Khollan Vafa : اخوان صفا: شب، شب یمانی (صنعا)، مک هندی، زنج زابلی

شب . [ ش َب ب ] (ع اِ) نوعی از زاج باشد و آن را زاج بلور خوانند و گویند که آن از کوه فروچکد و مانند یخ بفسرد و بهترین وی آن است که از جانب یمن آورند و گویند که به این معنی عربی است . (از برهان قاطع). نوعی از زاگ . (آنندراج ) (منتهی الارب ). زاج . نوشادر. (ناظم الاطباء). او را به هندی مک و به زابلی زنج گویند و آن سنگی است که از جوهراو زاک و امثال آن حاصل شود و یمانی بهترین انواع بود و جرم او سفید و مشقوق بود و آنچه جرم او مدور بودنیکوتر بود. (از ترجمه ٔ صیدنه ٔ بیرونی ). معدنی است شبیه به نمک و نوشادر که آن گوگرد آمونیاک و پتاس است بشکل بلور سفید و با مزه ٔ گس . (از متن اللغة). از معدنیاتی است که از نظر شکل و مزه و رنگ دارای شانزده گونه است و بهترین آن شفاف سفید و سخت است که آن را یمانی خوانند زیرا از کوههای صنعا فروریزد و سپس جامد شود و آن را مشقق نیز خوانند و نوع دیگر آن مرطوب و سست و زودشکن باشد. (تذکره ٔ داود ضریر انطاکی ص 314). و از خواص آن در نزد عوام آن است که چون کسی را چشم بد رسد شب را بخور کنند و در آن قطعه سوراخی بصورت چشم ظاهر گردد هرگاه آن را در طرف قبله ٔ خانه ٔ آن شخص گذارند هرگز چشم بد به اهل آن خانه نرسد. (ازتحفه ٔ حکیم مؤمن ). زاغ . زاج . زاک . زمة. زمچ . نک .

- شب ازرق ؛ گوگرد مس است . (از متن اللغة). کات کبود. الشبة الزرقاء.

- شب الاساکفة ؛ قلی مصاعد است . (تحفه ٔ حکیم مؤمن ). و آن را به فارسی کفشکر گویند. (فهرست مخزن الادویه ).

- شب الصباغین ؛قلی است . (تحفه ٔ حکیم مؤمن ).

رجوع به قلی شود.

- شب العصفر ؛ قلی مصاعد است . (تحفه ٔ حکیم مؤمن ).

- شب القلی ؛ قلی مصاعد است . (تحفه ٔ حکیم مؤمن ). قلی مصاعد. (فهرست مخزن الادویه ).

- شب اللیل ؛ نام نباتی است . (از اقرب الموارد). ظاهراً نام گلی باشد.

- شب زفر ؛ نوعی از زاج است مرطوب و زودشکن با بوی زفر و با زهومت . (از تذکره ٔ داود ضریر انطاکی ص 314).

- شب مدحرج ؛ زاج مایل به استداره . (تحفه ٔ حکیم مؤمن ).

- شب مشقق ؛نام نوعی از زاج است . (تذکره ٔ داود ضریر انطاکی ص 314).

- شب منجانی ؛ آن بود که صباغان بکار برند. (از ترجمه ٔ صیدنه ٔ بیرونی ).

