# pH adjusters for cosmetics السلام عليكم احتاج ماده تحافظ علي درجه ال pH لحمام الكريم 5 ؟؟؟



## الكيميائي86 (29 أغسطس 2014)

السلام عليكم احتاج مادة كيميائيه او طبيعيه للحفاظ علي درجه ال pH لتكون 5 ...... و من لديه معلومات اكثر عن المواد التي تستخدم في حفظ درجه الاس الهيدروجيني في مستحضرات التجميل ارجو ان يشرح الموضوع لي اكثر ...... اريد عدة مراجع عن مستحضرات التجميل حيث اني ساستلم العمل غدا و انا ليس لي سابق خبره ... ارجو ان تساعدوني في معرفه الاختبارات و الكيمياويات الضرورية و اماكن شرائها في مصر .؟؟؟


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## عبدالقادر2 (30 أغسطس 2014)

استخدام buffer يفيد وكل نوع منه يثبت الph عند قيمه محدده وهذه المحاليل تتكون من حمض ضعيف واحد املاحة مثل الاسيتيك او السيتريك او الفوسفوريك ممكن حضرتك تبحث عن من منهم يثبت القيمه عند 5وتستخدمه


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## عبدالقادر2 (30 أغسطس 2014)

على سبيل المثال 48.5ملى من محلول 1مولار من حامض السيتريك مضاف الى 51.5ملى من محلول 2مولار من ملح ثنائى صوديوم الفوسفات يصنع محلول مثبت عند القيمه 5 . وحمض السيتريك واملاحة يثبت القيمة بين 3.8-5.8 وهكذا يمكنك البحث والاختيار والاضافة تكون على المنتج بنسبة صغيرة مثل المواد الحافظه


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## 83moris (30 أغسطس 2014)

ارجو المقال الاتي يفيدك:
*What is a buffer solution?*
*Definition *
A buffer solution is one which resists changes in pH when small quantities of an acid or an alkali are added to it.
*Acidic buffer solutions*
An acidic buffer solution is simply one which has a pH less than 7. Acidic buffer solutions are commonly made from a weak acid and one of its salts - often a sodium salt.
A common example would be a mixture of ethanoic acid and sodium ethanoate in solution. In this case, if the solution contained equal molar concentrations of both the acid and the salt, it would have a pH of 4.76. It wouldn't matter what the concentrations were, as long as they were the same.
You can change the pH of the buffer solution by changing the ratio of acid to salt, or by choosing a different acid and one of its salts.

*Alkaline buffer solutions*
An alkaline buffer solution has a pH greater than 7. Alkaline buffer solutions are commonly made from a weak base and one of its salts.
A frequently used example is a mixture of ammonia solution and ammonium chloride solution. If these were mixed in equal molar proportions, the solution would have a pH of 9.25. Again, it doesn't matter what concentrations you choose as long as they are the same.

*How do buffer solutions work?*
A buffer solution has to contain things which will remove any hydrogen ions or hydroxide ions that you might add to it - otherwise the pH will change. Acidic and alkaline buffer solutions achieve this in different ways.
*Acidic buffer solutions*
We'll take a mixture of ethanoic acid and sodium ethanoate as typical.
Ethanoic acid is a weak acid, and the position of this equilibrium will be well to the left
+CH3COOH --><----- CH3COO-+H
Adding sodium ethanoate to this adds lots of extra ethanoate ions. According to Le Chatelier's Principle, that will tip the position of the equilibrium even further to the left.


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## 83moris (30 أغسطس 2014)

The solution will therefore contain these important things:


lots of un-ionised ethanoic acid;
lots of ethanoate ions from the sodium ethanoate;
enough hydrogen ions to make the solution acidic.
Other things (like water and sodium ions) which are present aren't important to the argument.
*Adding an acid to this buffer solution*
The buffer solution must remove most of the new hydrogen ions otherwise the pH would drop markedly.
Hydrogen ions combine with the ethanoate ions to make ethanoic acid. Although the reaction is reversible, since the ethanoic acid is a weak acid, most of the new hydrogen ions are removed in this way.
CH3COO-+H+--------><---CH3COOH
Since most of the new hydrogen ions are removed, the pH won't change very much - but because of the equilibria involved, it _will_ fall a little bit.


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## wael_QWE (8 أكتوبر 2014)

استغفرك ربي و اتوب اليك اني كنت من الظالمين


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