 1 vol. Method-Attack the surface of the cleaned specimen with 1 drop of (a) and leave to react for 5 minutes. Add 2 drops Bf (b), stir well, spread out the drop and leave until the iodine colour has disappeared. Add 6 drops of (c) , stir thoroughly, then remove about half the volume of the liquid, by means of a capillary tube, and drop on the centre of a 12.5-cm. filter-paper. When the liquid has finished spreading, add 4 drops of (d) to the centre of the cobalticyanide precipitate.In presence of tin, a yellowish band moves outwards until spreading ceases, then transformation occurs and the yellow ring turns red from the outer edge; for tin contents above 1 per cent., the whole of the area bounded by the ring also appears red. Notes on Method-The transferred precipitate should be light buff or greenish-blue in colour. The transformation, or development time, varies somewhat for different percentages of tin, e.g., more than 0.3 per cent. of tin gives a colour almost immediately, 0.3 to 0.1 per cent. takes about 1 minute to give a colour and less than 0.1 per cent. may take 3 or 4 minutes; full development of the colour takes place within 5 minutes of addition of the “dithiol’ ’ reagent.Tried on: Samples Nos. 44, 22, 21, 46, 47, 48, 49, 50, 51, 52,” 53,* 1*-Tin present; Nos. 6, 40, 19, 4, 37, 16, 15, 54, 55, 14, 13, 56, 11, 42, 36, 34, 35, In absence of tin the paper remains white. all results positive. 57-Tin less than 0.06 per cent. and all results negative. * First discovered by spot-tests and subsequently confirmed by chemical analysis.[Vol. 75 194 EVANS AND HIGGS: SPOT-TESTS FOR THE IDESTIFICATIOS OF (IV) IRON Reagents-(a) Diluted nitric acid (spgr. 1.20). (b) Potassium cyanide solution (20 per cent.), 2 vols.; sodium hydroxide solution (20 per cent.), 1 vol. (c) Ammonium nitrate solution (5 per cent.). (d) Ammonium thiocyanate solution (10 per cent .) , 2 vols ; hydrochloric acid (sp.gr. 1-16), 1 vol. Method-Add 2 drops of (a) to the cleaned surface and allow to react for 3 or 4 minutes. Transfer the drops of acid t o the well of a glazed p(orce1ain spot-plate, add 6 drops of mixture ( b ) , stir well until all the blue copper hydroxide has been converted to double cyanide, and add more reagent ( b ) if necessary to complete the solution of hydroxide.Specimens con- taining neither iron nor manganese give a water-white solution, nickel in Large amounts imparts a yellow colour, and high tin contents result in formation of a white precipitate. Iron gives a brown precipitate of ferric hydroxide, often no more than a brown coloration for contents below about 0.1 per cent.; however, coagulation occurs on standing, and a slight precipitate may be seen. Manganese, when present, gives a dark brownish-black precipitate, completely masking any iron that may be present; hence further treatment is necessary to distinguish the iron.Transfer the dark brownish manganese precipitate to the centre of a No. 541 filter-paper (or any filter-paper that does not give an iron reaction with thiocyanate), and wash 3 or 4 times with 1-drop washings of (c). To the washed precipitate add 2 drops of ( d ) ; a red coloration develops in presence of iron, but if manganese alone is present, it merely dissolves in the acid leaving the paper white. Tried on: Samples Nos. 15, 11, 1, 6, 58, 59, 49, 21, 32, 51, 50, 48, lo,* 35,* 5,* 27," Nos. 40,25,28,37,22,42,45,44-1ron absent and all results negative. Reagents-(a) Concentrated nitric acid (sp.gr. 1.42), 1 vol.; tartaric acid solution (50 per cent.), 1 vol. ( b ) Distilled water. (c) Sodium chromate solution (5 per cent. in water). 