Common chemical products

The multiple possibilities of chemical products usable in restoration are described here. Safety and handling equipment are mentioned.
The presentation is divided into 9 chapters and covers the following points:

1. Safety — equipment.
2. Acids.
3. Bases or hydroxides or alkalis.
4. Water.
5. Solvents.
6. Glues.
7. Copper strippers — aluminum strippers — iron strippers.
8. Printed circuits = lacquers and products attacking copper.
9. Miscellaneous.

The use of acids, alkalis, and other products requires safety measures which are: wearing goggles, gloves, aprons etc., made of plastic for example, no open flames, effective ventilation.

All chlorinated products are anesthetic to varying degrees and always toxic. The other solvents used in amateur radio DIY are no better. Inhalation should be avoided even if their "odor" is pleasant to breathe. In addition, some are flammable.

Breathing carbon tetrachloride for 15 seconds for potentiometer degreasing and then a quarter of an hour later cleaning a chassis with perchloroethylene; ten minutes later preparing a solution of hydrochloric acid from concentrated HCl; transferring ammonia; all this is harmful and requires ventilation; every amateur radio operator owns a small fan that they will direct from above towards their work area and thus dispel harmful fumes.

Chemical products must be kept out of reach of children. All bottles containing chemical products must be labeled (protected by a layer of paraffin) or have an indication on a "tag", including the name or formula of the product, its concentration, and its date of manufacture.

Store solutions in brown bottles and away from sunlight because secondary reactions are possible with product transformation and gas release leading to explosion. Example: TRICHLOROETHYLENE + traces of water + sun ==> acidic product + toxic gas. Also be careful with Ammonium Persulfate and hydrogen peroxide at 30 volumes (H202 at 30 v.).

Hydrochloric acid (spirit of salt) bottles must be closed immediately after use and residues eliminated and rinsed; without this precaution, the next day all your tools will be rusty if this happens in the "shack", the bare copper of components or devices suffers the same damage.

During the use of chemical products of any kind, a bucket filled with water near the workplace is a good precaution to take. A damp cloth is useful. These recommendations are not a luxury or a whim because the slightest inattention can cost dearly. A droplet of acid or lye in the eye can cause blindness in a few moments.

• A 100 cc (cubic centimeter or ml milliliter) graduated glass cylinder allows all the measurements indicated in this summary.
• A glass funnel preferably. (Why glass equipment? Because it can be used with all solvents without damage).
• 3 or 4 containers (+ lids) from "ice cream" YSBOERKE or similar Easy maintenance and unalterable material Dimensions: 200mm / 140 / 100 .
• 1 larger container that can hold a "ice cream" container and comes from a "liquid soap container" made of plastic, cut in the right place lengthwise, serves as a water bath and also contains lukewarm rinsing water.
• Some clear plastic bottles (like Spa Reine) for storing solutions.
• Two or three "Spa Reine" bottles cut at 8 cm from the neck for soaking baths.

H₂SO₄, Zwavelzuur für Schwefelsäure, concentrated acid, vitriol, 66° BAUME, battery acid, 22°B or supplier indication. Its use in radio DIY is not justified except for battery users.
Prepared acid is sold in drugstores or "auto parts stores".
Sulfuric acid is dangerous and absolutely requires protection with goggles, gloves, aprons, etc. Its reaction with water releases intense heat which requires an appropriate container for dilution.
Never pour water into concentrated acid, but slowly pour the acid into the water, otherwise there is a risk of acid splashing.
Burns from sulfuric acid cause the destruction of flesh which does not regenerate (vitriolage).
Store acid in a glass or APPROPRIATE plastic bottle - never a cork stopper.
Always affix a duly completed label protected by a layer of paraffin.
In case of skin contact, wash thoroughly with running water and consult a doctor.
The concentration is determined by chemical titration or simply using a hydrometer - respect the temperature for the measurement. (For the dilution of powdered ferric chloride or the dilution of other acids, the same precautions should be taken).