|| نوعی از بیماری

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شب‌. انواع بود و آن را زاج بلور گویند از کوه فروچکد و بفسرده مانند یخ آنچه از کوههای یمن خیزد لون آن سفید بود که بزردی مایل بود و قابض بود و در وی حموضتی بود نیکوترین انواع شب آن بود که به یمانی مشهور بود و دیسقوریدوس گوید که انواع شب بسیار بود اما آنچه مستعمل بود در معالجه طبی سه نوع بود مشفف و رطب و مدحرج مشفف یمانی بود و طبیعت وی خشک بود در دویم و سرد بود و گویند گرم و خشک بود در سئوم و گویند گرمی وی در دویم بود چون با دردی سرکه بود نافع بود جهت نزف دم از هر موضع که بود و چون با عسل و سرکه مضمضه کنند دندان متحرک را محکم گرداند و چون با عسل بیامیزند قلاع زایل کند و اگر با عصی الراعی بیامیزند بهق را سود دهد و سیلان ماده که از گوش آید نافع بود و چون با ورق انگور یا ماء العسل بیامیزند جرب ریش‌شده را طلا کنند موافق بود و چون به آب بیامیزند حکه و ریش ناخن و داخس و شقاق که از سرما بود سود دهد و چون یک جزو از وی با یک جزو نمک بیامیزند ریشهای بد که منتشر شده باشد در اعضا نافع بود و چون به آب زفت بر سر مالند سبوسه زایل کند و چون به آب بمالند شپش را بکشد و سوختگی آتش را سودمند بود و بر ورمهای بلغمی لطوخ کردن نافع بود و در شیب بغل مالیدن گند بغل زایل کند و چون اندکی از وی با پشم پاره به فم رحم نهند پیش از جماع مفید بود جهت قطع خون و منع آبستنی و بچه بیرون آورد و جهت ورم لثه و لهاة و وجع اذنین و انثیین بغایت مفید بود و رازی در خواص آن گوید چون در آب تیره اندازند روشن و صافی گرداند در اندک زمان و گویند چون شب در زیر جامه خواب کسی نهند که در خواب بانگ و فریاد کند دیگر نکند و خوردن وی مضر بود تا بحدی که کشنده بود و سرفه سخت پیدا کند و باشد که به سل انجامد و مداوای وی به شیر تازه کنند و قند و مسکه و بدل وی نمک تلخ بود و نمک سیاه بوزن آن.

در مخزن الادویه می‌نویسد: بکسر شین و باء مشدده بفارسی ذمه و زاک سفید و بهندی پهیکری نامند و آن ماهیتی است که مجتمع و منعقد می‌گردد از اجزای اعفنه ارضیه بسبب برودت انعقاد غیر مستحکم یافته از جمله معادن زاجات و املاح و نوشادر و شبوت و آن چیزی است شبیه بزاج با اندک ترشی غلاف زاج که ترشی آن زیاد است.

اختیارات بدیعی، ص: 247

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زاج یا آلوم، ترکیب شیمیایی خاصی است که در کلاسی خاصی از ترکیبات شیمیایی قرار دارد. ترکیب خاصی با فرمول KAl (SO₄)₂.12H₂O است. طبقه وسیع‌تری از ترکیبات شناخته شده به عنوان آلوم‌ها با فرمول AB (SO₄)₂.12H₂O وجود دارد. AB(SO4) 2.12H2O.مقادیر زیادی از آن در یمن موجود می باشد و از رده سنگ های معدنی موجود در بعضی کوه های یمن است، این ماده در عطاری ها موجود بوده و برای اهداف پزشکی و به عنوان ماده ای ضد عرق و برای پاکسازی دندان شناخته می شود و این خواص آن به دلیل مواد سولفات آلومینیوم موجود در آن می باشد.

انواع آلوم[ویرایش]

چهار نوع مختلف از زاج وجود دارد به نام های آلوم آمونیوم, آلوم پتاس, آلوم کروم و آلوم قلیایی

1- آلوم آمونیوم : از نظر شیمیایی, آلوم آمونیوم با فرمول NH4AL(SO4)2.12H2O معرفی می شود. این نوع زاج یک آلومینیوم دو سولفاته است. این گونه از زاج در طبیعت کریستاله و سفید رنگ است.

2- آلوم پتاس : پتاس مربوط به سولفات آلومینیوم پتاسیم می شود و بعنوان یک قابض و ضدعفونی کننده استفاده می گردد. زاج پتاس یک دئودورانت طبیعی است. همچنین زاج پتاس به طور گسترده ای برای تصفیه آب کاربرد دارد. مواد معدنی نظیر کائولینیت و آلونیت, منابع طبیعی تامین زاج پتاس هستند.

3- آلوم کروم : بر خلاف دیگر انواع زاج, این نوع زاج برای فراینده برنزه کردن استفاده می شود. این سولفات دوگانه پتاسیم و کرومیوم با فرمول شیمیایی KCr(SO4)2.12H2O معرفی می شود. این نوع زاج در طبیعت بصورت کریستال بنفش رنگ یافت می گردد.

