Gold number: Difference between revisions
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{{Short description|Concept in chemistry}} |
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{{orphan|date=August 2009}} |
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{{distinguish|Gold code}} |
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The '''gold number''' is the minimum weight (in milligrams) of a [[protective colloid/lyophilic colloid]] required to prevent the coagulation of 10 ml of a standard hydro [[gold]] [[Sol (colloid)|sol]] when 1 ml of a 10% [[sodium chloride]] solution is added to it.<ref>{{Cite book |last=Hadkar |first=Dr U. B. |url=https://books.google.com/books?id=V3VIaBDTpJ8C |title=Physical Pharmacy |date= |publisher=Nirali Prakashan |isbn=978-81-85790-34-3 |language=en}}</ref> It was first used by [[Richard Adolf Zsigmondy]] in 1901. |
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An [[electrical double layer]] is normally present on the gold sol particles, resulting in electrostatic repulsion between the particles. The sodium chloride ions disrupt this electrical double layer, causing coagulation to occur. |
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'''Gold number''' is a term used in [[colloidal chemistry]]. It is defined as the minimum amount of [[lyophilic colloid]] in milligrams which prevents the [[flocculation]] [[Colloid#Destabilizing a colloidal dispersion (flocculation)]] against 1 ml of 10%NaCl solution. |
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The coagulation of gold sol results in an increase in [[particle size]], indicated by a colour change from red to blue or purple. The higher the gold number, the lower the protective power of the colloid, because a greater amount of colloid is required to prevent coagulation. |
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The gold number of some [[colloid]]s |
The gold number of some [[colloid]]s are given below. |
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<gallery> |
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</gallery> |
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{| class="wikitable" border="1" |
{| class="wikitable" border="1" |
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|- |
|- |
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! Protective |
! Protective Colloid |
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! Gold Number |
! Gold Number |
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| [[Potato starch|Potato Starch]] |
| [[Potato starch|Potato Starch]] |
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| 25 |
| 20-25 |
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|- |
|- |
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| [[Gum arabic]] |
| [[Gum arabic]] |
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| 0.15-0.25 |
| 0.15-0.25 |
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|- |
|- |
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| [[Caseinate]] |
| [[Caseinate]] |
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| 0.01 |
| 0.01-0.02 |
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|- |
|- |
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| [[Sodium oleate|Sodium Oleate]] |
| [[Sodium oleate|Sodium Oleate]] |
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| Line 36: | Line 36: | ||
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|- |
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| [[Dextrin]] |
| [[Dextrin]] |
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| 125-150 |
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|- |
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|} |
|} |
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==References== |
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{{Reflist}} |
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{{DEFAULTSORT:Gold Number}} |
{{DEFAULTSORT:Gold Number}} |
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[[Category:Colloidal chemistry]] |
[[Category:Colloidal chemistry]] |
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Latest revision as of 09:14, 7 October 2024
The gold number is the minimum weight (in milligrams) of a protective colloid/lyophilic colloid required to prevent the coagulation of 10 ml of a standard hydro gold sol when 1 ml of a 10% sodium chloride solution is added to it.[1] It was first used by Richard Adolf Zsigmondy in 1901.
An electrical double layer is normally present on the gold sol particles, resulting in electrostatic repulsion between the particles. The sodium chloride ions disrupt this electrical double layer, causing coagulation to occur.
The coagulation of gold sol results in an increase in particle size, indicated by a colour change from red to blue or purple. The higher the gold number, the lower the protective power of the colloid, because a greater amount of colloid is required to prevent coagulation.
The gold number of some colloids are given below.
| Protective Colloid | Gold Number |
|---|---|
| Gelatin | 0.005-.01 |
| Haemoglobin | 0.03-0.07 |
| Egg Albumin | 0.15-0.25 |
| Potato Starch | 20-25 |
| Gum arabic | 0.15-0.25 |
| Caseinate | 0.01-0.02 |
| Sodium Oleate | 1-5 |
| Dextrin | 125-150 |
References
[edit]- ^ Hadkar, Dr U. B. Physical Pharmacy. Nirali Prakashan. ISBN 978-81-85790-34-3.