DO NOT USE IN CONCENTRATED SOLUTION BECAUSE OF TOXIC FUMES.
For cleaning copper from PCBs: 2% acid solution at 40° B.
Maximum contact: 1 minute.

Used for cleaning heavily rusted iron or for dissolving limescale.
It attacks skin, clothing, and pavements - When using it safety measures are absolutely essential - In case of burns, wash with plenty of water.
An open bottle of HCl for one hour is enough to "rust" all the tools in your workshop and to attack the copper of your devices. (See 1.1. 7.)

Dangerous like the preceding acids, but effective for "blocking" rust.
Phosphoric acid transforms rust into insoluble iron phosphate.

Pale yellow, odorless, soluble in water, shiny crystals.
Used to daub small, unopened burns made with the soldering iron and allows continuing work without pain because it acts as a tanning substance. Apply with a small brush or with cotton wool.
Stains skin and textiles.
It can be used to brown or blacken iron.

(Salt of sorrel) - White crystals soluble in water - bought in drugstores - POISON!!! .
Prepare a saturated solution with rainwater or distilled water.
This organic acid is very useful for removing rust stains in general and in particular those caused by ferric chloride on fabrics.

Use

Place the fabric on a glass plate or a sheet of plastic, touch the stain with the oxalic acid solution using a small stick whose end has been coated with cotton wool, DO NOT RUB. Oxalic acid transforms the iron (brown) of the stain into colorless and soluble iron oxalate.
Rinse carefully with water. Repeat the operation if traces remain.
RINSE and REWASH the fabric otherwise holes may form at the stain locations. Never let oxalic acid dry in textiles. The hole is not caused by acidity, as it would be with the mineral acids mentioned previously, but by the formation of sharp-edged crystals that shear the fibers of the fabric with the slightest movement of the textile.

These are products "opposite" to acids and therefore neutralize them. It is absolutely necessary to take the same precautions as for the use of acids.
Never use glass stoppers on soda bottles.

Soda lye. It is the strongest and most dangerous alkali for eyes, skin, nails; it dissolves flesh.
In contact with water, solid soda produces an exothermic reaction (heat-producing), its use therefore requires the use of an appropriate container and in particular no galvanized metal bucket or aluminum container.
Proceed in small quantities at a time, let cool, and so on. Do not use hot water as there is a risk of splashing.
In case of soda burns, rinse with cold water and finally
with water containing a little vinegar so that the "greasy" sensation caused by a soda burn disappears.
For the eyes, consult an ophthalmologist IMMEDIATELY.

(Caligene.) - Same properties and same dangers as caustic soda
Used to strip paints except latex.
A 20% by weight KOH solution (density 1.25) is used for Nickel-Iron batteries.

Used to clean files clogged with aluminum filings (by soaking).
Used to dissolve the resin of printed circuits (PCBs) after exposure to ultraviolet (UV) light. The usual solution for this purpose is 7 grams of soda per liter.
See chapter VII: etching aluminum for "satin finish".
Preparation of a soda solution at a concentration of X grams per liter from caustic soda pellets (DIY store)
Weigh, for example, 100 grams of pellets (immediately close the bottle). In a plastic container (Spa Reine), pour 500 cc of soft water (or rainwater or distilled water) - add little by little the 100 grams of granules, mix, then make up to 1 liter with distilled water, i.e., 1000 cc in total.
There is therefore 1 gram of pure soda per 10 cc of solution.
Example: To make a solution of 7 grams of soda per liter: measure 70 cc (using the 100 cc graduated cylinder) of the 100-gram stock solution prepared previously and make up to one liter, i.e., add 930 cc of distilled water. Stick a label on the bottle indicating the formula, concentration, and date of manufacture. The bottle must remain closed, otherwise the soda loses its strength due to its reaction with the carbonic acid in the air (CO2).