4- آلوم قلیایی : آلوم قلیایی چیزی جز مندوزیت نیست. نوعی ماده معدنی که در محیط زیست بصورت طبیعی یافت می شود. در تولید نمک مورد استفاده قرار می گیرد. همچنین برای تولید سودا از آن استفاده می شود. آلوم قلیایی همچنین بنام آلوم سدیم نیز شناخته می شود.این نوع زاج با فرمول شیمیایی Na2SO4.Al2(SO4)3.24H2O معرفی می گردد.

منابع[ویرایش]

سایت کیمیا

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الشَبّ^[1][2] أو الشبة^[3] اسم مركب كيميائي يدل أيضا على صنف من المركبات الكيميائية. المركب الكيميائي هو كبريتات البوتاسيوم والألومنيوم المميهة ذوالصيغة KAl(SO₄)₂^.12H₂O.

التصنيف الأوسع للمركبات المعروفة بالشبة لها نفس قياس اتحادية العناصر، ولها الصيغة العامة A₂(SO₄).M2(SO₄)₃.24H₂O، حيث A تمثل كاتيونأحادي التكافؤ مثل البوتاسيوم أو الأمونيوم، وM تمثل أيون فلز ثلاثي التكافؤ مثل الألومنيوم.^[4]

التطبيقات[عدل]

مركبات الشبة مفيدة في مجموعة من العمليات الصناعية. فهي ذوابة في الماء، ولها مذاق حمضي، وقابض (بالإنجليزية: astringent)، مائل إلى الحلاوة، ويتفاعل مع الحموض، ويتبلور وفق جسم مثمن السطوح (octahedron). تتسيل عند تسخينها، وإذا استمر التسخين يمكن استخراج ماء التبلور، تتحول بعدها الأملاح إلى خبث وتنتبج، ويبقى آخر الأمر المسحوق غير البلوري.

شبة البوتاسيوم هي الشبة المتوفرة تجاريا، مع أن هناك أنواعا أخرى تصنع أيضا مثل: شبة الصودا، وشبة الحديد، وشبة الأمونيوم.

وقد يطلق اسم الشبة على كبريتات الألومنيوم في الكلام العامي، ولكن هذا الكلام غير دقيق علميا، فخصائصه مختلفة تماما عن خصائص مركبات الشبة الموصوفة قبلا.

الشب متوفر بكميات كبيرة في اليمن وهو ضمن الأحجار الملحية الطبيعية في بعض جبال اليمن ويعرف باسم شب الفؤاد ويباع أيضا في اسواق البهارات لإزالة العرق وفي الطب الشعبي كعلاج للإمساك وزيادة يؤدي إلى امساك حاد ويستخدم أيضا لتنظيف الأسنان وذلك لوجود الخاصية الحمضية من كبريتات الأمونيوم في المركب وله طعم قابض.

انظر أيضا[عدل]

المراجع[عدل]

^ بحث من كلية الهندسة جامعة بابل
^ «شَبّ: الماهية: قال ديسقوريدوس: أصناف الشبّ كثيرة، والداخل منها في علاج الطب ثلاثة، المشقق والرطب والمدحرج» (ابن سينا. القانون في الطب).
^ المغني الأكبر
^ Austin، George T. (1984). Shreve's Chemical process industries. (الطبعة 5th). New York: McGraw-Hill. صفحة 357. ISBN 9780070571471.

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به آذری زر:

زر KAL (SO4)2.12H2O فورمولویلا بیر خاص کیمیَوی بیرلشمه دیر.

بوگون ایپلیک یادا قوماش(پارچا) بویاما و سو صافلاشدیرمادا چوخ ایشلنیلن زرلرین یئرینی آلومینییوم سولفات آلمیشدیر.
زرلر، سودا راحاتجا حل اولونورلار.
آذربایجان کولتورونده قورخان کیمسه، قورخوسو تؤکولوب و اورگی ییغیشسین دئیه نئچه زر تکه سی اوتار.

