Platinum oxide, brown

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. 

A solution containing 26.3 mg of vitamin 6,2 in 15 ml of water was shaken with 78 mg of platinum oxide catalyst and hydrogen gas under substantially atmospheric pressure at 25 C for 20 hours. Hydrogen was absorbed. During the absorption of hydrogen the color of the solution changed from red to brown. The solution was separated from the catalyst and evaporated to dryness in vacuo. The residue was then dissolved in 1 ml of water and then diluted with about 6 ml of acetone. 

Platinum oxide (2) was reduced as required. Four batches were used, with colors ranging from yellow-brown to almost black. 

Adams Platinum Oxide (by Adams et a/.).148 In a porcelain casserole is prepared a solution of 3.5 g of chloroplatinic acid in 10 ml of water, and to this is added 35 g of sodium nitrate.The mixture is evaporated to dryness while stirring with a glass rod. The temperature is then raised to 350-370°C within 10 min. Fusion takes place, brown oxides of nitrogen are evolved, and a precipitate of brown platinum oxide gradually separates. After 15 min, when the temperature has reached about 400°C, the evolution of gas has gently decreased. After 20 min the temperature should be 500-550°C. The temperature is held until about 30 min have elapsed, when the fusion should be complete. The mass is allowed to cool and is then treated with 50 ml of water.The brown precipitate settles to the bottom and can be washed by decantation once or twice, then filtered, and washed until practically free from nitrates. If the precipitate becomes colloidal, it is better to stop washing immediately at that stage. The oxide is either used directly or dried in a desiccator. The yield is 1.57-1.65 g (95-100% of the theoretical amount). 

The brown platinum oxide Pt02-H20, the Adams catalyst, when treated with H2 gives a very finely divided black suspension of metal. The reagent is used in acetic acid or ethanol for the hydrogenation of alkenes. 

The black solid was always accompanied by a pale brown sohd. This was obtained in much greater purity by fluorinating platinum dioxide and analysis indicated that it was platinum oxide trifluoride. 

The Fluorination of Platinum in the Presence of Powdered Glass.—Fluorine, diluted with nitrogen, was passed in a slow stream over a heated mixture of powdered glass and platinum at 400° and a mixture of pale brown and black particles was left. J -Ray powder photographs showed these particles were two phases. A simple pattern, characteristic of the black material, was indexed on the basis of a rhombohedral unit-cell, a = 5-39 i 0 02 A, a = 54-7 i 0-2°, / = 97 A. Observed and calculated Ijd" values are in Table 3. The complex pattern of the light brown phase was identical with that of platinum oxide trifluoride. 

Am. Chem. Soc. 73, 5913 (J95l) by catalytic hydrogenation of pure cyclopentanone with copper chromite at 150 and 150 atm Kogl, Ultee, Rcc. Trav. Chim. 69, 1576 (1950) by catalytic hydrogenation of cyclopentanone with platinum oxide and platinum black at 2-3 atm Noller, Adams, J. Am. Chem. Soc. 48, 1084 (1926) by hydration of cyclopen-tene in aq H2S04 Hepp. US. pat. 2,414,646 (1947 to Phillips Petr.) by reduction of cyclopentanone with LiAlH4 in ether at room temp NyStrom, Brown, J. Am. Chem. Soc. 69, 1197 (1947). 

A 10% solution of HsPtCla (10 ml.) is added to 9 g. of NaNOa in a 50-ml. beaker. The solution is evaporated to dryness over a flame (covered with asbestos-wire gauze) while continuously stirring with a glass rod. Local melting of the mixture must be carefully avoided. Then 100 g. of NaNOa is heated to 520°C in a 400-ml. beaker (controlling the temperature with a thermocouple), and the dry, fine powder residue from the evaporation is added at once. The flame is then removed. The olive-brown platinum oxide is... 

Fuse chloroplatinic acid with sodium nitrate to form brown platinum oxide. 

The brown oxide is a heavy granular powder which settles to the bottom of the solution in the bottle in which the reduction is carried out (p. 10). It must be reduced to platinum black before it becomes a catalyst for the reduction. When the hydrogen is admitted and the bottle shaken the brown oxide becomes black and whips up into a fine suspension. The time necessary for the change of the oxide to platinum black is called the lag. The time of lag varies usually from several seconds to two or three minutes, depending upon the conditions under which... 

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