Magnesium fusion

The determination of carbon and arsenic in organic compounds using magnesium fusion and the elemental analysis of organoarsines and organobromoarsines have been... 

Magnesium Fusion. Arrange a hard-glass tube as in Figure 37. The delivery tube reaches just above the water, which is acidified with 5 drops of dilute hydrochloric acid. Mix 0.1 g of the sample to be tested with 0.2 g of a mixture of equal parts of mag-... 

The chromates of the alkali metals and of magnesium and calcium are soluble in water the other chromates are insoluble. The chromate ion is yellow, but some insoluble chromates are red (for example silver chromate, Ag2Cr04). Chromates are often isomorph-ous with sulphates, which suggests that the chromate ion, CrO has a tetrahedral structure similar to that of the sulphate ion, SO4 Chromates may be prepared by oxidising chromium(III) salts the oxidation can be carried out by fusion with sodium peroxide, or by adding sodium peroxide to a solution of the chromium(IIl) salt. The use of sodium peroxide ensures an alkaline solution otherwise, under acid conditions, the chromate ion is converted into the orange-coloured dichromate ion ... 

Thermal Properties. Because all limestone is converted to an oxide before fusion or melting occurs, the only melting point appHcable is that of quicklime. These values are 2570°C for CaO and 2800°C for MgO. Boiling point values for CaO are 2850°C and for MgO 3600°C. The mean specific heats for limestones and limes gradually ascend as temperatures increase from 0 to 1000°C. The ranges are as follows high calcium limestone, 0.19—0.26 dolomitic quicklime, 0.19—0.294 dolomitic limestone, 0.206—0.264 magnesium oxide, 0.199—0.303 and calcium oxide, 0.175—0.286. 

Wood ash generally contains calcium, potassium, phosphoms, magnesium, and siUca. Ashes recovered from burned wood are - 25% water soluble and the extract is strongly alkaline. The ash fusion temperature is in the range of 1300 to 1500°C. 

Ash fusion characteristics are important in ash deposition in boilers. Ash deposition occurring on the furnace walls is termed slagging, whereas accumulation on the superheater and other tubes is termed fouling. A variety of empirical indexes have been developed (60,61) to relate fouling and slagging to the ash chemical composition through parameters such as acidic and basic oxides content, sodium, calcium and magnesium, and sulfur. 

Salt formation. The resin acids have a low acid strength. The pa s (ionization constants) values of resin acids are difficult to obtain, and values of 6.4 and 5.7 have been reported [23] for abietic and dehydroabietic acids, respectively. Resin acids form salts with sodium and aluminium. These salts can be used in detergents because of micelle formation at low concentrations. Other metal salts (resinates) of magnesium, barium, calcium, lead, zinc and cobalt are used in inks and adhesive formulations. These resinates are prepared by precipitation (addition of the heavy metal salt to a solution of sodium resinate) or fusion (rosin is fused with the heavy metal compound). 

Many solid substances (camphor, iodine, naphthalene, etc.), are known which are appreciably volatile at ordinary temperatures. Others, such as the metals, are apparently quite fixed, but they probably possess a definite, although very small vapour-pressure, even at ordinary temperatures. Thus, if magnesium is heated to 550° for a few hours in a magnesia boat enclosed in a vacuous tube it sublimes in beautiful crystals on the cool part of the tube. The vaporisation of a solid without previous fusion is called sublimation the vapour-pressure (like the vapour-pressure of a liquid), is definite for each temperature, is independent of i the volume of the vapour space, and increases with rise of temperature. 

Slag modifiers raise the fusion point or sintering temperature of the ash and directly neutralize any S03 formed. They are based on alkaline-earth metals such as magnesium, calcium, and strontium, or rare-earth metals such as cerium they are available as oxides, salts, or soaps. 

Carbon fusion produces neon, sodium and magnesium via reactions of the following type ... 

Once the helium has been used up, the same process is repeated. The star cools, the core collapses further and heats up, and new fusion processes are ignited carbon and oxygen are fused to make sodium, magnesium, silicon, and sulphur. Gradually, the Periodic Table emerges in this juddering, unstable furnace. 

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