قایناق[دَییشدیر]

معدنی داش تانیلان زرلر، یمن داغ لاریندا چوخ تاپیلیر و طب یا توختادمادا، تَر آزالتما و دیش تمیزلمه آماجییلا ایشلنیلیر.

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به اردو زاج:

پھٹکڑی (alum) جس کو عام طور پر پھٹکری بھی کہا جاتا ہے ایک آبیدہ اُشنانصر زاصر سلفیٹ (hydrated potassium aluminium sulfate) کیمیائی مرکب ہے جس کا کیمیائی صیغہ، K Al(SO₄)₂^.12H₂O ، اختیار کیا جاتا ہے۔

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به عبری آلوم/آلم:

אלום (אנגלית: Alum‏, IPA‏: /ˈæləm/) הוא מונח המתייחס לתרכובת כימית ספציפית וקבוצה של תרכובות כימיות. התרכובת הספציפית היא הידרט-אלומיניום-אשלגן-סולפט, ונוסחתה הכימית היא KAl(SO₄)₂^.12H₂O. לקבוצת התרכובות יש מבנה סטויכיומטרייחסי של AB(SO₄)₂^.12H₂O.

לתרכובות אלום יש מגוון שימושים בתעשייה ובמסחר כגון איפור וייצור חומרים חסיני אש. הוא משמש כחומר מכווץ וממלא בתעשיית עיבוד עור לקלף הראוי לכתיבה והנקרא נייר פרגמנט.

האלום שימש בתהליך צביעת צמר בעולם העתיק: החומר משמש כצרבן המקשר בין הצבע הטבעי (בעיקר מן החי) לבין הצמר.

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به ترکی شب:

Şap (bileşik)

Başlığın diğer anlamları için Şap (anlam ayrımı) sayfasına bakınız.

Şaplar çift tuz grubuna giren bileşiklerdir. Genel formülleri [Me⁺¹Me⁺³(SO₄)2.12H₂O] şeklindedir. Buradaki Me⁺¹ = K⁺, NH₄+, Rb⁺, Cs⁺, TI⁺;Me⁺³ = Al⁺³, Fe⁺³, Ga⁺³, In⁺³, Cr⁺³, V⁺³ şeklinde ifade edilebilir.

İplik ya da kumaş boyama ve su saflaştırmada sıkça kullanılan şapların yerini bugün alüminyum sülfat almıştır.

Şaplar, suda kolayca çözünürler ve tatlımsı bir tada sahiptirler.

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Alum /ˈæləm/ is both a specific chemical compound and a class of chemical compounds. The specific compound is the hydrated potassium aluminium sulfate (potassium alum) with the formula K Al(SO
4)₂·12H
2O. More widely, alums are double sulfate salts, with the general formulaA
2(SO
4).M
2(SO
4)
3.24H
2O, where A is a monovalent cation such as potassium or ammonium and M is atrivalent metal ion such as aluminium or chromium(III).^[1] When the trivalent ion is aluminium, the alum is named after the monovalent ion.

Contents

[show]

Chemical properties[edit]

Alums are useful for a range of industrial processes. They are soluble in water; have a sweetish taste; reactacid to litmus; and crystallize in regular octahedra. When heated they liquefy; and if the heating is continued, the water of crystallization is driven off, the salt froths and swells, and at last an amorphous powder remains. They are astringent and acidic.

Uses[edit]

Industrial uses[edit]

Potassium alum is the common alum of commerce, although soda alum, ferric alum, and ammonium alum are manufactured.

Alum has been used at least since Roman times for purification of drinking water^[2] and industrial process water. Between 30 and 40 ppm of alum^[2][3] for household wastewater, often more for industrial wastewater,^[4] is added to the water so that the negatively charged colloidal particles clump together into "flocs", which then float to the top of the liquid, settle to the bottom of the liquid, or can be more easily filtered from the liquid, prior to further filtration and disinfection of the water.

Alum solution has the property of dissolving steels while not affecting aluminium or base metals, and can be used to recover workpieces made in these metals with broken toolbits^[5] lodged inside them.^[6] As considerable expense and/or effort may have gone into machining a specialist part, this can be a worthwhile exercise.

