Platinum 58 Residue

Method- 3. From platinum metal or platinum residues. Dissolve the platinum metal or platinum residues in aqua regia, evaporate just to dryness several times with concentrated hydrochloric acid, dissolve the final residue in a httle water and precipitate as ammonium chloro-platinate with excess of saturated ammonium chloride solution. Filter and dry the precipitate at 100°. Then proceed according to Method 1. 

It is advisable to test a small portion of the filtrate for platinum by acidifying with hydrochloric acid and adding a few drops of stannous chloride solution a yellow or brown colour develops according to the quantity of platinum pVesent. The yellow colour is soluble in ether, thus rendering the t t more sensitive. If platinum is found, treat the filtrate with excess of formaldehyde and sodium iQrdroxide solution and heat,- platinum black septarates on standing and may be filtered and worked up with other platinum residues (see Method 3). 

Platin-plattierung,/. platinum plating, -reihe, /. platinum series, -rhodium, n. platinum-rh ium. -rohr, n.,-rohre,/. platinum tube, -rtickstand, m. platinum residue, -salmiak, m. ammonium chloroplatinate, -salz, n. platinum salt, -sand, m. sand for cleaning platinum, -saure, /. platinic acid, -schale. 

Ruthenium was recognized as a new element hy G.W. Osann in 1828. He found it in insoluhle residues from aqua regia extract of native platinum from alluvial deposits in the Ural mountains of Russia. He named it Ruthen after the Latin name Ruthenia for Russia. The discovery of this element, however, is credited to Klaus who in 1844 found that Osann s ruthenium oxide was very impure and isolated pure Ru metal from crude platinum residues insoluhle in aqua regia. 

In 1840 Klaus became interested in platinum residues. The reader will recall that in 1828 Professor G. W. Osann of Dorpat University had announced the presence in these residues of three new metals, the... 

The reagent is prepared by dissolving 2 6 g hydrated chloroplatinic acid H2[PtCl6]. 6H20 in 10 ml water. Owing to its expensive character, only small quantities should be employed and all precipitates placed in the platinum residues bottle. 

For the determination of platinum, the condenser was replaced by a 1 cm. silica tube which tapered to 5 mm. The apparatus was flushed with nitrogen then hydrogen was passed through it, the emergent gas being burnt. The platinum residue was heated to constant weight (Found F, 32-4 Pt, 57-5. PtOjF, requires F, 33-4 Pt, 57-2%). 

In order to reclaim platinum residues from the laboratory (e.g., platinum absorbed on filter papers, scraps, filter ash, etc.), these are well ignited and then sieved through a fine screen, separating the residues into fine and coarse fractions. 

Wohler obtained phosphorus by strongly heating a mixture of sand and bone-black (calcium phosphate and carbon) — the modern process, now carried out in the electric furnace. He prepared artificial nickel arsenide and worked on the separation of iridium and osmium in a pound of platinum residues given him by Dumas on a visit to Paris in 1833. A supposed silver suboxide, Ag40, prepared by Wohler by the action of caustic potash solution on a supposed subcitrate made by heating silver citrate in hydrogen at 100°, was not analysed and was probably a mixture of silver and silver oxide AggO the red colour of the solution of the subcitrate was probably due to colloidal silver. ... 

Osann investigated the part of Russian native platinum insoluble in aqua regia, and in 1827 claimed to have discovered three new metals ruthenium, polinium, and pluranium. He sent a specimen to Berzelius (with whom he had worked), but since Berzelius found nothing new in it, Osann withdrew his claim in 1829. "The platinum residues were re-investigated by Claus, who by working up 15 lb. in a research begun in 1840, discovered in them in 1844 new metal for which he retained Osann s name ruthenium. ... 

In 1828 G. V. Ozann, Professor of the Tartu University, studied the residue obtained after the dissolution of crude Uralian platinum in aqua regia and found that it contained three new elements pluranium, polinium, and ruthenium. But Berzelius, to whom Ozann had sent a letter about his findings, did not support the discovery. Because of this significant fact the study of this platinum residue was not renewed until 1841. Berzelius s prestige was so high that no chemist in the world would argue with him. 

K. Klaus began his research in 1840. The then Minister of Finance of Russia E.F. Kankrin, a competent and energetic person, rendered him great assistance Klaus obtained 2 pounds of crude platinum residue and extracted a considerable amount of iridium, rhodium, osmium, and palladium from it, apart from 10% platinum. In addition, Klaus separated a mixture of metals which, in his opinion, had to contain a new substance. 

Alternatively, the bulk of the platinum in the aqueous residues can be precipitated by ammonium chloride as ammonium chloroplatinate, the latter filtered off, and the filtrate evaporated to dryness. The chloroplatinate and the residue from the evaporation are then ignited. 

Place a solution of 10 -4 g. of benzalacetophenone, m.p. 57° (Section IV,130) in 75 ml. of pure ethyl acetate (Section 11,47,15) in the reaction bottle of the catalytic hydrogenation apparatus and add 0 2 g. of Adams platinum oxide catalyst (for full experimental details, see Section 111,150). Displace the air with hydrogen, and shake the mixture with hydrogen until 0 05 mol is absorbed (10-25 minutes). Filter oflF the platinum, and remove the ethyl acetate by distillation. RecrystaUise the residual benzylacetophenone from about 12 ml. of alcohol. The yield of pure product, m.p. 73°, is 9 g. 

If an appreciable amount of residue remains, note its colour. Add a few drops of water and test the solution (or suspension) with htmus or with Universal indicator paper. Then add a httle dilute hydrochloric acid and observe whether efiervesceiice occurs and the residue dissolves. Apply a flame test with a platinum wire on the hydrochloric acid solution to determine the metal present. (In rare cases, it may be necessary to subject a solution of the residue to the methods of qualitative inorganic analysis to identify the metal or metals present.) If the flame test indicates sodium, repeat the ignition of the substance on platinum foil. 

Evidence of the organic nature of the substance may, be provided by the behaviour of the compound when heated on porcelain or platinum or other comparatively inert metal (e.g., nickel) the substance is inflammable, burns with a more or less smoky flame, chars and leaves a black residue consisting largely of carbon (compare Ignition Test above). 

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