Fire Clay Crucibles

Mix 100 g. of granulated aluminum with 90 g. of clean line sand and 90 g. of sulfur. Place the mixture in a fire-clay crucible embedded in sand in a safe place and ignite with fuse powder and a magnesium ribbon, as described in Exercise 85. After the reaction is completed, allow the crucible to cool. Break the crucible, put the contents in an evaporating dish, and treat with water to decompose the aluminum sulfide. This should be done under the hood so that the copious fumes of poisonous H2S will be carried off. Wash away the slimy lumps of melted aluminum from such foreign matter as pieces of crucible. Place these pieces of metal in a beaker, gradually treat with commercial hydrochloric acid until the action has quieted down, then cover with the acid and let stand on the hot plate for several days,... 

Method of Obtaining Heat—Bottles—A Chemical Balance—Test Tube Racks—A Ring Stand—A Hydrogen Sulphide Generator — Necessary Apparatus — Test Tubes — Evaporating Dishes—Fire Clay Crucibles—Filter Paper—Graduated Cylinder—Chemical Thermometers—Pipette—Red and Blue Litmus Paper—Beakers—Pinch Cocks—Thistle Tubes—Flasks— Clamps—Chemicals for the Laboratory. Pages 40-62... 

A small fire clay crucible of about 25 c.c. capacity is a useful little article to have about the laboratory and it is capable of standing much higher temperatures than ordinary glassware, and for this reason it can be used where ordinary chemical glassware would be unsuitable. 

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. 

The fusion pot is obtainable on the market from the Denver Fire Clay Company (cast-iron crucible and cover, one-quarter gallon, catalog No. 2136). 

Stourbridge hns been tong celebrated fur its fire clay, which is admirably fitted for making crucibles and lining furnaces. The composition of various qua-... 

Low-fired clays differ widely as to their hygroscopic capacity and the temperature at which they release the moisture thus absorbed. At the same time, the expulsion of this moisture requires considerable time. Therefore, it is not sufficient simply to keep the crucibles in a warm place, but they should be finally maintained for at least several days at a higher temperature, say 150 C., before being placed in the furnace. In Europe the crucibles on being taken from this kiln are sometimes covered with a waterproof coat, such as tar or pitch dissolved in turpentine. 

Fire clay Low heat duty High heat duty Mullite, glass, quartz Mullite, glass Up to 1500 Kiln linings Crucibles... 

Hessian cruclbla A cheap, brittle end fregile, but very refractory crucible, composed of the finest fire clay and sand, and commonly uied for a single heating. U is used for essaying, etc. 

The roasted ore is fused with 10 per cent, of its weight of crude argol, or with charcoal or anthracite and potash or soda, in crucibles made of fire-clay, heated in a wind furnace or in a galley furnace. The mould in which the melted metal is cast must be coated with tallow or with a thin layer of fire-clay cream. 

The crucibles were made of fire-clay, and could stand five or six charges each, each charge being 48 5 lbs. of impure antimony. To each charge were added 13 to 17 lbs. of flux, which was a mixture of sulphate and carbonate of soda, with a little salt and pure oxidised antimony ores. The fusion lasted six hours, with a consumption of 450 to 550 lbs. of coal. A low red heat is necessary. 

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