Cosmetic[edit]

An alum block sold as an astringentin pharmacies in India (where it is widely known as Fitkari )^[7]

Alum in block form (usually potassium alum) can be used as a blood coagulant.^[8]
Styptic pencils containing aluminium sulfate or potassium aluminium sulfate are used as astringents to prevent bleeding from small shaving cuts.
Alum may be used in depilatory waxes used for the removal of body hair or applied to freshly waxed skin as a soothing agent.
In the 1950s, men sporting crewcut or flattop hairstyles sometimes applied alum to their hair as an alternative topomade^{[citation needed]}. When the hair dried, it would stay up all day.
Alum's antiperspirant and antibacterial properties^[9][10] contribute to its traditional use as an underarmdeodorant.^[11] It has been used for this purpose in Europe, Mexico, Thailand (where it is called sarn-som), throughout Asia and in the Philippines (where it is called tawas). Today, potassium or ammonium alum is sold commercially for this purpose as a "deodorant crystal", often in a protective plastic case.^[12]

Culinary[edit]

Alum powder, found in the spice section of many grocery stores, may be used in pickling recipes as a preservative to maintain fruit and vegetable crispness.
Alum is used as the acidic component of some commercial baking powders.
Alum was used by bakers in England during the 1800s to make bread whiter. This was thought by some, without adequate scientific grounds, to causerickets.^[13][14] The Sale of Food and Drugs Act 1875 prevented this and other adulterations.^[15]

Flame retardant[edit]

Solutions containing alum may be used to treat cloth, wood, and paper materials to increase their resistance to fire.
Alum is also used in fire extinguishers to smother chemical and oil fires.^{[citation needed]}

Chemical flocculant[edit]

Alum is used to clarify water by neutralizing the electrical double layer surrounding very fine suspended particles, allowing them to flocculate (stick together). After flocculation, the particles will be large enough to settle and can be removed.
Alum may be used to increase the viscosity of a ceramic glaze suspension; this makes the glaze more readily adherent and slows its rate ofsedimentation.

Taxidermy[edit]

Alum is used in the tanning of animal hides to remove moisture, prevent rotting, and produce a type of leather.^{[citation needed]} Traditionally treating hides with alum, instead of tannic acid, is called tawing and not tanning. The product is traditionally called parchment instead of leather.

Medicine[edit]

Alum is used in the treatment of canker sores in the mouth, as it has a significant drying effect to the area and reduces the irritation felt at the site.
Alum is the major adjuvant used to increase the efficacy of vaccines, and has been used since the 1920s.^[16][17]
Alum has been used to stop bleeding in cases of hemorrhagic cystitis.^[18]

Art[edit]

Alum is used to fix pigments on a surface, for example in paper marbling.^{[citation needed]}
Alum is an ingredient in some recipes for homemade modeling compounds intended for use by children. These are often called "play clay" or "play dough" for their similarity to "Play-Doh".^{[citation needed]}

History[edit]

In antiquity[edit]

The word 'alumen' occurs in Pliny's Natural History. In the 52nd chapter of his 35th book, he gives a detailed description.^[11] By comparing this with the account of 'stupteria' given by Dioscorides in the 123rd chapter of his 5th book, it is obvious the two are identical. Pliny informs us that 'alumen' was found naturally in the earth. He calls it 'salsugoterrae'. Different substances were distinguished by the name of 'alumen', but they were all characterised by a certain degree of astringency, and were all employed in dyeing and medicine, the light-colored alumen being useful in brilliant dyes, the dark-colored only in dyeing black or very dark colors.^[11] One species was a liquid, which was apt to be adulterated; but when pure it had the property of blackening when added to pomegranate juice. This property seems to characterize a solution of iron sulfate in water; a solution of ordinary (potassium) alum would possess no such property. Pliny says that there is another kind of alum that the Greeks call 'schiston', and which "splits into filaments of a whitish colour",^[11] From the name 'schiston' and the mode of formation, it appears that this species was the salt that forms spontaneously on certain salty minerals, as alum slate and bituminous shale, and consists chiefly of sulfates of iron and aluminium.^{[citation needed]} In some places the iron sulfate may have been lacking, so the salt would be white and would answer, as Pliny says it did, for dyeing bright colors. Pliny describes several other species of alumen but it is not clear as to what these minerals are.

