Chloroplatinate , ammonium

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. 

Method 1. From ammonium chloroplatinate. Place 3 0 g. of ammonium chloroplatinate and 30 g. of A.R. sodium nitrate (1) in Pyrex beaker or porcelain casserole and heat gently at first until the rapid evolution of gas slackens, and then more strongly until a temperature of about 300° is reached. This operation occupies about 15 minutes, and there is no spattering. Maintain the fluid mass at 500-530° for 30 minutes, and allow the mixture to cool. Treat the sohd mass with 50 ml. of water. The brown precipitate of platinum oxide (PtOj.HjO) settles to the bottom. Wash it once or twice by decantation, filter througha hardened filter paper on a Gooch crucible, and wash on the filter until practically free from nitrates. Stop the washing process immediately the precipitate tends to become colloidal (2) traces of sodium nitrate do not affect the efficiency of the catalyst. Dry the oxide in a desiccator, and weigh out portions of the dried material as required. 

Ammonium chloroplatinate often can be used to advantage in place of chloroplatim c acid in the preparation of Adams catalyst. A mixture of 3 g. of ammonium chloroplatinate and 30 g. of sodium nitrate in a casserole or Pyrex beaker is heated gently at first until the rapid evolution of gas slackens and then more strongly until a temperature of 500° is reached. This operation requires about fifteen minutes and there is no spattering. The temperature is held at 500-520° for one-half hour and the mixture is then allowed to cool. The platinum oxide catalyst, collected in the usual way by extracting the soluble salts with water, weighs 1.5 g. and it is comparable in appearance and in activity to the material prepared from chloroplatinic acid. 

This procedure is particularly time-saving when scrap platinum or spent catalyst is used for the preparation of platinum oxide, for after conversion to chloroplatinic acid a purification is conveniently effected by precipitating the ammonium salt, and the direct fusion of this with sodium nitrate eliminates the tedious process of reconversion to chloroplatinic acid. Furthermore ammonium chloroplatinate is not hygroscopic and can he accurately weighed. The amount of catalyst obtained is almost exactly half the weight of the ammonium salt employed. 

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. 

When NH4C1 is added to a solution of platinum tetrachloride, sparingly soluble ammonium chloroplatinate is obtained, which on ignition gives spongy platinum. 

Compounds Ammonium chloroplatinate sodium chloroplatinate platinic chloride platinum chloride sodium tetrachloroplatinate potassium tetrachloroplatinate ammonium tetrachloroplatinate sodium hexachloroplati-nate potassium hexachloroplatinate ammonium hexachloroplatinate... 

Palladium was discovered in 1803 by W.H. Wollaston during refining and purification oP platinum metal. This new metal was found in the aqua regia extract of native platinum and was detected in solution after platinum was precipitated. It was removed as ammonium chloroplatinate. Treating this solution with mercurous cyanide precipitated a yellow palladium complex salt. The precipitate was washed and ignited to form palladium metal. Wollaston named the element palladium after the newly discovered asteroid Pallas. 

Dr. Wollaston dissolved a portion of crude platinum in aqua regia, and neutralized the excess acid with caustic soda. He then added sal ammoniac to precipitate the platinum as ammonium chloroplatinate, and mercuric cyanide to precipitate the palladium as palladious cyanide. After filtering the precipitate, he decomposed the excess mercuric cyanide in the filtrate by adding hydrochloric acid and evaporating to dryness. When he washed the residue with alcohol, everything dissolved except a beautiful dark red powder, which proved to be a double chloride of sodium and a new metal (3), which, because of the rose color of its salts, Dr. Wollaston named rhodium (9). He found that the sodium rhodium chloride could be easily reduced by heating it in a current of hydrogen, and that after the sodium chloride had been washed out, the rhodium remained as a metallic powder. He also obtained a rhodium button. 

Chloro - pentammino - platinic Chloride, [Pt(NH3)8CI]Cl3, is produced along with hexammino-platinic chloride by the action of liquid ammonia on ammonium chloroplatinate in a closed tube, keeping the materials dry. The mixture of the two platinic derivatives is separated by crystallisation, as the chloro-pentammino-derivative is more soluble in water than the hexammino-derivative. 

Adams platinum oxide catalyst is readily prepared from chloroplatinio acid or from ammonium chloroplatinate, and is employed for catalytio hydrogenation at pressures of one atmosphere to several atmospheres and from room temperature to about 90°. Reduction is usually carried out with rectified spirit or absolute alcohol as solvents. In some cases (e.g., the reduction of benzene, toluene, xylene, mesitylene, cymene and diphenyl ), the addition to the absolute alcohol solution of 2-5 per cent, of the volume of rectified spirit which has been saturated with hydrogen chloride increases the effectiveness of the catalyst under these conditions chlorobenzene, bromobenzene, o-, m- and p-bromotoluenes, p-dichloro- and p-dibromo-benzene are reduced completely but the halogens are simultaneously eliminated. Other solvents which are occasionally employed include glacial acetic acid, ethyl acetate, ethyl acetate with 17 per cent, acetic acid or 8 per cent, of alcohol. In the actual hydrogenation the platinum oxide Pt02,H20 is first reduced to an active form of finely-divided platinum, which is the real catalyst allowance must be made for the consumption of hydrogen in the process. 

Platinum residues from hydrogenation reactions should be carefully preserved and subsequently recovered by conversion into ammonium chloro-platinate by the following method. Dissolve the platinum or platinum residues in aqua regia, evaporate just to dryness several times with concentrated hydrochloric acid, dissolve the final residue in a little water and filter. Precipitate ammonium chloroplatinate from the filtrate by addition of excess of a saturated solution of ammonium chloride. Filter and dry the precipitate at 100°C. 

In the belief that the action of the enzyme might be modified by the presence of some of the more prevalent metals in trace amounts, the effects of cations on mammalian /3-glucuronidase were re-investigated186 195 of a large number studied, only Cu , Ag , and Hg were pronounced in their effects. (Inhibition was also seen with uranium acetate, ammonium chloroplatinate, osmium tetroxide, and sodium tungstate.83) Marked inhibition was seen with 2.5 X 10-6 M of Ag and 1.5 X 10 6 M of Hg00, and inhibition by these two ions was reversed by tissue constituents. 

We now brought our chemist, T. Krigas, in to isolate and identify these products. He clearly identified it as a platinum-containing compound, probably ammonium chloroplatinate [NH4]2[PtCl6]. We were somewhat nonplussed, however, when addition of this compound at the detected concentration to bacterial cells in test-tube cultures led, not to filamentation, but to bacteriocidal activity. Many experiments later we found that a solution of this compound, after standing on our laboratory shelf for a few weeks, was able to produce a small amount of short filaments. 

When potassium nitrate and potassium chloroplatinate were used in the fusion, no bronze was formed.The only species detected by X-ray diffraction were platinum metal and a Pt02. A report that the use of ammonium chloroplatinate in the fusion gave a better catalyst than when chloroplatininic acid was used might also have been the result of an inhibition of bronze formation by the ammonium salt. ... 

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