كلوريد الحديديك (مواصفاته/تحضيره/استخداماته)

The chemistry of ferric chloride

by

general.dr

bahaa badr

technolab el-bahaa group

Since Rembrandt, etchers have used nitric acid and Dutch mordant to etch copper.

At the turn of the century ferric chloride solution was introduced in gravure work, principally because of its interaction with gum bichromated gelatine.

With the increased emphasis on health and safety at work, we have had to reappraise these and the other chemicals we use.

The salt, ferric chloride, has none of the disadvantages associated with the other two acid etching solutions: it does not produce dangerous fumes, is odourless and, though corrosive, is not absorbed through the skin.

Ferric chloride solutions in water are strong acidic but in their reaction with copper no significant fumes or gases are produced.

Simply, except in the presence of free oxygen, copper will not react to any significant extent with hydrochloric acid which is the acid produced with ferric chloride solutions.

The chemistry of the (etching) reaction

When ferric chloride is dissolved in water the solution becomes strongly acidic as a result of hydrolysis. The chemical reactions, in words and formulae are:

Schematic representation of the chemical interactions occurring during etching copper in ferric chloridesolution.

basically, ferric chloride in water solution ionises to iron (ferric) and chloride ions;

whilst the water ionises to hydrogen and hydroxyl ions;

The ferric ions will partially combine with the hydroxide ions to form ferric hydroxide, a compound which is only slightly soluble and precipitates from solution as a brown solid.

This precipitation can be regarded as removing hydroxyl ions from the solu-tion, leaving a relative excess of hydro-gen ions and it is this excess that makes the solution acidic.

Because of a property of metals known as electro-negativity, copper replace iron from the solution and form a mixture of ferrous and cupric ions. Effectively the copper dissolves without producing any gas;

Ferrous ions become increasingly stable as the solution becomes more acidic and this helps the copper dis-solution to proceed more easily whilst in basic (less acidic) solutions the ten-dency is for ferrous ions to convert back to ferric.

As more copper dissolves and the solubility limit is exceeded, cupric chloride precipitates from the solution, as anything from a green to a blue solid.

Strengths and mixing

Ferric chloride can be obtained either as a solid (not recommended as it can give off highly toxic hydrogen chloride fumes when mixed with water) or in liquid form when it is usually supplied in a strength of 45º Baume.

This mea-surement equates to a specific gravity of approximately 1.43 or a weight to volume ratio of 39-41%. Purveyors of ferric chloride can use any of these measure-ments and often profess complete igno-rance of any form of the others!

To form the basic stock etching solu-tion, water is added in the ratio 2 parts water to 1 part ferric chloride solution resulting in a solution strength of 42º Baume.

Preparing the solution

At this stage the strongly acidic ferric chloride requires further treatment to remove free acid and to 'condition the solution'.

Either small quantities of copper may be added and allowed to dissolve or (a more effective way) take 10 cc of the stock solution and add 10 cc of 9% household ammonia solution.

This results in a sludge of ferric hydrox-ide which is allowed to settle before pouring off the liquid and adding the precipitate to 1 litre of the stock solu-tion.

Once an etching cycle using ferric chloride has been initiated the third method is probably easier.

Here spent ferric chloride liquor (containing ferric hydroxide) is added to the new stock 42º Baume solution, in the proportion 1 part spent liquor to 10 parts 42º Baume solution.

Colour in use

The optimum etching conditions usu-ally occur after some etching has been done (this reflecting an 'incubation' period for the chemical reaction to 'settle down') but as etching proceeds the solution becomes less effective.

The progress of this exhaustion can be oh served by the colour changes - from an initial red brown (ferric hydroxide) through a turbid (muddy) brown (ferric and ferrous hydroxide) when the solution is working at its most effi-cient, and finally to a dark green solu-tion and black precipitate (cupric salts in solution and precipitated with the hydroxides).

At this stage the solution is exhausted and requires disposal. This can be effected by the slow addition of either calcium carbonate (whiting) or sodium carbonate (washing soda crystals) - until effervescence ceases. At this point the solution is neutralised and may be disposed of safely.

The myth upside down

The normal recommendation is to bite copper plates in ferric chloride in-verted or on edge to avoid precipitated ferric hydroxide clogging the etched line, thus halting etching.

However, there is little need for this if the plate is bitten face up' and removed from the solution every 20 min then washed in cold running water to remove the pre-cipitate before continuing to bite.

This procedure does not present the hazard of other etchants and has the advantage of checking progress. Extremely deep bites or plates for relief etching are still bitten upside down.

On completion of any biting, or if the plate is to stand between bites for any length of time, it should always be cleaned thoroughly with running water, since residual ferric chloride in bitten lines will continue to react.