The alumen of the ancients then, was not always the same as the alum of the moderns. They knew how to produce alum from alunite, as this process is archaeologically attested on the island Lesbos.^[19] This site was abandoned in the 7th century but dates back at least to the 2nd century CE. Native alumen from Melos appears to have been a mixture mainly of alunogen (Al
2(SO
4)
3·17H
2O) with alum and other minor sulfates.^[20] The western desert of Egypt was a major source of alum substitutes in antiquity. These evaporites were mainly FeAl
2(SO
4)
4·22H
2O, MgAl
2(SO
4)
4·22H
2O, NaAl(SO
4)
2·6H
2O, MgSO
4·7H
2Oand Al
2(SO
4)
3·17H
2O.^[21] Contamination with iron sulfate was greatly disliked as this darkened and dulled dye colours. They were acquainted with a variety of substances of varying degrees of purity by the names of misy, sory, and chalcanthum. As alum and green vitriol were applied to a variety of substances in common, and as both are distinguished by a sweetish and astringent taste, writers, even after the discovery of alum, do not seem to have discriminated the two salts accurately from each other. In the writings of the alchemists we find the words misy, sory, chalcanthum applied to alum as well as to iron sulfate; and the name atramentum sutorium, which one might expect to belong exclusively to green vitriol, applied indifferently to both. Various minerals are employed in the manufacture of alum, the most important being alunite, alum schist, bauxite and cryolite.

Alchemical and later discoveries and uses[edit]

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In the 18th century, J. H. Pott and Andreas Sigismund Marggraf demonstrated that alumina was a constituent. Pott in his Lithogeognosia showed that theprecipitate obtained when an alkali is poured into a solution of alum is quite different from lime and chalk, with which it had been confounded by G.E. Stahl. Marggraf showed that alumina is one of the constituents of alum, but that this earth possesses peculiar properties, and is one of the ingredients in commonclay. He also showed that crystals of alum can be obtained by dissolving alumina in sulfuric acid and evaporating the solutions, and when a solution ofpotash or ammonia is dropped into this liquid, it immediately deposits perfect crystals of alum.

Torbern Bergman also observed that the addition of potash or ammonia made the solution of alumina in sulfuric acid crystallize, but that the same effect was not produced by the addition of soda or of lime, and that potassium sulfate is frequently found in alum.

After M.H. Klaproth had discovered the presence of potassium in leucite and lepidolite, it occurred to L. N. Vauquelin that it was probably an ingredient likewise in many other minerals. Knowing that alum cannot be obtained in crystals without the addition of potash, he began to suspect that this alkali constituted an essential ingredient in the salt, and in 1797 he published a dissertation demonstrating that alum is a double salt, composed of sulfuric acid, alumina, and potash. Soon after, J.A. Chaptal published the analysis of four different kinds of alum, namely, Roman alum, Levant alum, British alum and alum manufactured by himself. This analysis led to the same result as Vauquelin.

Early uses in industry[edit]

Egyptians reportedly used the coagulant alum as early as 1500 BC to reduce the visible cloudiness (turbidity) in the water. Alum was imported into England mainly from the Middle East, and, from the late 15th century onwards, the Papal States for hundreds of years. Its use there was as a dye-fixer (mordant) forwool (which was one of England's primary industries, the value of which increased significantly if dyed). These sources were unreliable, however, and there was a push to develop a source in England especially as imports from the Papal States were ceased following the excommunication of Henry VIII.^{[citation needed]}

In the 13th and 14th centuries, alum (from alunite) was a major import from Phocaea (Gulf of Smyrna in Byzantium) by Genoans and Venetians (and was a cause of war between Genoa and Venice) and later by Florence. After the fall of Constantinople, alunite (the source of alum) was discovered at Tolfa in the Papal States (1461). The textile dyeing industry in Bruge, and many other locations in Italy, and later in England, required alum to stabilize the dyes onto the fabric (make the dyes "fast") and also to brighten the colors.^[22][23][24]