4*-1ron present ; all results positive. (V) LEAD Method-To the surface of the cleaned specimen add 2 drops of (a), leave until the reaction appears to be completed, then add 3 drops of (b) followed by 2 drops of (c), stir well and leave for a few seconds. Transfer the drop and precipitate, if any, by means of a capillary tube, to the centre of a close-grained filter-paper in such a manner that each drop is allowed to spread completely before the next drop is added; finally, wash tvyice with 3 drops of ( b ) . In presence of lead, a yellow patch is visible at the centre of the paper; when wet, the paper usually has an outer yellow band of excess reagent, but this is completely reduced to tervalent chromium during the drying process.In absence of lead, or for lead contents below about 0.15 per cent., the paper is exactly as described above but without a central yellow patch. Tried on: Samples Nos. 21, 48, 51, 49-Lead present ; all results positive. NOS. 50, 22, 11, 17, 20, 1!3, 15, 6, 45, 44, 14, 13, 16, 1, 52, 42, 40- Lead less than 0.16 per cent. and all results negative. Reagewds-(a) Concentrated nitric acid (sp.gr. 1.42), 1 vol. ; syrupy phosphoric acid (sp.gr. 1-75), 1 vol. (VI) SILICON ( b ) Distilled water. (c) Ammonium chloride solution (saturated). (d) Rhodamine B solution7 (0.05 per cent. in water). (e) Ammonium chloride solution (5 per cent.), 1 vol.; hydrochloric acid solution (5 per cent.), 1 vol.Method-Add 2 drops of (a) to the cleaned surface and leave to react for at least 5 minutes, add 3 drops of ( b ) , stir, then tilt the specimen and allow the drops to fall on to a clean watch- glass, scraping the surface of the specimen to remove any adhering particles. Add 4 drops of (c), stir, and follow with 4 drops of (d), stir again thoroughly and leave for 5 minutes for * Iron first found by spot-tests and subsequently confirmed by chemical analysis.April, 1950' ALLOYING ELEMENTS I N COPPER-BASE ALLOYS 195 precipitation and absorption to be completed. Transfer the reaction solution, by means of a capillary tube, dropwise on to the centre of a filter-paper, supported on the open mouth of a beaker. Wash by dropping 2 drops of (c) on to the centre from near the surface of the paper; repeat twice with 2-drop washings and finally with 3 or 4 1-drop washings of ( e ) ; the last washing treatment clears out any precipitated reagent leaving the centre quite clear in the absence of silicon.The presence of silicon is indicated by the formation of a deep magenta- coloured absorption precipitate, which dries to a light magenta spot against a pale pink back- ground, I t has been found that when cobalt is present, as well as silicon, there is a tendency towards formation of a black matrix, which is quite insoluble in all acid mixtures except those containing hydrofluoric acid. Our reluctance to employ such a dangerous acid compels us, for once, to accept a test which is not quite specific, but which has never been known to fail in absence of cobalt.In presence of cobalt, a black precipitate without other indications of silicon would suggest that silicon may be a constituent of the alloy. Tried on: Samples Nos. 60, 35, 61, 62, 63, 64, 65, 66,* 67,* 75,* 76,* 77," 78, 79- Nos. 40, 49, 6, 19, 51, 11, 22, 50, 68-Silicon less than 0.1 per cent. The papers when dried can be kept indefinitely. Silicon present ; all results positive. and all results negative. (VII) NICKEL Reqents--(a) Brominated hydrochloric acid (sp.gr. 1-20). (b) Diluted ammonia solution (1 + I ) , 3 vols.; ammonium phosphate solution (10 per cent.), 1 vol. (c) Alcoholic dimethylglyoxime solution (saturated). (d) Diluted ammonia solution (1 + 9). Method-Attack the cleaned surface with 1 drop of ( a ) and leave until the bromine colour