Solvay Soda - soluble in hot water.
or Soda Crystals: NA2CO3.10H20 - same product but crystallized and soluble in cold water.
WARNING these products are not BICARBONATE of soda.
Carbonate is a medium-strength alkali used to neutralize acids spilled on the ground or poured down the drain.
It is also used to degrease metals; Solvay soda plus hot water saponifies vegetable and animal fats, like caustic soda for that matter, but in a less dangerous way.
Rinse with water after use.

- AMMONIA solution
- AMMONIAC gas - NH3
Ammonia is an aqueous solution of ammonia gas.
Usual safety: do not breathe the fumes, turn on the small fan.
Ammonia dissolves copper, and the fumes superficially attack bare conductors even several meters away.
Cleaning by soaking files clogged with copper or brass. Rinse and dry after cleaning.
Recover ammonia solutions in a plastic bottle for secondary uses (see chapter IV).
Any contact of ammonia with the skin must be washed with plenty of water.

WATER.

H²0 - water - Wasser - pure water is neutral - Water collected in the city is acidic (pollution).
The water used to make solutions of bases, acids, or other products chemicals can be:
a) distilled or demineralized water, b) rainwater.
Rainwater is sufficient for the needs of the amateur radio operator. Take a plastic container well rinsed and cut lengthwise, which gives two large recovery surfaces that, placed on a terrace or in the garden, quickly provide a significant volume of water - given that it rarely rains in our country. Another way is to place a soft plastic pipe (10 mm diameter) in a downspout, leading to a clean bottle below - you can filter this water through cotton wool placed in a funnel.
Store water away from light (because of the formation of green algae).
Water from schistose regions is generally soft and can be used as is.
Do not use hard water as it leads to secondary reactions and unpleasant deposits.
Water collected in the city is not always pure (dissolution of combustion gases) ; discard the first roof cleaning water; however, it can be used to dilute acids or bases.

ex: diesel, kerosene, turpentine, white spirit, gasoline (+ lead salts).
Fatty solvents leave a greasy film after drying.
They can be used for large cleanings outdoors. Do not use them in radio.

Give various reactions. - Are anesthetic and harmful.

Perchloroethylene C2Cl4 Dry cleaning solvent Perchlorathylen.
Per is non-flammable, heavier than air, than water, as are its vapors.
It is a chlorinated solvent that leaves an acidic reaction.

Trichloroethylene - C2HCI~ - Trichlorathylen.
non-flammable. WARNING
PER and TRI, like most chlorinated solvents, form HCl in the lungs. If you smoke while using these solvents, the vapors passing through the cigarette, cigar, or pipe transform into phosgene = Yperite from World War I.
These products degrease the skin and can cause eczema.
Use only outdoors - do not breathe - do not use in radio circuits. Use the small fan to blow the vapors downwards.
Ventilation should be placed at the lower part of the workshop.

CH-CO-CH - acetone - Azeton - FLAMMABLE.
Acetone dissolves certain textiles (acetate) and attacks almost all plastics, paints, and varnishes, and many radio components. Used to remove varnish from printed circuits after treatment with ferric chloride. Very volatile, do not breathe it.

CH~-COOCsH11 - Amylacetate - Amylazetat - Pearoil - Bananaoil - Birnether.
Properties almost identical to acetone, less active on acetate and less solvent; its reactions are slower, and it is less volatile.
Used to deodorize kerosene. Removes hardened or fresh "latex" paint stains on all surfaces, as well as old oil-based paints or varnishes.
Rinses with water or Per (during dry cleaning), for example.
See special properties for the manufacture of lacquers for PCBs in chapter VIII.

CH30H - Methanol - Methylalkohol - wood alcohol - POISON.
Used as a cleaner and solvent; removes excess solder paste after soldering on PCBs; Antifreeze.

C2Hs-OH denatured - Ethanol - rubbing alcohol - POISON. - Athylalkohol Denaturierter (Spiritus). - idem methanol.

