Crucible, crucibles

Untersetzscherbe, /. plate or saucer set under something, (for crucibles) crucible stand. Unterspannung, /. (Elec.) undervoltage, low tension. 

Materials ring stand, ring, clay triangle, crucible, crucible tongs, Bunsen burner, balance, 3.0 g baking soda (NaHC03)... 

Figure 28-9 Automated apparatus that fuses three samples at once over propane burners. It also provides mechanical agitation of the Pt/Au crucibles. Crucibles are shown in the tipped position used to pour contents out after fusion is complete. [Courtesy Spex Industries. Edison, NJJ...

Both types of differential scanning calorimeters make use of a crucible to contain the sample. The reference is either an inert material in a crucible of the same type as that used for the sample or simply the empty crucible. Crucibles commonly measure 5-6 mm in diameter, which gives some idea of the overall dimensions of the DSC cell. 

If the minimum pressure attained by the vacuum pump is 10 atm (lo.l N/m ), which of the crucible/crucibles can be used to obtain aluminium-free steel ... 

Alundum is used for highly refractory bricks (m.p. 2000-2100 C), crucibles, ref ractory cement and muffles also for small laboratory apparatus used at high temperatures (combustion tubes, pyrometer tubes, etc.). 

Noack volatility (lubricants) T 60-161 Weight of a crucible before and after evaporation... 

When silica is fused,. silica glass is formed. This has advantages over ordinary glass in that it is much less easily fused (it softens at about 1800 K). and has a very low coefficient of expansion. It is. therefore, used for crucibles and other articles required to be infusible... 

The extraction of titanium is still relatively costly first the dioxide Ti02 is converted to the tetrachloride TiCl4 by heating with carbon in a stream of chlorine the tetrachloride is a volatile liquid which can be rendered pure by fractional distillation. The next stage is costly the reduction of the tetrachloride to the metal, with magnesium. must be carried out in a molybdenum-coated iron crucible in an atmospheric of argon at about 1100 K ... 

Picric acid is used on a large scale as a high explosive, but for this purpose requires a detonator. If a few small crystals of the pure acid are heated on a crucible lid, they first melt, and ultimately burn harmlessly with a smoky flame. Metallic salts of picric acid are much less stable than the free acid,... 

Heat a small portion of the following substances on an inverted porcelain or stainless steel crucible lid. At first, heat one side of the lid gently so that the heat travels along the lid to the organic substance later heat the lid more strongly. Note carefully in particular [a) the change in appearance, (b) whether readily inflammable, (r) any odour produced, (d) wliether a non-volatile residue is left. 

Aqueous solutions do not usually ignite even though the solute is highly inflammable, e.g., an aqueous solution of ethanol containing less than 50% of the latter. When aqueous solutions of solid substances are heated on a crucible lid, they usually "spit" vigorously immediately before solidification. 

A mist of condensed water on the upper portion of the tube A indicates the presence of hydrogen. To detect the presence of hydrogen in this way, however, the copper oxide must first be strongly heated in a crucible and then allowed to cool in a good desiccator otherwise the water normally absorbed by the very hygroscopic copper oxide will always give a mist on the tube A. 

Sodium Fusion on Semi mlcro Scale. The Lassaigne test can be readily carried out with as little as 0 01 g. of material, using sodium pellets about 2 mm. in diameter in a tube about 3 x. After fusion, the red-hot tube is plunged into distilled water in a small porcelain crucible or in a boiling tube. The mixture is then heated, filtered and tested as already described. 

The silver salts of most carboxylic acids are only sparingly soluble in cold water, and hence are readily prepared. Moreover they very rarely contain water of crystallisation, and therefore when dried can be analysed without further treatment. The analysis itself is simple, rapid and accurate, because gentle ignition of a weighed quantity of the silver salt in a crucible drives off the organic matter, leaving a residue of pure metallic silver. 

A simple apparatus for sublimation in a stream of air or of inert gas is shown in Fig. II, 45, 3.. d is a two-necked flask equipped with a narrow inlet tube B with stopcock and a wide tube C 12-15 inm. in diameter. The latter is fitted to a sintered glass crucible and the usual adapter and suction flask E. A well-fitting filter paper is placed on the sintered glass filter plate to collect any sublimate carried by the gas stream. 

The apparatus consists essentially of a cast iron crucible and cover or fusion pot in which is placed a nickel crucible or dish. The complete apparatus is illustrated in Fig.//, 1. The fusion pot A carries a... 

A suitable cast iron crucible and cover, 1 quart capacity, is supplied by the Denver Fire Clay Compsiny, Denver, U.S.A. It can also be made from sheet iron. 

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. 

The impurity is potassium chloride. The approximate acid content is determined by heating a weighed sample of the acid in a crucible gently at first and finally at a red heat until no trace of black residue remains, and weighing the white residual potassium chloride. 

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