has been dispelled. Add 2 drops of ( b ) , or sufficient to make the drop alkaline (test with a fragment of litmus paper), stir, then follow with 4 or 5 drops of (c) and stir again.The nickel glyoxime precipitate can be plainly seen from as little as 0.5 per cent. of nickel; however, it is better, as a matter of routine, to transfer the drops to the centre of a filter-disc and to wash three or four times with (d); by this procedure a slight dirty pink precipitate can be obtained from nickel contents down to 0.08 per cent, The background colour of the paper is a light greenish-yellow with an outer emerald-green edge. In absence of nickel, the centre of the paper is free from coloured precipitate. Tried on: Samples Nos. 56, 42, 43, 69, 70, 71, 59, 11, 54, 72, 57, 58, 74, 19, 73, 39, 34, Kos. 33, 15, 16, 1, 36, 22, 13, 14, 51, 52-Nickel absent and all 21, 48-Nickel present ; all results positive.results negative. (VIII) L4LUMINIUM AND BERYLLIUM Keageitts-(a) Brominated hydrochloric acid (sp.gr. 1-16>. (b) Sodium hydroxide solution (20 per cent.), 1 vol.; potassium cyanide solution (10 per cent .), 2 vols. (c) Sodium hydroxide solution (5 per cent.). (d) Ammonium chloride solution (20 per cent.). (e) Ammonium chloride solution (20 per cent.), 1 vol.; ammonium citrate solution (50 per cent.), 1 vol. (f) Ammonium aurine tricarboxylate solution (0.1 per cent. in alcohol). (g) Ammonium citrate solution (50 per cent.). PyeParalioth of veagent paper-Pipette 1 ml. of reagent (f) on to a 12.5-cm.filter-paper (preferably No. 541), causing the liquid to spread as evenly as possible whilst attempting to concentrate the reagent into a wet patch approximately 8 to 9 cm. in diameter; dry over a source of hot air. Method-Place 1 drop of (a) on the cleaned surface and leave to react for 5 minutes. Add 4 to 5 drops of (b), stir well until the original white precipitate has dissolved; the solution should now be alkaline and quite clear, except in presence of iron when a brownish-black * Only black cobalt-silicide ( ?) was visible.196 precipitate will be observed. prepared reagent paper supported on the open mouth of a beaker. ALUMINIUM- Transfer the filter-paper to a white glazed tile, moisten a 9-cm. filter-disc with reagent (d), place flat on the wet patch of the reagent paper and ensure thorough contact by rolling a glass rod over the papers.Remove the upper ammonium chloride paper, discard, replace the reagent paper on its beaker and leave for 1 minute. In absence of both aluminium and beryllium the paper becomes perfectly white. Aluminium is indicated by a broad band of scarlet, approximately 1-5 to 2-6 inches in diameter, the inner edge being slightly irregular and slightly paler in colour. Beryllium, when present with aluminium, is indicated by a narrow irregular ring, always just inside the inner edge of the aluminium band and of a more intense scarlet colour; the remainder of the paper is white. BERYLLIUM- To confirm the presence of beryllium, repeat the test but, after the transferred liquid has finished spreading, treat with 2 drops of (c), which causes the beryllium ring to become twisted into a scalloped pattern.Transfer to a glazed tile, soak a 9-cm. filter-disc with mixture (e), place over the reagent paper and ensure thorough contact at all points by rolling with a glass rod; leave for 1 minute, remove the chloride - citrate paper and discard. Place the reagent paper on its beaker and wash once with (g) by allowing the liquid to flow readily from a capillary tube whilst describing a circle, just inside the coloured area. The broad band due to aluminium is completely bleached by this treatment and, after about 5 minutes, the