With state financing, attempts were made throughout the 16th century, but without success until early on in the 17th century. An industry was founded inYorkshire to process the shale, which contained the key ingredient, aluminium sulfate, and made an important contribution to the Industrial Revolution. One of the oldest historic sites for the production of alum from shale and human urine are the Peak alum works in Ravenscar, North Yorkshire. By the 18th century, the landscape of northeast Yorkshire had been devastated by this process, which involved constructing 100 feet (30 m) stacks of burning shale and fuelling them with firewood continuously for months. The rest of the production process consisted of quarrying, extraction, steeping of shale ash with seaweed in urine, boiling, evaporating, crystallisation, milling and loading into sacks for export. Quarrying ate into the cliffs of the area, the forests were felled for charcoal and the land polluted by sulfuric acid and ash.^[25]

Production[edit]

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From alunite[edit]

In order to obtain alum from alunite, it is calcined and then exposed to the action of air for a considerable time. During this exposure it is kept continually moistened with water, so that it ultimately falls to a very fine powder. This powder is then lixiviated with hot water, the liquor decanted, and the alum allowed to crystallize. The alum schists employed in the manufacture of alum are mixtures of iron pyrite, aluminium silicate and various bituminous substances, and are found in upper Bavaria, Bohemia, Belgium, and Scotland. These are either roasted or exposed to the weathering action of the air. In the roasting process, sulfuric acid is formed and acts on the clay to form aluminium sulfate, a similar condition of affairs being produced during weathering. The mass is now systematically extracted with water, and a solution of aluminium sulfate of specific gravity 1.16 is prepared. This solution is allowed to stand for some time (in order that any calcium sulfate and basic ferric sulfate may separate), and is then evaporated until ferrous sulfate crystallizes on cooling; it is then drawn off and evaporated until it attains a specific gravity of 1.40. It is now allowed to stand for some time, decanted from any sediment, and finally mixed with the calculated quantity of potassium sulfate, well agitated, and the alum is thrown down as a finely divided precipitate of alum meal. If much iron should be present in the shale then it is preferable to use potassium chloride in place of potassium sulfate.

From clays or bauxite[edit]

In the preparation of alum from clays or from bauxite, the material is gently calcined, then mixed with sulfuric acid and heated gradually to boiling; it is allowed to stand for some time, the clear solution drawn off and mixed with acid potassium sulfate and allowed to crystallize. When cryolite is used for the preparation of alum, it is mixed with calcium carbonate and heated. By this means, sodium aluminate is formed; it is then extracted with water andprecipitated either by sodium bicarbonate or by passing a current of carbon dioxide through the solution. The precipitate is then dissolved in sulfuric acid, the requisite amount of potassium sulfate added and the solution allowed to crystallize.

Types[edit]

Many trivalent metals are capable of forming alums. The general form of an alum is AM^III(SO₄)₂·nH₂O, where A is an alkali metal or ammonium, M^III is a trivalent metal, and n often is 12. In general, alums are easier formed when the alkali metal atom is larger. This rule was first stated by Locke in 1902,^[26]who found that if a trivalent metal does not form a caesium alum, it neither will form an alum with any other alkali metal or with ammonium.

Double sulfates with the general formula A
2SO
4·B
2(SO
4)
3·24H
2O, are known where A is a monovalent cation such as sodium, potassium, rubidium,caesium, or thallium(I), or a compound cation such as ammonium (NH+
4), methylammonium (CH
3NH+
3), hydroxylammonium (HONH+
3) or hydrazinium(N
2H+
5), B is a trivalent metal ion, such as aluminium, chromium, titanium, manganese, vanadium, iron(III), cobalt(III), gallium, molybdenum, indium,ruthenium, rhodium, or iridium.^[27] Analogous selenates also occur. The specific combinations of univalent cation, trivalent cation, and anion depends on the sizes of the ions. For example, unlike the other alkali metals the smallest one, lithium, does not form alums, and there is only one known sodium alum. In some cases, solid solutions of alums occur.

Alums crystallize in one of three different crystal structures. These classes are called α-, β- and γ-alums.

