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Venetian Borax: Refining Tincal with Lime

أنشأه

Charlie

13. أكتوبر 2026

Venetian Borax: Refining Tincal with Lime

Native borax, tincal, came to Europe from the dried lake shores of Tibet and India coated in an earthy, soapy fat. Venice, then the Dutch, refined it in secret: the refined salt was called Venetian borax. One of their methods is recorded by Knapp, as Muspratt gives it in 1860: soften the tincal with water and a little slaked lime, wash it clean, dissolve it hot with a little chloride of calcium to take out the last of the soap, then crystallise it in lead-lined wooden cones. Borax is the flux of brazing and soldering.

متوسط

Several days

التعليمات

Weigh the tincal and the additions

Weigh the tincal, about 1 per cent of its weight of slaked lime, and about 2 per cent of chloride of calcium (step 7 works it out for 10 kg).

المواد لهذه الخطوة:

تنكار (بوراكس خام)10 كغ

الجير المطفأ (هيدروكسيد الكالسيوم)100 غ

كلوريد الكالسيوم200 غ

الأدوات المطلوبة:

ميزان ذو كفّتين

Soften it with water and lime

Soften the tincal in a small quantity of cold water in a wooden tub, and stir it about while adding the slaked lime little by little.

المواد لهذه الخطوة:

ماء1 as required

الأدوات المطلوبة:

حوض خشبي

مجداف خشبي

نظارة واقية من رذاذ الكيماويات

قفازات مطاطية

Wash it several times

Pour off the turbid lime-water. Let the impurities settle out of it, then pour the clear liquid back over the crystals. Repeat this several times; it takes away the greater part of the soapy crust.

الأدوات المطلوبة:

حوض خشبي

مجداف خشبي

Dissolve hot with chloride of calcium

Dissolve the washed crystals in hot water and add the chloride of calcium. It turns what soap remains into an insoluble lime soap (and common salt); strain that off.

المواد لهذه الخطوة:

ماء1 as required

فحم نباتي1 as required

الأدوات المطلوبة:

حوض التبخير

فرن فحم

مصفاة

مجداف خشبي

نظارة واقية من رذاذ الكيماويات

قفازات مطاطية

Boil down to 21 degrees Baumé

Evaporate the clear liquid to 21 degrees Baumé, a specific gravity of 1.17, checking with a hydrometer.

المواد لهذه الخطوة:

فحم نباتي1 as required

الأدوات المطلوبة:

حوض التبخير

فرن فحم

مقياس كثافة

Crystallise in lead-lined cones

Run the liquor into wooden vessels lined with lead and shaped as short inverted cones, and let it crystallise. Any deposit collects in the narrow lower part and does not spoil the crystals. Knapp adds that a little tincal stirred in before this last crystallisation keeps the crystals from splitting and flying off the work when heated for soldering.

الأدوات المطلوبة:

خزان التبلور

صفيحة رصاص

Knapp's additions, per 10 kg

جارٍ تحميل دفتر Jupyter…

Powder it for flux

Take out the crystals, dry them and grind them in a mortar to a powder for use as flux. Keep it covered: in dry air borax slowly loses water and turns opaque on the surface.

الأدوات المطلوبة:

هاون ومِدَقّ

Troubleshooting

Borax refining troubleshooting.

Flow

History and honest limits

Muspratt (1860) gives Knapp's two known methods of the secret Venetian and Dutch refining; this is the lime method. The other washed the powdered tincal with caustic soda lye and added carbonate of soda. By Muspratt's time most borax was made instead from the boracic acid of Tuscany and carbonate of soda. Knapp's per cent figures do not say of what; we take them as per cent of the tincal. Grinding the crystals to powder is ours.