CCl4 - Tetrachlorkohlenstoff - Non-flammable - formerly used in fire extinguishers.
Former "SASSI" stain remover, the best solvent for amateur radio operators because it leaves no trace, neither acidic nor basic; removes the grease film plus the dirt that adheres to it.
Rapid evaporation, does not attack radio components.
Used by "spray" or better, by atomizer or brush.
Ideal for cleaning crackling potentiometers or for restoring old radios.
Sold in drugstores. "Sprays" of commercial products for equivalent uses are sold ONE HUNDRED TIMES the price of pure carbon tetrachloride.
Very TOXIC vapors - anesthetic) small fan.

CHCl~ non-flammable - anesthetic - small fan.
Can be obtained from your pharmacist in small quantities.
Not used in radio for its solvent quality because it dissolves certain plastic elements (used in the manufacture of many components).
See chapter VI: glues.

This fatty solvent is used to loosen rusted equipment, bearings, bushings, thrust bearings, etc.
Action by soaking the part; if the rust attack is deep, the result may be slow to appear.
Recover and filter the petroleum after use.

We will not discuss commercial glues here, which are as numerous and varied both in terms of price and in the field of applications but glues useful for the OM (Old Man, ham radio operator) and achievable at little cost.
The most economical glue is made with waste or better with Plexiglas sawdust dissolved in chloroform. Two methods are possible for gluing:

6.1. GLUING TWO PLEXI PIECES.

For example, to fix the wires of an air-wound coil, for supports, angle brackets, ..., insulators; to make airtight dipole centers, etc.
The two parts are sawn or adjusted with a circular saw or a hacksaw.
Do not polish the surfaces to be glued. A few scratches from a medium-fine file are favorable to the diffusion of chloroform on the parts to be glued.
Place the two parts to be glued in their final position and fix them if necessary with a clothes peg, a weight, or a clamp.
Take a recovered syringe and draw a little chloroform into the cylinder.
Pour a thin stream of chloroform into the joints formed by the two parts to be glued.
Let dry at a good temperature or near a radiator.
Wait half an hour before checking the strength of the bond.
Add a stream of solvent if necessary. Let dry thoroughly.
The glue is invisible, unlike some commercial glues that contain air bubbles, and leaves no trace on the parts glued.

THICK GLUE.

Applied with a brush or spatula.
For gluing materials of various kinds (preliminary tests necessary).
This glue is made of waste, trimmings, Plexiglas sawdust dissolved in chloroform. The consistency of the glue depends on the amount of solvent used. Clean the cap or thread of the
bottle before closing it; if it gets stuck, a stream of chloroform will fix things. The parts to be glued must be degreased beforehand with chloroform.

Plastic solubility TEST.

Pour a drop of chloroform or another solvent onto the plastic to be tested, let it act for a few seconds, and test with your finger whether there is dissolution or not.

MEK: methylethylketone.

Flammable. Solvent for inks and certain plastics.
MEK is used to glue ABS (Acrylonitrile Butadiene Styrene), a plastic that is increasingly common and works well with saws, files, lathes, or knives.
MEK is used like chloroform.
Gluing is done quickly, but the major drawback is that it leaves marks with the slightest contact.
ABS can be glued to Plexi: process to be examined!
EXPANDED POLYSTYRENE = STYROFOAM.
Insulation material, packaging, etc., soluble in MEK. This solution hydrophobic is used to waterproof mast feet, supports, etc.
A viscous solution is suitable. Let dry between one or several coats. It is best to do preliminary tests.

• for iron
• for copper
• for aluminum
• for printed circuits
• essential safety and ventilation - small fan.

IRON STRIPPERS.

First degrease the iron.

HYDROCHLORIC ACID.

HCl, rust reforms after treatment.

PHOSPHORIC ACID.

H3PO4, rust is "blocked" after treatment by the formation of insoluble iron phosphate.
Instructions for use:

• Depending on the size of the surface to be treated, proceed with a brush (with synthetic bristles) or by soaking.
• The concentration ranges from pure to 50/50.
• Several brushings are sometimes necessary.
• As soon as the iron is silvery, rinse thoroughly with water, wipe, then dry.

