Crucibles treatment

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. 

It is usually preferable to oxidise the compound directly as follows. Intimately mix 0 02-0 05 g. of the eompound with 3 g. of sodium peroxide and 2 g. of anhydrous sodium carbonate in a niekel erucible. Heat the crueible and its eontents with a small flame, gently at first, afterwards more strongly until the eontents are fused, and eontinue heating for a further 10 minutes. Allow to stand, extract the contents of the crucible with water, and filter. Add exeess of eoneentrated nitrie acid to the filtrate and test with ammonium molybdate reagent as above. A yellow preeipitate indicates the presenee of phosphorus. It must be borne in mind that the above treatment 1 eonvert any arsenie present into arsenate. 

The residue consists of the impurities, and the loss in weight of the crucible gives the amount of pure silica present, provided that the contaminants are in the same form before and after the hydrofluoric acid treatment and are not volatilised in the operation. Although silicon is not the only element that forms a volatile fluoride, it is by far the most abundant and most often encountered element consequently the volatilisation method of separation is generally satisfactory. 

The precipitate, collected in a sintered-glass (porosity No. 4) or porcelain filtering crucible, may be weighed more rapidly as follows. Wash the copper(I) thiocyanate five or six times with ethanol, followed by a similar treatment with small volumes of anhydrous diethyl ether, then suck the precipitate dry at the pump for 10 minutes, wipe the outside of the crucible with a clean linen cloth and leave it in a vacuum desiccator for 10 minutes. Weigh as CuSCN. 

The reduction is avoided by first charring the paper without inflaming, and then burning off the carbon slowly at a low temperature with free access of air. If a reduced precipitate is obtained, it may be re-oxidised by treatment with sulphuric acid, followed by volatilisation of the acid and re-heating. The final ignition of the barium sulphate need not be made at a higher temperature than 600 800 °C (dull red heat). A Vitreosil or porcelain filtering crucible may be used, and the difficulty of reduction by carbon is entirely avoided. 

Double-cell system, in soil and ground water treatment, 25 835 Double crucible technique, 11 135-136 Double-deck kiln, 15 530 Double-drum dryers, 9 134 Double-drum separator, 15 446 Double-effect distillation, 10 153 Double end point titration method,... 

In this method lg dried soil in a silica crucible is mixed with 5ml 0.2N sodium hydroxide and 10ml absolute ethanol and left to evaporate on a hot plate for 12h. The residue is digested with 0.6N sulphuric acid. After treatment with ethylene oxide and acetonitrile the acetonitrile layer is recovered. 

Cory Neth, an analyst for the City of Lincoln, Nebraska, Wastewater Treatment Plant Laboratory, removes a tray of crucibles from a muffle furnace. The crucibles are filtering crucibles used in the determination of suspended solids. The muffle furnace is used in the total suspended volatile solid test. 

The Fig. 8 a shows tools for reshaping crucibles after use. During physical and chemical treatment crucibles are often deformed, especially noble metal. This results in a loss of good heat transfer to the thermocouple which records the temperature during experiments. Plastic tools are available for reshaping crucibles. 

Synthesis of sulfo-selenide Chevrel phases Phases ofM Mo x xSex composition (M = Cr, Mn) were prepared by the reaction of stoichiometric mixtures of MoS2 and MoSe2 binary powders with Mo and Cr, or Mn, metallic powders (Mantjour-Billah and Chevrel 2004). The mixtures were pressed into pellets and then (inside an alumina crucible) sealed in evacuated silica tubes. After heating to 800°C and then to 1000°C for 24 hours, two further grinding and annealing (at 1000°C) treatments were performed. Powder X-ray diffraction methods were used to study the solid solutions, the trend of the lattice parameters, etc. 

Peligot then heated the anhydrous chloride with potassium in a closed platinum crucible. This was heroic treatment for the platinum, to be sure, for the reaction was violent enough to make crucible and contents white-hot. However, since he took care to place the small... 

The synthesis of the n=2 phase is similar to that described above for the n=l system. In general, stoichiometric portions of oxides and carbonates (or nitrates) are ground and reacted in a high density alumina crucible at temperatures between 800 and 820°C. The product is crushed and pressed into a pellet for further heat treatments at 840-870°C. The firing temperature must be raised incrementally to prevent melting of the sample. 

The transportable vitrification system (TVS), operated in the USA, uses a Joule-heated ceramic melter (Whitehouse et al. 1995), which has been proposed for installation in other countries as well. However, a cold-crucible melter has also been considered for waste treatment in the USA, Italy, and Korea (Jouan et al. 1998). 

Moisten the residue with ca 10 ml of acetone, slant the dish at ca 45° angle and ignite. Remove the gas burner, cool the dish, and repeat the above treatment. Heat the crucible on a gas burner or in a muffle furnace until the disappearance of carbonaceous matter, cool in a desiccator and weigh (Ref 1)... 

This treatment removes the tecracene. Dry the crucible the residue in an oven at 60 5° for 30 mins, cool in a desiccator and weigh(D). Calc % Tetracene on a moisture-free basis... 

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