paper is completely white in absence of beryllium. Beryllium is indicated by a narrow irregular reddish-scarlet ring, the colour of which seems to be enhanced by the ammonium citrate treatment; the aluminium colour remains bleached even when the paper is dry.Tried on: Samples Nos. 11, 36, 34, 6, 54, 80, 81, 73, 59, 68, 82, 83, &Q, 56-Aluminium Nos. 1, 19, 45, 16, 17, 22, 15, 12, 14, 13, 10-Aluminium absent Nos. 38,55, 66,68, 85, 86, 87,88, 89,90,91,92,93,94,95-Beryllium Nos. 11, 36, 34, 6, 54, 80, 81, 73, 59, 58, 82, 83, 84, 56-Beryllium Note-In all instances of aluminium and beryllium being present together, both reactions EVANS AND HIGGS: SPOT-TESTS FOR THE IDENTIFICATION OF [Vol. 75 Transfer the alkaline solution dropwise to the centre of a present ; all results positive. and all results negative. present ; all results positive. absent and all results negative. were clearly visible. (IX) ARSEKIC Reagents-(a) Diluted nitric acid (sp.gr.1.20), 1 vol. ; potassium ferricyanide solution (10 per cent.), 1 vol. ( b ) Diluted sulphuric acid (1 + 3). (c) Mercuric chloride solution (saturated). (d) Zinc metal (arsenic-free and previously treated as detailed below). (i) Preparation of reagent pa$er-Soak a filter-paper in reagent ( c ) , hang up to drain off excess of the reagent, and allow to dry; brush off loose crystals of mercuric chloride and cut the paper into small strips of approximateky 1.5 x 0.25 inches. (ii) Preparation of metallic zinc-Boil small lumps of granulated zinc in a 1 per cent. solution of cadmium sulphate for a few minutes, remove and wash the zinc, and store under distilled water until required for the test. Method-Place 4 drops of (a) on the cleaned surface, the liquid being spread out immediateZy, as far as possible, with a pointed glass rod.Leave to react for a few seconds until it turns semi-solid, and then immediately scrape off on to a watch-glass, rinsing the specimen with a few drops of distilled water, which is rubbed vigorously on the surface to remove as much as possible of any film there may be. In absence of arsenic, etc., the mass detaches easily, leaving the copper clean; but if a.rsenic is present, it deposits rapidly on the metal and is then extremely difficult to remove; this in itself is a very good preliminary test for arsenic. Stir the liquid in the watch-glass and transfer, by means of a capillary tube, to a wide test tube, rinse in with a little water followed by an amount of (b) equal in volume to the aqueous solution already present.Close the mouth of the test tube with a rubberApril, 19501 ALLOYING ELEMENTS IN COPPER-BASE ALLOYS 197 stopper carrying a short length (about 2.5 inches) of glass tubing, closed at both ends by cotton-wool plugs, and holding between the plugs a strip of reagent paper. Insert a few small lumps of prepared reagent (d) into the test tube, replace the rubber stopper and leave for half an hour; if required, add more solid zinc, but without removing the stopper for longer than necessary. The presence of arsenic is indicated by an orange stain at the bottom end of the strip, tailing off into yellow. In absence of arsenic the paper remains white. Tried on: Samples Nos. 14, 96, 97, 98, 99-Arsenic present ; all results positive.Nos. 1, 35, 13, 33, 19, 90, 69, 22, 82-Arsenic absent and all results negative. (X) CADMIUM Reagents-(a) Diluted nitric acid (sp.gr. 1-20), (b) Sodium hydroxide solution (20 per cent.). (c) Potassium cyanide solution (20 per cent.). ( d ) Dinitrodiphenylcarbazide8 solution (saturated alcoholic solution). (e) Formalin solution (37 to 41 per cent.). Meth,od-Place 2 drops of (a) on the cleaned surface of the specimen and leave to react for 3 