Aluminium Hydroxide: Alum Solution Dropped into Ammonia Water (Ure 1839)

Drop a weak alum solution into ammonia water and a bulky white precipitate falls: aluminium hydroxide, which Ure called aluminous earth. Washed, it is the starting point for aluminium salts and for alumina. Result: a bulky white precipitate; dried, it weighs 10.82 % of the alum used. Ure dissolves it in acid while it is still moist. Source: Ure, Dictionary of Arts, Manufactures, and Mines (1839), Alum. Not given: how much ammonia water, its strength, how it is washed. Ours: work in fresh air, as ammonia fumes sting. Picture drawn by Youblob.

مبتدئ

3 hours

التعليمات

Dissolve alum in 20 parts of water

Weigh the alum and dissolve it in 20 times its weight of water.

المواد لهذه الخطوة:

شبّة (شبّ البوتاسيوم)1 part by weight

الأدوات المطلوبة:

ماء مقطر

ميزان ذو كفّتين

كأس زجاج بوروسيليكاتي

قضيب تحريك زجاجي

Drop it slowly into ammonia water

Drop the alum solution slowly into caustic ammonia water, stirring, until the ammonia is nearly, but not entirely, saturated. A bulky white precipitate falls down. Ure gives no strength. Ours: 25-28 % ammonia solution.

الأدوات المطلوبة:

محلول نشادر 25-28 %

كأس زجاج بوروسيليكاتي

قضيب تحريك زجاجي

Wash the precipitate with water

Wash the precipitate properly with water. Ure does not say how. Ours: collect it on filter paper in a funnel and pour water through until the washings no longer smell of ammonia.

الأدوات المطلوبة:

قمع زجاجي ذو ساق

ورق ترشيح

ماء مقطر

Keep it moist for dissolving

Dried, the precipitate weighs 10.82 % of the alum. Ure dissolves it in acid while it is still moist. Ours: keep it wet in a closed jar until it is used.

الأدوات المطلوبة: