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Alumina: Alum Precipitated with Water of Ammonia and Calcined, Ure 1839
Aariuser I (Wikimedia Commons) · CC BY-SA 2.0
Charlie

Created by

Charlie

14. October 2026DE
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Alumina: Alum Precipitated with Water of Ammonia and Calcined, Ure 1839

Alum is the earth of clay, alumina, joined to sulphuric acid and potash. Andrew Ure (1839): drop a weak alum solution into water of ammonia and a bulky white earth falls; washed, it is pure alumina hydrate. Calcined hot, it gives up its water and leaves alumina. Strong ammonia stings the eyes and lungs: work in the open with goggles. The picture: aluminium oxide on a watch glass.
Intermediate
Three days

Instructions

1

Dissolve the alum

Dissolve the alum in twenty times its weight of water (step 5).

Materials for this step:

Alum (Potassium Alum)Alum (Potassium Alum)500 g

Tools needed:

Distilled WaterDistilled Water
Balance ScaleBalance Scale
Large Cooking PotLarge Cooking Pot
Glass Stirring RodGlass Stirring Rod
2

Precipitate

Outdoors, drop the alum solution slowly into water of ammonia, stirring, until the ammonia is nearly but not quite used up (red litmus barely turns blue). A bulky white earth falls.

Tools needed:

Ammonia Solution - 25-28%Ammonia Solution - 25-28%
Borosilicate BeakerBorosilicate Beaker
Glass Stirring RodGlass Stirring Rod
Litmus PaperLitmus Paper
Chemical Splash GogglesChemical Splash Goggles
Rubber GlovesRubber Gloves
3

Wash and dry

Let it settle, pour off the liquid, and wash the earth several times with clean water on a cloth. Dry it.

Tools needed:

Cloth (Straining)Cloth (Straining)
Distilled WaterDistilled Water
Large Cooking PotLarge Cooking Pot
Chemical Splash GogglesChemical Splash Goggles
Rubber GlovesRubber Gloves
4

Calcine

Pack the dry earth in a fireclay crucible and heat it in the furnace to about 1000 °C, checked with the pyrometer, for some hours. Cool, grind and keep the white alumina in a closed jar.

Tools needed:

Clay Crucible - RefractoryClay Crucible - Refractory
Charcoal FurnaceCharcoal Furnace
CharcoalCharcoal
PyrometerPyrometer
Crucible TongsCrucible Tongs
Welding GlovesWelding Gloves
Mortar and PestleMortar and Pestle
Glass JarGlass Jar
5

Earth from your alum

Loading Jupyter Notebook...

Materials

1

Tools Required

18

This blueprint makes

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Alumina Powder (Aluminium Oxide)

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Water of Ammonia from Sal Ammoniac and Lime, Ure 1839
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Water of Ammonia from Sal Ammoniac and Lime, Ure 1839

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