For lasting protection (outdoors), paint the iron with oil-based paint, metal varnish, or Black Varnish based on bitumen (DIY store). No Latex!

7.2. STRIPPERS FOR COPPER AND ITS DERIVATIVES.

First degrease. With pumice powder (or VIM or AJAX) and a wet Spontex sponge, clean the copper surface until a uniform pink tint is obtained. Rinse, then treat with a clean Spontex sponge plus pumice and 2% HNO3 for about one minute. Rinse with water directly after stripping. Dry with a clean, lint-free cloth and immediately photosensitize away from light with POSITIV 20 (Kontakt Chemie) before the copper reoxidizes.

ALUMINUM STRIPPER.

First degrease.
Caustic soda vigorously attacks aluminum.
Various concentrations are used (normally: 5% solution) to "SATIN" the shiny aluminum, i.e., make the surface matte, either to leave it as is or to allow the "adhesion" of a subsequent paint.
A test is necessary to determine the reaction time. Aluminum attacked by soda produces hydrogen fumes, so it is imperative to work away from any flame or incandescent object (cigarette) and in a well-ventilated area. If you don't want to send the shack into orbit - small fan outside.
Note for perfectionists: if you want to obtain a "commercial" velvety finish, you can add 0.5% sodium gluconate from PFIZER to the soda solution.
The most spectacular application of AI etching is the following. To fit two ALU antenna tubes together, e.g.: (A) 25 X 21 mm to be inserted into (B) 28 X 25 mm - without sandpaper, without a lathe, without effort - remove the cutting burrs from A and B. Place A in a "Spa Reine" container, pour a caustic soda solution up to the distance by which the diameter needs to be reduced. Let the solution act and ventilate to evacuate the hydrogen formed. After 30 minutes, remove the tube, rinse it with water (dry with a clean cloth), measure to the nearest 1/100th and judge the time it will take to reduce the diameter by 2 or 3/100ths. After 2 measurements, try to insert A into B. Never force A into B, as it would be impossible to extract it. A must enter B with gentle friction. At this point, fix the tubes with slots + hose clamp or with bolt + nut all the way through.
NOTE: Tube A can be plugged with a plastic stopper so as not to attack the inside.
Safety: put the soda back in place + label. Safety first.
In any case, and this applies to all etched metals including PCBs, preliminary degreasing is essential and when the work is finished, the treated surface can no longer be touched with fingers (put on rinsed plastic gloves with water before touching the metal). Traces of fingerprints sometimes only appear after several months on the surface of the metal; it is then too late to rectify.

LACQUERS.

For "fun" when you need to cover large areas of a circuit
board, you can make a lacquer a few days in advance that will protect the copper from ferric chloride etching.
8.1.1. Certain colored toothbrush handles preferably - yellow BIC razors - black or red BIC are soluble either in acetone or in amyl acetate or other dry solvent (to try in a small airtight bottle).
Play chemist to give an ideal viscosity for your tracings either with a "reservoir pen" or with a brush or ordinary pen. Be careful when closing the bottle (blocking) if there are traces of varnish on the edges. Clean the equipment with the solvent used to dissolve the handles.
Black or red "handles" give a more visible lacquer on PCBs.
8.1.2. Shellac flakes.
Dissolve in methanol or ethanol.
Disadvantage: little coloration unless a dye soluble in alcohol is added!
8.1.3. Universal lacquer.
"Miracle" product for the DIYer because it has several properties:
Covering product for PCBs (very little colored unless a soluble dye is added in alcohol).
. Dissolve 50 gr of powdered rosin in 100 cc of isopropyl alcohol CH3CH-CH8 preferably (at a pinch in ethanol or methanol). Do not go below 40 gr of rosin per 100 cc of alcohol to make the solution because at this concentration the varnish is porous. More than 50gr/100cc of alcohol is fine if the viscosity suits you; test first. This lacquer resists FeCl3
. Ease of soldering after the lacquer has dried (tinning of large surfaces); even with tin without a resin core.
. For quick and efficient soldering of integrated circuit sockets or transistors, dip the ends of the pins or legs in a lacquer solution of 1 to 2 mm thickness, let dry, place the
material in the hole of the printed circuit board, SOLDER.
. Protective lacquer against oxidation (almost colorless as is). . Cleaning with alcohol.