minutes. Shake the drop into the well of a white glazed spot-plate, add 2 drops of ( b ) , which should render the drops alkaline to litmus, follow with 5 or 6 drops of (c), or sufficient only to dissolve the blue cupric hydroxide completely; the majority of any iron or manganese present will remain as light brown and dark brown precipitates respectively.Add 1 drop of (d) followed by 4 or 5 drops of (e) and stir well until the reddish-brown colour has been dispelled. Cadmium gives a deep green or greenish-blue coloration, developing quickly into a greenish-yellow solution and a blue precipitate. In absence of cadmium, the liquid assumes a greyish-brown colour, slowly developing into a light dirty-brown precipitate and a greyish- brown solution. Tried on: Samples Nos. 41, 13, 7, 100, 101-Cadmium present; all results positive. Nos. 40, 35, 54, 21, 22, 11, 1, 43, 37, 16, 19, 15, 45, 38, 60-Cadmium absent and all results negative. (XI) COBALT lieagenfs-(a) Broniinated hydrochloric acid (sp.g. 1 *IS). (b) Sodium hypophosphite (solid). (c) Ammonium thiocyanate (solid).(a) Ethyl alcohol. (e) isoPropy1 alcohol. Method-Place 1 drop of (a) on the cleaned surface of the specimen, stirring continuously with a pointed glass rod until the drop has become practically white (or fawn). Transfer the drop to a watch-glass, rinse in with 3 or 4 drops of distilled water and add a further drop or two of (a) until the liquid is clear. Add approximately 0.1 g. of (b), and stir until dissolved, follow with about the same quantity of (c) and again stir well. Drop the mixture on to the centre of a filter-disc, supported on the open mouth of a beaker, keeping the solid confined as closely as possible to the centre of the wet patch. Wash four times with 2 or 3-drop quantities of (d). Any notable amount of cobalt, q., about 2 per cent., is manifested at this stage by the formation of light blue rings passing outwards from the centre; the fourth wash concentrates the cobalt as a band close to the outer edge of the wetted patch.No indication is obtained at this stage from 0.2 per cent. of cobalt. The colour with ethyl alcohol is transient and rapidly disappears. When dry, treat the edge of the paper with a few drops of (e), then tilt the paper so as to let the liquid run towards the centre of the paper; where the isopropyl alcohol cuts the cobalt ring the blue colour is at once reformed. This colour, though transient, is somewhat more permanent than that with ethyl alcohol; it is most vivid as the alcohol dries. The lower limit of 0-2 per cent. is revealed, by careful examination, as a faint blue ring on the outside edge of the paper.In absence of cobalt, or when cobalt is present in quantities less than that stated above, no blue colour is at any stage produced. Tried on : Samples Nos. 66, 67, 68, 75, 76, 77, 78, 79-Cobalt present ; all results positive. Nos. 1, 17, 22, 15, 48, 52, 54, 42, 55, 14, 13, 16-Cobalt absent and Hang up the paper to dry. all results negative.198 EVANS AND HIGGS: SPOT-TESTS FOR THE IDENTIFICATION OF (XII) CHROMIUM [Vol. 76 Reagents-(a) Diluted nitric acid (sp.gr. 1.20). (b) Diluted sulphuric acid (1 + ,3). (c) Bromine water. (a) Sodium hydroxide solution (20 per cent.). (e) Diphenylcarbazide solution (1 per cent. in glycerol), 1 vol.; diluted sulphuric acid (1 + 3), 1 vol. Method-Attack the cleaned sample with 2 drops of (a) and leave until the attack is complete.Gently remove the liquid by means of capillary tube and add 2 drops of (b) to the deposit on the copper surface; after about 1 to 2 minutes, crystals of copper sulphate separate out of solution. Stir the liquid to detach the crystals, etc., and transfer to a clean