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Glass Pipettes: Tube Drawn to a Tip, Graduated by Weighing Water

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Bubbles

14. أكتوبر 2026

Glass Pipettes: Tube Drawn to a Tip, Graduated by Weighing Water

A pipette is a straight glass tube drawn to a narrow tip: dip it in, close the top with a finger, and let out just the volume you want. Drawn and left plain it is a simple transfer pipette; marked along its length it is a graduated pipette, and a Mohr pipette starts its marks well above the tip and is read as it drains. The picture: our diagram of a plain and a graduated (Mohr) pipette.

متوسط

Half an hour per pipette

التعليمات

Draw the tip

Heat a band of straight, even tube while turning, take it out and pull a short taper, as for a capillary. Cut it at the taper to leave a tip about 1 mm across.

المواد لهذه الخطوة:

طقم أنابيب زجاجية1 قطعة

الأدوات المطلوبة:

شعلة نفخ زجاج طاولية

مِخطّ ماسي

نظارات أمان

قفّازات مقاومة للحرارة

Finish both ends

Fire-polish the tip lightly without closing it, and fire-polish the top so a finger seals it well.

الأدوات المطلوبة:

شعلة نفخ زجاج طاولية

مبارد (مبرد يدوي)

Graduate it (Mohr)

Fill above the top mark, let it drain into a weighed beaker on the balance, stopping each few grams and scratching a line at the level. Keep the first mark well above the tip.

المواد لهذه الخطوة:

ماء0.2 لتر

الأدوات المطلوبة:

ميزان ذو كفّتين

كأس زجاجي مدرّج

مِخطّ ماسي

مسطرة

Mark spacing

جارٍ تحميل دفتر Jupyter…

Use

Hold it upright, tip in the liquid but off the bottom; draw liquid up with a bulb (never by mouth), close the top with your forefinger and let it down to the mark.