Graphite dishes

Strontium metal is not found in its elemental state in nature. Its salts and oxide compounds constitute only 0.025% of the Earths crust. Strontium is found in Mexico and Spain in the mineral ores of strontianite (SrCO ) and celestite (SrSO ). As these ores are treated with hydrochloric acid (HCl), they produce strontium chloride (SrCy that is then used, along with potassium chloride (KCl), to form a eutectic mixture to reduce the melting point of the SrCl, as a molten electrolyte in a graphite dish-shaped electrolysis apparatus. This process produces Sr cations collected at the cathode, where they acquire electrons to form strontium metal. At the same time, Cl anions give up electrons at the anode and are released as chlorine gas Cl T. 

Figure 7.5. Graphite dish used to grow crystals in the belt furnace.

Three approaches were made to identify systems capable of containing phosphate melts. [Ca(P03)2]n melts were contained in ceramic vessels. This was successful for melts of 100 lb or less, but could not be used for production quantities. Graphite dishes and a hearth furnace were satisfactory for both [Ca(P03)2]/i and [NaCa(P03)3] melts, but there are reasons to believe that maintenance may have become expensive. 

The best indirect, but seldom used, method is to determine the total moisture separately in a Penfteld tube, determine the loss on ignition in air at 825—875°C, and report graphitic carbon as percent loss on ignition (100 — %moisture — %ash). It is desirable to use a platinum dish for ignition loss and it... 

Amongst other devices used to produce the required atoms in the vapour state are the Delves cup which enables the determination of lead in blood samples the sample is placed in a small nickel cup which is inserted directly into an acetylene-air flame. The tantalum boat is a similar device to the Delves cup in this case the sample is placed into a small tantalum dish which is then inserted into an acetylene-air flame. The use of these devices, especially for small sample volumes, has now been largely superseded by the graphite furnace. 

Lead Determine as directed for Method II in the Atomic Absorption Spectrophotometric Graphite Furnace Method under Lead Limit Test, Appendix IIIB, using a 10-g sample. Nonvolatile Residue Evaporate 80 mL (about 100 g) of sample to dryness in a tared dish on a steam bath, dry the residue at 105° for 30 min, cool, and weigh. 

Glassy carbon Graphite <500 Glassy carbon is used in the form of crucibles and dishes for alkaline melts and as receptacles for wet decomposition procedures... 

Products and Uses A heavy metal used in paint pigment, solder, pool cue chalk, crayons from China, glazes on ceramic dishes and bowls, among other products. Prohibited from interstate commerce since the middle 1970s. It is still manufactured and used locally. Lead has been found in wines, possibly from the foil used on bottles. (Pencil "lead" is not lead at all rather it is a mixture of graphite and clay.) Prevents bottom growth on boat hulls and rust development on metal. Used as a filler and for radiation protection. 

In an attempt to determine how the actual number of resonance neutrons inside the furnace relative to those outside varied with temperature, caused by the different temperature-dependence of absorption by the carbon and other materials, two types of check experiments were made. At each temperature several bombardments were made of the cyclotron monitor, the 10-cm monitor, and the hot-dish monitor, but with no uranium present, leaving a hole in the graphite where its uranium oxide sphere was otherwise placed. These experiments were not very accurate, but they show that for a given bombardment of the furnace the number of neutrons absorbed by a hot iodine or Ga sample inside the hot furnace is the same within 8 percent as when the furnace is cold. 

One of the reactors uses the dished electrode membrane concept (section 2.7.3) (Fig. 7.26). It employs thirty-four cathodes, each 1 m in area and fabricated from Hastelloy C276 the plate anodes are DSA (Ru02/Ti02)-coated titanium. The other reactor is a Deutsche Carbone cell, which utilizes graphite anodes and cathodes. 

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