watch- glass. Add 2 or 3 drops of (c), or until present in excess, then follow with 3 or 4 drops of (d), which should make the mixture alkaline; if not, more alkali is added until a blue reaction is obtained with litmus paper. Place a 126-cin. filter-disc, previously soaked in bromine water and dried, on the open mouth of a beaker and treat the centre with 3 drops of ( e ) . Prepare a filter-tube, consisting of a short length of glass tubing, approximately 0.75 x O-Sinch, into the end of which is pressed some filter-paper pulp; place this tube over the wet reagent patch and filter through it the alkaline liquid obtained above, wash once with 3 drops of water, remove the tube and discard it. Add 6 to 8 drops of (e) equidistant from the centre of the wet patch and just inside the wet area.Chromium is indicated by an immediate formation of purple crescents at the interface between the alkali chromate and the acid diphenyl- carbazide. The coloured pattern of the paper takes the following design: at the centre of the paper is a small colourless area surrounded by a light pinkish band (probably the alkaline reagent colour), which is more pronounced in a.bsence of chromium. Immediately outside the pink band appears the purple colour of chromium, if present; and further out still is the yellow glycerol - reagent colour.The alkaline solution does not spread out uniformly, but tends to break through the periphery at certain points to form a series of inlets, All papers tend to develop a purplish colour after standing for some time, but as little as 0.2 per cent. of chromium should show clearly by the time filtration has ceased. In absence of chromium, the paper appears as described above but without the purple bands just outside the alkaline pink area. Tried on: Samples Nos. 16, 37, 102, 103, 104, 105-Chromium present; all results Nos. 43, 41, 4, 14, 11, 25, 45, 19, 49, 6, 21, 60, 22, 40-Chromium positive. absent and all resuits negative. (XIII) PHOSPHORUS Reagents-(a) Ammonium persulphate (solid). (b) Diluted ammonia (1 + 3).(c) Potassium cyanide solution (10 per cent.). ( d ) Diluted nitric acid (sp.gr. 1.:20). ( e ) Ammonium molybdate solution (10 per cent.). (f) Diluted, boiled out, nitric acid solution (5 per cent.). (g) Stannous chloride solution (5 per cent. in 10 per cent. hydrochloric acid). Method-Place a little of the solid (a) on the surface of the cleaned specimen and dissolve in 2 drops of (b), stir, and leave to stand for 3 to 5 minutes. Add 4 or 5 single drops of (c), stir well after each addition; if any blue or green precipitate remains unattacked, a further addition of cyanide should be made; leave for 5 minutes with occasional stirring. Transfer the liquid to a watch-glass, acidify with 2 drops of (d), stir, then follow with a small quantity of (a), stir again, and leave for a few minutes.As a rule this results in a clear solution, but if there is a precipitate still unattacked, add a little more persulphate and a third drop of (d). Regardless of whether there is still any precipitate, the process is proceeded with. One drop of (e) is added and thoroughly stirred, and allowed to stand with occasional stirring for a t least 10 minutes. Transfer the liquid, slowly in a dropwise manner, to the centre of a filter-paper, to localise the precipitate to a small. spot, wash with four 1 or 2-drop ,quantities of (f). When the spreading of the wash-liquor has ceased, add 2 or 3 drops of (g) , whereupon phosphorus is indicated by a blue spot approximately 1 inch in diameter. High siliconApril, 19501 ALLOYING ELEMENTS IN COPPER-BASE ALLOYS 199 contents may also result in the formation of zi blue spot, but this spot is washed