Ease of use

To summarise, ferric chloride is a chemical and should be handled with respect.

However, it does not present the level of hazard associated with nitric acid and Dutch mordant; indeed the only precautions necessary are to use goggles and gloves, keep the solution in a plastic bath, and wash off any liquid on the skin with water. Extraction and fume cupboards are not necessary.

A 42º Baume solution at its most ef-fective is very good for a deep line bite.

When diluted to approximately 32º Baume by the addition of an equal part of water, it becomes very effective for soft ground and delicate work without a noticeable loss of biting time, and re-duces foul biting.

Due to the low depth of bite necessary in aquatint, the strength of solution does not greatly affect time taken to create a black, therefore strength of solution tends to be a personal taste.

The minus side is the length of time taken to bite a plate: half an hour in stock solution for a black aquatint, and an hour for an aver-age etched line.

Very deeply bitten lines may take several hours.

Notes

1 To speed the process, some sources recommend agitation of the solution by bubbling air through an upright tank.

Whilst this undoubtedly works there is a risk of hydrogen production by reac-tion with hydrochloric acid.

Therefore either extraction or a constant and ade-quate flow of air is required to prevent hydrogen build up.

2 It is preferable to use industrial grade 45º Baume ferric for both cost and speed (obtainable in the UK from Ellis and Everard) these less refined solutions often bite faster and it is the safest way t&) buy the salt.

Merck chemi-cals sell small quantities for laboratory use but this is the Analar pure grade at a 60% weight per volume ratio.

This needs greater dilution to 42º Baume and tends to be a slower acting form of the salt.

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كلوريد الحديديك (مواصفاته/تحضيره/استخداماته) Ferric10

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ferric chloride types/applications

1. LIQUID FERRIC CHLORIDE:-

Liquid Ferric Chloride solution of Iron III Chloride (FeCl3) in water.

It is manufactured by virgin raw material in an oxidation process using chlorine and Ferrous Chloride solution.

2. ANHYDROUS FERRIC CHLORIDE:-

Our ferric chloride is prepared by direct chlorination of iron with chlorine and product is collected after condensation of sublimed products.

Thus the process conditions are adjusted in such a way that material of highest purity is obtained.

3. LIQUID FERROUS CHLORIDE:

Liquid Ferrous Chloride is a concentrated solution of Iron II Chloride (FeCl2) from high purity raw materials.

It is the result of the dissolution of Iron Oxide and Iron in Hydrochloric acid.

APPLICATION OF FERRIC CHLORIDE:-

Ferric Chloride Anhydrous is hydrolyzed in dilute solution forming a precipitate of Ferric Oxide.

This precipitate absorbs suspended particles (clay, organic matter, etc) flocculates and carries the absorbed particles to the bottom. It also removes sulphides and silica.

It increase the rate of settling of sludge in sewage by the process of hydrolysis forming Ferric Hydroxide which acts as a coagulant.

Generally industrial effluents are either acidic or alkaline and the treatment of such effluents is usually a costly and cumbersome multi-stage operation requiring a number of chemicals.

Ferric Chloride Anhydrous because of its flocculating and deodorizing properties, can be used directly in a single stage operation replacing the traditional cumbersome process.

To release entrapped oil from crevices and rocks below the sea bed Ferric Chloride Anhydrous can be used by feeding it into the drilling well.

It decomposes and reacts with the rocks, releasing the entrapped oils which are removed by the normal processes.

OTHERS USES:-

FERRIC CHLORIDE ANHYDROUS CAN BE USED:-

As an etching agent for photo engraving and printed circuitry

To produce decorative surface effects on ceramics.

In the manufacture of glycerin.

As a catalyst, mordant, oxidizing, chlorination and condensing agent.

As a disinfectant, pigment and cattle feed-additive.

FERIC CHLORIDE FOR COPPER ETCHING

Copper Etchant

Ready to use solution designed for etching printed circuit boards and other metals. Recommended for use with M.G. Chemicals Professional Etching Process Kit (416-E) and M.G. Economy Etching Process Kit (416-ES). Note: Do not dilute this product with water.

Directions

Immerse copper board in solution and agitate until etching action is completed.

Ferric Chloride can etch up to a maximum of 100g of copper per liter of solution (.33 square meters or 3.5 square feet of 1 oz copper clad board).

Etching process can be sped up by heating the solution to a temperature no higher than 55°C (135°F).

If you require further directions for etching or making a printed circuit board, consult the positive photofabrication process guide available free from your dealer.

