Crucibles preparation

In any case, the sample is usually contained in a crucible (prepared in advance by ignition without a sample) and placed in the oven or over the Meker burner for a specified period of time or to a constant weight, as in the loss on drying. The calculation is also similar to loss on drying, and the weight of the crucible will need to be subtracted if the tare feature of a balance is not used. 

Neutralize 100 cc. of the wine with N NaOH soln., calculating from the acidity, 44, the number of cc. of N alkali necessary for the neutralization. If the volume of the soln. is increased more than 10% by the addition of the alkali, evaporate to approximately 100 cc. Add to the neutralized soln. 0.075 S tartaric acid for each cc. of N alkali added and after the tartaric acid has dissolved add 2 cc. of glacial acetic acid and 15 g. of KC1. After the KC1 has dissolved, add 15 cc. of 95% alcohol stir vigorously until the K-bitartrate begins to precipitate and let stand in an ice-box at 15-18° for at least 15 hours. Decant the liquid from the separated K-bitartrate on a Gooch crucible prepared with a very thin film of asbestos, or on filter paper in a... 

Preparation of the crucible Preparation of the stove Ingredients and closing of the crucible Heating and ingestion of the elixir Other uses of the elixir... 

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. 

Europium is now prepared by mixing EU2O3 with a 10%-excess of lanthanum metal and heating the mixture in a tantalum crucible under high vacuum. The element is collected as a silvery-white metallic deposit on the walls of the crucible. 

Charcoal is generally satisfactorily activated by heating gently to red heat in a crucible or quartz beaker in a muffle furnace, finally allowing to cool under an inert atmosphere in a desiccator. Good commercial activated charcoal is made from wood, e.g. Norit (from Birch wood), Darco and Nuchar. If the cost is important then the cheaper animal charcoal (bone charcoal) can be used. However, this charcoal contains calcium phosphate and other calcium salts and cannot be used with acidic materials. In this case the charcoal is boiled with dilute hydrochloric acid (1 1 by volume) for 2-3h, diluted with distilled water and filtered through a fine grade paper on a Buchner flask, washed with distilled water until the filtrate is almost neutral, and dried first in air then in a vacuum, and activated as above. To improve the porosity, charcoal columns are usually prepared in admixture with diatomaceous earth. 

CNTs have been prepared recently by electrolysis and by electron irradiation of tube precursors. For example. Hsu e/ al. [30,31] have described the condensed-phase preparation of MWCNTs by an electrolytic method using a graphite rod (cathode) and carbon crucible (anode) (Fig. 6) in conjunction with molten LiCl as the electrolyte, maintained at 600°C under an Ar atmosphere. Application of a dc current (3-20 A, <20 V) for 2 min yielded MWCNTs (2-10 nm in diameter, >0.5 pm in length) consisting of 5-20 concentric layers with an interlayer... 

For the preparation of samples for X-ray fluorescence spectroscopy, lithium metaborate is the preferred flux because lithium does not give rise to interfering X-ray emissions. The fusion may be carried out in platinum crucibles or in crucibles made from specially prepared graphite these graphite crucibles can also be used for the vacuum fusion of metal samples for the analysis of occluded gases. 

Pipette 25.0 mL of the bromide ion solution (0.01-0.02M) into a 400 mL beaker, add excess of dilute silver nitrate solution, filter off the precipitated silver bromide on a sintered glass filtering crucible, and wash it with cold water. Dissolve the precipitate in a warm solution prepared from 15 mL of concentrated ammonia solution, 15 mL of 1M ammonium chloride, and 0.3 g of potassium tetracyanonickelate. Dilute to 100-200 mL, add three drops of murexide indicator, and titrate with standard EDTA (0.01 M) (slowly near the end point) until the colour changes from yellow to violet. 

B. Determination of tellurium Procedure. The solution should contain not more than 0.2 g tellurium in 50 mL of 3M hydrochloric acid (ca 25 per cent by volume of hydrochloric acid). Heat to boiling, add 15 mL of a freshly prepared, saturated solution of sulphur dioxide, then 10 mL of a 15 per cent aqueous solution of hydrazinium chloride, and finally 25 mL more of the saturated solution of sulphur dioxide. Boil until the precipitate settles in an easily filterable form this should require not more than 5 minutes. Allow to settle, filter through a weighed filtering crucible (sintered-glass, or porcelain), and immediately wash with hot water until free from chloride. Finally wash with ethanol (to remove all water and prevent oxidation), and dry to constant weight at 105 °C. Weigh as Te. 

Zirconium ( > 100 mg in ca /. M sulphuric acid solution). Add freshly prepared 10 per cent aqueous diammonium hydrogenphosphate solution in 50-100-fold excess. Dilute to 300 mL, boil for a few minutes, allow to digest on a water bath for 15-30 minutes and cool to about 60 °C. Filter through a quantitative filter paper, wash first with 150 mL of 1M sulphuric acid containing 2.5 g diammonium hydrogenphosphate and then with cold 5 per cent ammonium nitrate solution until the filtrate is sulphate-free. Dry the filter paper and precipitate at 110°C, place in a platinum crucible and carefully burn off the filter paper. Finally heat at 1000 °C for 1-3 hours and weigh as ZrP207 (Section 11.51). 

Elements dissolved in boron influence its crystal structure. Dissolved impurities also influenee the physical and chemical properties of boron, especially the electrical properties, because boron is a semiconductor. Preparation of solid solutions in jS-rh boron requires a careful choice of crucible material. To avoid contamination, boron nitride or a cold, coinage-metal crucible should be used or the levitation or floating-zone melting techniques applied. 

The synthetic method used in preparing a particular boride phase depends primarily on its intended use. Whereas for basic research borides of high purity are desirable, for industrial applications, e.g., in coatings, tools and crucibles, as a refining agent in metallurgy or in control rods in nuclear energy plants, pure borides are unnecessary. 

---