Potash alum[edit]

Crystal of potassium alum

Main article: Potassium alum

Aluminum potassium sulfate, potash alum, KAl(SO
4)
2·12H
2O is used as an astringent and antisepsis in various food preparation processes such as pickling and fermentation and as a flocculant for water purification, among other things. A common method of producing potash alum is leaching of alumina from bauxite, which is then reacted withpotassium sulfate. As a naturally occurring mineral, potash alum is known as alum-(K). Other potassium aluminium sulfate minerals are alunite (KAl(SO
4)
2·2Al(OH)
3) and kalinite (KAl(SO
4)
2·11H
2O).

Soda alum[edit]

Main article: Sodium aluminium sulfate

Soda alum, NaAl(SO
4)
2·12H
2O, mainly occurs in nature as the mineral mendozite. It is very soluble in water, and is extremely difficult to purify. In the preparation of this salt, it is preferable to mix the component solutions in the cold, and to evaporate them at a temperature not exceeding 60 °C. 100 parts of water dissolve 110 parts of sodium alum at 0 °C, and 51 parts at 16 °C. Soda alum is used in the acidulent of food as well as in the manufacture of baking powder.

Ammonium alum[edit]

Main article: Ammonium aluminium sulfate

Ammonium alum, NH
4Al(SO
4)
2·12H
2O, a white crystalline double sulfate of aluminium, is used in water purification, in vegetable glues, in porcelain cements, in deodorants (though potassium alum is more commonly used), in tanning, dyeing and in fireproofing textiles.

Chrome alum[edit]

Alum crystal with small amount ofchrome alum to give a slight violet color

Main article: Chrome alum

Chrome alum, KCr(SO
4)
2·12H
2O, a dark violet crystalline double sulfate of chromium and potassium, was used intanning.

Selenate-containing alums[edit]

Alums are also known that contain selenium in place of sulfur in the sulfate anion, making selenate (SeO2−
4) instead. They are called selenium- or selenate-alums. They are strong oxidizing agents.

Aluminium sulfate[edit]

Main article: Aluminium sulfate

Aluminium sulfate is referred to as papermaker's alum. Although reference to this compound as alum is quite common in industrial communication, it is not regarded as technically correct. Its properties are quite different from those of the set of alums described above. Most industrial flocculation done with alum is actually aluminium sulfate.

Solubility[edit]

The solubility of the various alums in water varies greatly, sodium alum being readily soluble in water, while caesium and rubidium alums are only sparingly soluble. The various solubilities are shown in the following table.

At temperature T, 100 parts water dissolve:

T	Ammonium alum	Potassium alum	Rubidium alum	Cesium alum
0 °C	2.62	3.90	0.71	0.19
10 °C	4.50	9.52	1.09	0.29
50 °C	15.9	44.11	4.98	1.235
80 °C	35.20	134.47	21.60	5.29
100 °C	70.83	357.48

Related compounds[edit]

In addition to the alums, which are dodecahydrates, double sulfates and selenates of univalent and trivalent cations occur with other degrees of hydration. These materials may also be referred to as alums, including the undecahydrates such as mendozite and kalinite, hexahydrates such as guanidinium(CH
6N+
3) and dimethylammonium ((CH
3)
2NH+
2) "alums", tetrahydrates such as goldichite, monohydrates such as thallium plutonium sulfate and anhydrous alums (yavapaiites). These classes include differing, but overlapping, combinations of ions.

A pseudo alum is a double sulfate of the typical formula ASO
4·B
2(SO
4)
3·22H
2O, where A is a divalent metal ion, such as cobalt (wupatkiite), manganese(apjohnite), magnesium (pickingerite) or iron (halotrichite or feather alum), and B is a trivalent metal ion.^[28]

A Tutton salt is a double sulfate of the typical formula A
2SO
4·BSO
4·6H
2O, where A is a univalent cation, and B a divalent metal ion.

Double sulfates of the composition A
2SO
4·2BSO
4, where A is a univalent cation and B is a divalent metal ion are referred to as langbeinites, after the prototypical potassium magnesium sulfate.

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