Specifications

General Specifications:

Phase:
Ferric chloride (Fecl3) liquid solution

Specific Gravity:
1.4

Molecular Weight:
162.21

Appearance: dark brown
Boiling Point: 106 °C
pH (5% by volume): 1.0-2.0
Freezing Point: 0 °C
Technical Specifications:

% FeCL3:
38.8

%FeCL2: 0.20
%HCL: 0.18
Insolubles:
<0.5

Metal Analysis:

Metal Result (mg/Kg)
Arsenic N/D
Bariuum N/D
Beryllium 4.8
Cadmium N/D
Chromium 64
Copper 77
Antimony N/D
Mercury N/D
Magnesium 15
Manganese 410
Silver N/D
Nickel 24
Titanium 18
Lead 59
Selenium N/D
Zinc 8.3
Vanadium 5.8
Sulfur 18
Thallium 2.7
Operating Conditions
Maximum Copper holding capacity
100 grams / liter or
(.33 square meters or 3.5 square feet of 1 oz copper clad board)

Etch rate
175-200 µin /minute @ 50-55 °C
(µin= microinch)

Temperature 50-55 °C

Available Sizes

Catalog Number Sizes Available Description
415-500ML 500 mL (17 oz) Liquid
415-1L 1 L (33 oz) Liquid
415-4L 4 L (1 gal) Liquid
415-20L 20 L (5.3 gal) Liquid

كلوريد الحديديك

الملامح العامة

كلوريد الحديد الثلاثي مركب كيميائي له الصيغة FeCl3 ، ويكون على شكل بلورات صفراء (سداسي هيدرات) .

الخواص

حالة أكسدة الحديد في هذا المركب +3 يحتفظ بالرطوبة ويوجد غالباً على شكل سداسي هيدرات، وله رائحة كلوريد الهيدروجين على الغالب.

يذوب مركب كلوريد الحديد الثلاثي بشكل جيد في الماء مشكلاً محلولاً ذي خاصية حمضية حيث أن الأس الهيدروجيني لمحلول 0.1 مولي مقداره 2.0، كما يذوب أيضاً في الإيثانول والأسيتون وثنائي إيثيل الإيثر.

الشكل اللامائي له بلورات لونها أخضر لها بنية كلوريد الكروم الثلاثي وتتسامى عند حوالي 120°س

في الحالة الغازية يمكن الحصول على متماثر ثنائي ديمير Fe2Cl6.

المحاليل المائية من كلوريد الحديد الثلاثي لها لون بني نتيجة الحلمهة (إضافة الماء). بإضافة حمض هيدروكلوريك يصبح المحلول رائقاً وله لون أصفر بسبب انزياح التوازن في عملية الحلمهة نتيجة ازدياد تركيز أيونات (شوارد) الكلوريد في المحلول، وبسبب تشكل معقدات من رباعي كلوريد الحديد
- [FeCl4]

التحضير

يحضر كلوريد الحديد الثلاثي من تفاعل غاز الكلور مع كلوريد الحديد الثنائي في وسط مائي حسب المعادلة:

2[Fe(Cl2)(H2O)4] .2H2O + Cl2 → 2[Fe[H2O]6]Cl3
يحضر الشكل اللا مائي من كلوريد الحديد الثلاثي من تمرير غاز الكلور على الحديد عند درجات حرارة مرتفعة.البنية
يكون الترتيب الحقيقي لمرتبطات الماء حول ذرة الحديد المركزية على الشكل التالي:

[Fe(Cl2)(H2O)4]Cl.2H2O

حيث توجد ذرتا الكلور بموقع مفروق (ترانس) بالنسبة لبعضهما البعض في بنية كلوريد الحديد الثلاثي ثمانية الوجوه.

الاستخدامات
يستخدم مركب كلوريد الحديد الثلاثي في أحواض الصباغة وفي المطابع.

يستخدم بشكل واسع كمادة كاشطة etching وذلك للخواص المؤكسدة القوية خاصة في مجال الإلكترونيات.

Cu + 2FeCl3 → CuCl2 + 2FeCl2

الشكل اللامائي من كلوريد الحديد الثلاثي يعد من أحماض لويس القوية لذا يعد من الحفازات المهمة للتفاعلات الكيميائية، من أشهرها تفاعل ألكلة فريدل كرافتس.

الاستخدامات الصناعية

.أ. يسخدم في تنقية مياه الشرب كما يستخدم في معالجة مياه الصرف الصحي للتخلص من أملاح الحديد.

ب. يستخدم لازالة الكلور من المعادن وتنقيتها

ج. كما يستخدم كعامل محفز في تفاعلات الكلور مع الايثلين لانتاج كلوريد الايثلين المستخدم في انتاج كلوريد الفينيل الذي يمثل المونمر بالنسبة لـPVC
الاستخدامات في المختبر

يستخدم كلوريد الحديديك كحامض لويس لتحفيز تفاعلات اكلة فريدل كرافتس