out into a large, faintly blue area by continued treatment with (g).Arsenic, if not completely removed by re-deposition on the sample, shows up as a blue ring at the outer edge of the paper upon drying. In absence of phosphorus there is no blue spot at the centr'e of the paper. The presence of iron, manganese or nickel may result in a brown spot at the centre of the paper, but this should not obscure any reaction due to phosphorus. Tried on: Samples Nos. 20, 22-Phosphorus present ; both results positive. or less than 0.05 per cent. and all results negative. Nos. 21, 14, 11, 43, 1, 82, 63, 13, 15, 40, 45, 9-Phosphorus absent SUMMARY Tests have been described for the alloying elements in copper-base alloys.The elements so detected are manganese, zinc, tin, iron, lead, silicon , nickel, aluminium, beryllium, arsenic, cadmium, cobalt , chromium and phosphorus. With the alloys at our disposal all the tests have proved specific and unambiguous, with the exception of silicon which cannot be detected directly in presence of large amounts of cobalt, but the presence of a black insoluble precipitate, when cobalt is known to be present, would indicate silicon. A new separation of aluminium and beryllium has been described which may provide a useful analytical procedure for the estimation of beryllium in presence of aluminium. Thanks are due to the Chief Scientist, Ministry of Supply, for permission to publish this paper, and also to Johnson Matthey & Co., Ltd., for the supply of Mallory alloys, 73,84 and 100.APPENDIX SPECIMENS OF ALLOYS USED IN THE TESTS No. Sample 1 Mn4 2 M n 3 3 Mn2 4 RLN 5 RLQ 6 TAHU 7 880 8 h h 5 9 MNP 10 "7" 11 TAHG 12 Cu/Ni 13 RLP 14 RLO 16 SFP 16 SDQ 17 RLH 18 RBP 19 CuSb 20 P 6 21 D F L l 22 DRF 23 SEC 24 RLK 25 SEB 26 SEA 27 SDT 28 SDZ 29 S 898 30 S897 31 S896 32 L11 33 IC 34 RBS 35 RBT 36 RBP Mn Zn Sn 28.8 15 6 4.75 2-3 2-17 1 1.0 0.4 0.10 0.15 - 1-72 0.08 ? ? ? ? - - - - 31.3 0.06 0.03 - ? ? ? ? 40 - - - - - 4.7 - 30.7 - - - - - - - 5-10 5.65 - 2-08 9-71 - 14-6 2.1 17.9 - - 12.5 - 8-81 - 2.26 5.12 - 4.82 - 0.59 - - 0.62 - 0.19 - 0.04 0.30 - 0.01 0.26 - - (0.10 - 1.15 <0*10 - - - - - - Constituents, per cent.No. Sample 37 SDP 38 S876 39 RBR 40 Copper 41 S 883 42 GM 43 RRG 44 Speculum 45 CuSn 46 RLR 47 RLK 48 RYB 49 CMC 50 TNR 51 COB 62 S 2 3 53 OZN 54 SDU 55 Cu/Be 66 DDU 57 SDW 58 SDX 59 SDY 60 SDK 61 RLM 62 S 15 63 S 12 64 RLL 65 S 11 66 MA 100 67 MA 84 68 MA73 69 RRJ 70 RRH 51 SDM 72 SDO 73 RBQ 74 SDN 75 922 76 923 77 924 78 925 79 926 80 5 81 4 82 3 83 2 84 1 85 865 86 866 87 867 88 868 89 869 90 870 91 871 92 872 93 873 95 875 96 884 97 885 98 886 99 887 100 881 101 882 102 RLD 103 RLE 104 RLF 105 RLG 94 a74 EVANS AND HIGGS: SPOT-TESTS FOR THE IDENTIFICATION OF APPENDIx--continued Mn Zn Sn Fe Pb - - - - I - - - - - - I _ _ - - - - 50.0 - - - 15.0 - - - 5.2 - - 2-10 - ' - 0.50 >0*10 2.05 0.22 1.50 0.06 0.16 0.12 1.84 0.73 - 0.04 - - - - - - - _ . - 0.45 - 0.21 - - I - - ? - ? - ? - - - - - - - - - - -- - - - - - - - - - - - - - - - - I - - - - - - - - - - - - - 1.66 - 4.13 - 2.48 - 1.17 - 1.68 - 1.16 - 1-10 - 0.70 - 0.31 - 1.44 -- 2.43 - 0.38 - 0.22 - 0.19 - 0.49 - ? - ? - - - - - - - - - I-Vol. 75 0.22 -April, 19501 ALLO\-ING ELEMENTS I N COPPER-BASE ALLOYS 201 1. 2. 3. 4. 5 . 6. 7. 8. REFERENCES Evans, B. S., and Higgs, I). G., Analyst, 1945, 70, 75-82. , , Ibid., 1946, 71, 464-474. , Ibid., 1947, 72, 101-105. , Ibid., 1947, 72, 105-109. Ibid., 1947, 72, 439-443. -- I I -- -- -- , Clark, R. E. D., Ibid., 1936, 61, 242. Eegriwe, E.. 2. anal. Chenz., 1927, 70, 400. Feigl, F., “Qualitative Analysis by Spot Tests,” 2nd English Edition, Nordniarin Publishing Co., Febvzrary, 1950 Inc., New York, 1939, p. 49.