REMARKS

Dissolutions are not as fast as high frequencies, but are faster near a
radiator than in the fridge. Stir the solution from time to time.
The coloring of lacquers is done with dyes soluble in alcohol, or directly by the coloring of the base plastic used; red or black plastics are the most effective for visible tracing of PCBs.

ETCHING CHEMICALS FOR PRINTED CIRCUITS.

Etching chemicals for Printed-Circuits (PC boards).
Beizchemikalien fUr Printplatinen.
The following list of etchants is provided for documentation purposes only. It can be used for experimentation by an OM wishing to break with routine.
These different formulas, along with many others, are used in specialized industry, and new techniques are constantly appearing.
Adequate equipment is necessary.
Etching is done by various processes:
1" By spray: circulation of the bath projected onto the PCB by spraying in a sealed container.
2" By air bubbling: air insufflation by a small compressor or aquarium pump; the PCB is placed vertically.
3" By bath circulation: sucked at the bottom and diffused above the PCB. 4" By immersion: with mechanical or manual agitation. The PCB immersed
in the bath and taken out into the air by means of a nylon thread during the etching time. This system is process n°2 without equipment.
For the DIYer, not having many PCBs to make, the method by air bubbling (n°2) or (n°4) is the simplest, the most rational and the fastest (5 to 10 minutes).
The compressor or pump must be placed higher than the level of the bath (avoid accidental backflow).
The etching room must be well ventilated and the safety instructions respected (small fan running !).
The equipment for 1, 2, and 3 must be sealed to avoid acid splashes; desired solution temperature: from 25 to 35 degrees Celsius using a water bath.
Ventilation with an expansion and recovery chamber is necessary; a plastic tube (6 to 10 mm OD) fixed in the lid (sealing necessary for example: Silicone sealant) is directed into a stable container under the workbench, for example, a magnum of champagne, empty naturally!!!

8.3. Some formulas used for etching.

8.3.1. Before listing some formulas, let's examine ferric chloride and how it attacks copper.

Ferric perchloride - ferric chloride - anhydrous FeCl3 - FeCl3.6 H20. IJZER (III) chloride - Ferric chloride - EISEN (III) - chloride.
Industrial production: adequate treatment of effluents from cleaning with conc. HCl of irons coming out of rolling mills (OM, Metallurgists, take advantage of it!)
FeCl3 is sold in drugstores or specialized stores either in solution of various concentrations - or in plastic bags of 250 to 1000 gr containing a yellow agglomerate allowing you to prepare yourself solutions at known concentrations.
The ideal concentration for the highest etching speed is 30 - 33' B i.e., +/- 30% FeCl3 or 48% FeCl3.6 H20.
From 40 to 45' B, the etching is slow and reserved for fine work. - The temperature usually recommended is from 25 to 30' C. - The action of FeCl3 is always regular.
The etching of copper is given by the following reaction:
2 FeCl3 + Cu --) 2 FeCl2 + CuCl2.
Why is agitation of the bath during etching necessary? The mixture of CuCl2 (cupric chloride) and FeCl2 (ferrous chloride) which forms during etching has a creamy consistency. It therefore remains stuck to the copper, which isolates it from the subsequent action of the perchloride, thus decreasing or stopping the etching of the copper.
. Immobility of the bath prolongs contact up to one hour and favors the infiltration of acid under the protective layer through the grooves dug by the abrasive material used for the initial mechanical cleaning.
, By stirring the bath or better by bubbling air into it, you get the double advantage of stirring the bath, oxidizing the solution, and thus quickly eliminating the "oily" layer, sometimes reducing the removal of copper to only a few minutes.
, Of course, the fresh perchloride bath wears out as you go along with the number of boards processed. This results in a reduced etching speed, which manifests itself by a prolongation of the duration of the etching.
The bath also changes from red to greenish.
. In principle, the bath should be replaced as soon as its etching time is doubled.
. There is a way to control the degree of wear of the bath by its copper content. 1 cc of used solution is treated with ammonia to precipitate the iron in the form of ferric hydroxide (rust color), then after filtration and washing, the blue solution is compared with several standard solutions of copper sulfate (CUSO4.5 H20), but that is another story!
To hold the boards vertically during etching, a support can be made of Plexiglas triangles glued with chloroform (see chapter on glues).

