Platinizing solution

Thin-layer Chromatography. System TA—Rf 53 system TB—Rf 08 system TC—Rf 59 system TD—Rf 51 system TE—Rf 63 system TF—Rf 47. Dragendorff spray, positive acidified iodo-platinate solution, positive acidified potassium permanganate solution, positive.)... 

Prcxiuced as a dark-brown precipitate by passing HgS through a hot solution of HgPtCla in hydrochloric acid. The precipitation can be greatly accelerated and made almost quantitative if the weakly acidic platinate solution is mixed with a 5% solution of MgClg and then saturated with HgS gas. After the excess HgS is driven off by boiling, the PtSg is filtered off and carefully dried. 

Preparation of the electrode surfaces is very important. The electrodes should be cleaned in an acid cleaning solution, rinsed thoroughly with distilled water, and immersed in a platinizing solution. DC voltage is adjusted to give a moderate evolution of gas for about 20 seconds, after which the polarity is reversed. The reversal process is repeated until a gray (not black) deposit of platinum has formed on the surface. Too heavy a deposit should be avoided because spongy platinum will absorb unwanted chemical species. 

For a platinized Pt-based Clark-type NO microsensor (13), the surface of a bare Pt disk electrode is electrochemically platinized by cyclic voltammetry in a platinizing solution (3% chloroplatinic acid in water). As the potential is scanned (from -t-0.6 to -0.35 V vs. Ag/AgCl) using cycUc voltammetry (see Chapter 11), Pt(TV) ions are electroplated on the bare Pt disk electrode to create a porous and roughened electrode surface. The platinized Pt electrode has a larger active surface area as demonstrated by the larger recorded currents and lower detection limits for NO measurements compared with bare Pt electrodes as shown in Figme 6.3.10.1. 

The preparation of platinized electrodes consists of depositing colloidal platinum (platinum black) upon the working surfaces. This is accomplished by the use of conventional electroplating techniques. The electrode to be platinized is connected as the cathode, and a piece of pure platinum sheet forms the anode of an electrolytic cell. Kohlrausch and Holborn formula platinizing solution is employed as the electrolyte. Its chemical composition is platinum chloride (H2PtCl2) 3 % dissolved in 0.025 % lead acetate solution. This platinizing solution may be obtained in 2-oz bottles from the Hartman-Leddon Co. in Philadelphia or from the Arthur H. Thomas Co., also of Philadelphia. 

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. 

Nicotine may be detected by the colourless, crystalline mercurichloride obtained when an aqueous solution is added to a solution of mercuric chloride, by the black precipitate formed under similar conditions with potassium platinic iodide and the characteristic crystalline periodide, BI2. HI, m.p. 123°, produced on admixture, under specified conditions, 2 of ethereal solutions of nicotine and iodine (cf Anabasine, p. 43). A polarographic study of nicotine has been made by Kirkpatrick. ... 

The (ZZ-ephedrine was resolved into its components by the use of d-and Z-mandelic acids. In 1921 Neuberg and Hirsch showed that benz-aldehyde was reduced by yeast, fermenting in suerose or glueose solution to benzyl aleohol and a phenylpropanolone, which proved to be Z-Ph. CHOH. CO. CH3. This ean be simultaneously, or consecutively, eondensed with methylamine and then eonverted to Z-ephedrine by reduction, e.g., with aluminium amalgam in moist ether, or by hydrogen in presenee of platinic oxide as catalyst (Knoll, Hildebrant and Klavehn ). 

Dissolve about i gram of an organic base (brucine, strychnine, quinine, c.) in 10 c.c. of a mixture of equal volumes of concentrated hydrochloric acid and water. To the clear hot solution add excess of platinic chloride and let it cool. Yellow microscopic crystals of the chloroplatinate of the base separate. (If the chloroplatinate of the base is very soluble in water, such as aniline, it must be washed with strong hydrochloiic acid, pressed on a porous plate and dried in a vacuum-desiccator over solid caustic potash.)... 

Cyan-kalium, n. potassium cyanide, -kalium-losung, /. potassium cyanide solution, -ko-balt, m. cobalt cyanide, -kohlensaure, / cyanocarbonic acid. -kupfer, n. copper cyanide, -laugerei, -laugung, /. cyaniding. cyanidation. -losung, / cyanide solution, -metall, n. metallic methyl cyanide, -natrium, n. sodium cyanide. -platin, n. platinum cyanide. 

Catalytic hydrogenation. Aqueous solution of FMN (50 pM) containing a small amount of platinized asbestos is babbled with hydrogen gas for 10-20 minutes, until the yellow color and green fluorescence of FMN completely disappear. A suitable setup for this purpose can easily be constructed using a small flask, a rubber septum and two syringe needles (used as the inlet and outlet of H2 gas). 

Sometimes the term normal hydrogen electrode (and respectively normal potential instead of standard potential) has been used referring to a hydrogen electrode with a platinized platinum electrode immersed in 1 M sulfuric acid irrespectively of the actual proton activity in this solution. With the latter electrode poorly defined diffusion (liquid junction) potentials will be caused, thus data obtained with this electrode are not included. The term normal hydrogen electrode should not be used either, because it implies a reference to the concentration unit normal which is not to be used anymore, see also below. 

Modified hotocatal3 sts were prepared using commercial P25 and synthesized Ti02. The modification was carried out in two different methods, i.e. platinization with H2PtCl6 solution and metallization with leached solution from wasted catalytic converter. 

The photocatalytic reactivity for TCE decomposition was increased by platinization and the photocatalytic activity of the catalysts prepared with leached solution fi-om wasted automobile catalyst was similar to that of the catalysts modified with H2PtCl6. 

Suspensions of semiconductors with heterojunctions formed by CdS or solid solution ZnyCdi-yS and Cu , S have been prepared and tested as photocatalysts for photochemical hydrogen production [278]. With platinized powders of Zno.nCdo.ssS/CujS in solution containing both S and SOj ions, hydrogen was generated concomitantly with thiosulfate ions with quantum yield of about 0.5. 

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