Platinum wire

Each newly cleaved mica surface is very clean. Flowever, it is known that mica has a strong tendency to spontaneously adsorb particles [45] or organic contaminants [46], which may affect subsequent measurements. The mica sheets are cut into 10 nun x 10 nun sized samples using a hot platinum wire, then laid down onto a thick and clean 100 nun x 100 nun mica backing sheet for protection. On the backing sheet, the mica samples can be transferred into a vacuum chamber for themial evaporation of typically 50-55 mn thick silver mirrors. 

Hydrazine is prepared, anhydrous and in good yield, by glow discharge electrolysis of liquid ammonia a platinum cathode is immersed in liquid and a platinum wire anode is mounted just... 

The apparatus (Fig. 82), which is constructed throughout of glass, consists of a pear-shaped bulb A (of about 5 ml. capacity) in which the solution is boiled, and which has a short length of platinum wire fused through its lowest point to assist steady boiling. The bulb A is connected near its base by a curved narrow tube B to a vertical condenser C, and from its apex by a similar tube D, undulating as shown, to the cup E. A larger outer cup F is fused to the lower neck of E as shown. 

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. 

The noble metal thermocouples, Types B, R, and S, are all platinum or platinum-rhodium thermocouples and hence share many of the same characteristics. Metallic vapor diffusion at high temperatures can readily change the platinum wire calibration, hence platinum wires should only be used inside a nonmetallic sheath such as high-purity alumina. 

Since detailed chemical structure information is not usually required from isotope ratio measurements, it is possible to vaporize samples by simply pyrolyzing them. For this purpose, the sample can be placed on a tungsten, rhenium, or platinum wire and heated strongly in vacuum by passing an electric current through the wire. This is thermal or surface ionization (TI). Alternatively, a small electric furnace can be used when removal of solvent from a dilute solution is desirable before vaporization of residual solute. Again, a wide variety of mass analyzers can be used to measure m/z values of atomic ions and their relative abundances. 

Some of the characteristics of the SPRT, as an iaterpolation device for the ITS-90, have been discussed. In order to meet these requirements, the thermometer must be made from almost ideally pure platinum wire mounted ia a physical coastmctioa which will keep it ia a straia-free coaditioa. The coaveatioaal resistance 25.5 Q or some convenient submultiple is historical over limited ranges it permitted a rough but quick estimate of temperature, because a 1-K change is nearly equivalent to a 0.1-Q change. 

Platinum has many uses in dentistry. Pure platinum foil serves as the matrix in the constmction of fused-porcelain restorations. Platinum foil may be laminated with gold foil for cold-welded foil restorations. Platinum wire has found use as retention posts and pins in crown and bridge restorations. Heating elements and thermocouples in high-fusing porcelain furnaces are usually made of platinum or its alloys (see Platinum-GROUP metals). 

Electrolysis Reactions. The electrodes in electrophoresis equipment are typically constmcted from platinum wire, and sodium chloride generally carries the bulk of the current in any electrophoretic medium. This results in the reactions... 

Hexafluoroetbane [76-16-4] M 138.0, b -79°. Purified for pyrolysis studies by passage through a copper vessel containing C0F3 at ca 270°, and held for 3h in a bottle with a heated (1300°) platinum wire. It was then fractionally distd. [Steunenberg and Cady J Am Chem Soc 74 4165 1962.]... 

A device based on flame ionization measures the total concentration of hydrocarbons. By using a catalyst, such as a heated platinum wire, hydrocarbons other than methane can be removed from the sample gas. With a platinum catalyst, these hydrocarbons are oxidized at a lower temperature than methane. Hence, the total concentration of hydrocarbons, methane, and hydrocarbons other than methane can be determined. 

It consists of a boiling-tube, thiough the bottoni-stout platinum wire is sealed, which is intenclcd... 

This apparatus can only be used with sodium light, as for quantitative results light of definite refrangibility must be used. A Bunsen lamp of convenient construction, into the flame of which a little common salt can be introduced on a platinum wire, is placed about 4 or 5 inches from the... 

According to U.S. Patent 2,966,493, the 2,3-bis-(3-pyridyl)-2,3-butanedlol used as the starting material may be prepared as follows. A solution of 1,430 g of 3-acetyl-pyridine in 7,042 ml of a 1 N aqueous solution of potassium hydroxide is placed into a cathode chamber containing a mercury cathode with a surface of 353 cm and is separated from an anode chamber by an Alundum membrane. As anode a platinum wire is used and the anolyte consists of a 1 N solution of aqueous potassium hydroxide which Is replenished from time to time. 

Platinum coatings may also be thermally sprayed or sputtered onto the titanium, to provide uniform well-bonded coatings. Titanium rod may also be spiral wound with platinum wire. However, the use of these techniques is limited. 

The hydrogen electrode consists of an electrode of platinum foil (approximately 1 X 1 X 0-002 cm) welded to a platinum wire which is fused into a glass tube. In order to increase its catalytic activity it is platinised by making it cathodic in a solution of chloroplatinic acid (2% chloroplatinic acid in 2 N HCl) frequently lead acetate is added to the solution (0-02%) and this appears to facilitate the deposition of an even and very finely divided layer... 

One form of calomel electrode is shown in Fig. 15.1(a). It consists of a stoppered glass vessel provided with a bent side tube fitted with a three-way tap which carries a short upper and a long lower tube the latter is drawn out to a constriction at the bottom end. A short platinum wire is fused into the bottom of the vessel so that it protrudes into the interior, and a narrow glass tube sealed to the bottom of the vessel is bent round parallel to the vessel. A little mercury placed in the bottom of this tube provides electrical connection with the interior of the vessel through the sealed-in platinum wire. Mercury and mercury compounds must be handled with care (see Section 16.8). 

---