8.3.2. Caution!

Some stores sell, for example, 250 gr. of FeCl3 for one liter of solution, others for 500 cc.
1 In fact, 250 gr of FeCl3 + rainwater to obtain 500 cc of final solution is the recommended concentration and gives +/- 30° B, i.e., 29% FeCl3 and 48% FeCl3.6 H20.
The solution at 250 gr to make up to one liter only gives 15° B, i.e., +/- 15.5% FeCl3, and is exhausted too quickly, and the etching takes longer.
A solution sold as a kit in a radio store is at 31% FeCl3 and gives good results.
A more concentrated solution containing 250 gr of FeCl3 for a final volume of 300 cc, i.e., 833 g of FeCl3.6 H20 per liter = 40° B, does not give a deposit after 24 hours at 15°C.
The industrial solution with a strength of 45° B is red-brown, sold in carboys, and is generally used as a flocculant in water purification. It can be used for the amateur's needs by diluting it.
Another formula for copper etching is composed of 44% FeCl3 + conc. HCl 4 gr/l + CuCl2 20 gr/l.
There is a lot of choice, but also many prohibitive prices!!

8.3.3. 600 gr/l FeCl3 solution:

The etching speed of this solution is faster than that of the formula

8.3.4 Disadvantage

The solution is not regenerated by oxidation, i.e., by air injection.

8.3.4. 600 gr FeCl3 + 300 cc conc. HCl / 1 solution

Etching speed slower than in 8.3.3, but regeneration by slow aeration for 24 hours

8.3.5. 30% HYDROCHLORIC ACID

It is foolish for the DIYer to make PCBs using this method, which is indicated for documentation purposes only.
Firstly, perhydrol is dangerous to handle. It strongly attacks the skin and eyes, hence the usual precautions to be respected. The solution attacks everything; moreover, toxic chlorine gas is formed - method not recommended.

8.3.6. AMMONIUM PERSULFATE

White powder - colorless solution.
Very energetic oxidant due to its heptavalent sulfur (S7++).
Copper oxidizing agent - keep cool and away from sunlight (explosion).
Recommended solution: +/- 220 gr persulfate/l + 10 mgr mercuric chloride (HgCl2 - poison) or 1 cc silver nitrate (AgNO3 NIlO), which acts as a catalyst, i.e., reaction accelerator.
This solution is clear but how dangerous compared to ferric chloride.
The FeCl3 stain is immediately visible, while that of persulfate is almost invisible and destroys undisturbed until the hole appears in the wood, paper, or clothing.
The etching speed varies depending on several physical and chemical factors, hence never identical results.
Moreover, there is no noticeable color difference to indicate its degree of exhaustion.
In principle, a fresh solution is needed each time!
Note: Kontakt Chemie recommends 538 gr persulfate per liter at 40°C, with
continuous agitation - etching time: 10 minutes.
According to Marcel Boll, a diluted solution of NH4 persulfate decomposes around 20°C without releasing oxygen because the latter is used to transform part of the nitrogen into nitrate anion according to the reaction (NH4)2 S20e --) 16 SO4- + 2 NO3-- + 20H+. Therefore, a very aggressive solution composed of sulfuric acid + nitric acid.
At higher temperatures, oxygen is released, and sulfuric acid is formed.
Therefore, two different attacks depending on the operating temperature!!