How to make quality CDS
The products and materials needed to manufacture your own CDS at 3000 ppm.
Products and Materials
Products:
Sodium Chlorite [ NaClO2 ].
Hydrochloric acid [ HCl ].
Water [ H2O ].
Sodium Chlorite [ NaClO2 ], sold as a powder at a concentration of approximately 80%, or as a solution at a concentration of approximately 25%.
As Sodium Chlorite will not be consumed but only used for making CDS, so there is no need to use medical grade.
Note:
Sodium Chlorite has nothing to do with bleach which is a solution of Sodium Hypochlorite [ NaClO ].
The Sodium Chlorite powder must be diluted with water to obtain a concentration of 25%, which is the one that will be used to manufacture the CDS.
Recommendation:
NaClO2 should preferably be stored in a cool place away from direct light.
NaClO2 is a powerful oxidant, avoid putting it near flammable products.
Also possibly on sale at pool equipment suppliers.
Hydrochloric Acid [ HCl ], sold in bottles at various concentrations ranging from 4% to 37%. Can be found in supermarkets (23%) or building materials stores (35% to 37%). If you find 4% or 5% you won't have to dilute it.
Recommendation:
Hydrochloric Acid is corrosive especially at high concentrations, so avoid contact with skin and especially eyes. Care should also be taken not to inhale the vapors, as this may irritate the lungs. Protective goggles in addition to disposable gloves and a mask (wet if possible) are recommended during handling, preferably in a ventilated place. In case of acid splash, immediately wash the affected area with running water for at least 3 minutes.
Water [ H2O ],
we will use either distilled water, or demineralized or deionized or reverse osmosis water, or as a last resort, very low mineralized water that can be found in supermarkets or pharmacies. Avoid tap water because it is often chlorinated.
If you have no other choice but to use tap water, it should be left to settle for a few hours in an open container, in order to let the chlorine escape.
Equipment:
A sealed glass jar (mason),
"Ikea - Korken" or "Le Parfait" are good, with a capacity of one litre, sold in supermarkets. This jar will be used to saturate the water with chlorine dioxide gas [ ClO2 ]. We will call it the "Saturator".
Note: The rubber seals supplied with the jars disintegrate on contact with ClO2 gas, so use silicone seals instead.
Silicone seals are often thinner than rubber seals, so you may need to use two.
Remember to have spare seals, preferably in silicone.
A small glass,
choose an elongated glass or preferably a stemmed glass, which must be high enough to exceed the water level by about 1 cm and still allow the jar to close, leaving a space for the gas to diffuse into the jar. We will call it the "Reactor".
The higher the glass, the more water we can put in, and therefore the less air there will be in the jar. A stemmed glass will "displace" less water and therefore allow more to be put in.
A scale,
either digital or mechanical but sufficiently precise, with a measuring range of 1 to 500g.
Possibly a 2nd Scale, of sufficient precision to measure small quantities to 0.01g ready.
Syringes, of different sizes:
1ml,
5ml,
10ml,
20ml,
50ml...
and even 250ml to make transfers.
250ml
Brown glass bottles (Amber) to avoid UV, You will need several and if possible of different capacities (Typically 250, 500 and 1000ml). Also make sure the caps are tight, otherwise the gas will evaporate.
Avoid cork and metal stoppers.
Droppers and sprays are useful too.
Test strips used to test CDS concentration in ppm. These strips only allow to measure up to a concentration of 500 ppm, it is therefore necessary to dilute the CDS in order to measure the maximum possible concentration of 3000 ppm.
We can therefore choose to dilute by 10 or by 6, then multiply the value found by 10 or 6 respectively to obtain the detected concentration.
Here from the LaMotte brand.
Protective equipment,
for certain manipulations, it is recommended to take precautions, such as disposable gloves, dust mask and goggles against possible projections.
Where to buy the equipment and the products?
As an indication you will find here a list of suppliers for the material and the products used in the manufacture of the CDS.
Note: This list is based on European sources, so for other countries it is suggested you seek help of the various CDS groups in Telegram.
L'AU - Sources de produit et materiel pour faire du CDS + GEL.pdfThe method
Preparation of base product solutions.
Note: you can also find ready-to-use solutions, for those who do not want to make these dilutions themselves (see below).
Note: you can also find ready-to-use solutions, for those who do not want to make these dilutions themselves (see below).
Prepare the 25% Sodium Chlorite solution. We'll call it the CS-25.
To prepare this solution, dilute Sodium Chlorite [ NaClO2 ] powder at 80%, in distilled or demineralized water. This dilution will be easier with water at a temperature of 37° to 48°C (warm but not hot). Do not exceed the 48°C otherwise the Sodium Chlorite will degrade.
Example: To make a 25% NaClO2 solution, we will have to dilute 45.5g of 80% NaClO2 in 100ml of water, and will obtain ± 120ml of solution for a weight of 145.6g.
Recommandation:
NaClO2 is a strong oxidant, so contact with flammable material should be avoided. Care should also be taken not to inhale the dust, as this could irritate the lungs. It is recommended to wear disposable gloves and a dust mask.
Prepare 4% or 5% Hydrochloric Acid. We will call it the Activator.
To prepare this solution, the Hydrochloric Acid will be diluted in distilled or demineralised water.
Example: To make 100ml of 5%* acid from 23% we will take 21.7ml of 23% HCl and 78.3ml of water.
If you have 35% acid, we will take 14.3ml of HCl and 85.8ml of water.
Warning!
Never pour water into acid, always pour acid into water, otherwise you risk acid splashes.
Recommendation:
Hydrochloric Acid is very corrosive especially at high concentrations, so avoid contact with skin and especially eyes. The preparation will preferably be carried out in a well ventilated place in order to avoid inhaling the vapors, which could irritate the lungs.
It is also recommended to put on protective goggles in addition to disposable gloves and a mask (if possible wet) during handling.
In case of acid splash, immediately wash the affected area with running water for at least 3 minutes.
* I chose to use 5% hydrochloric acid rather than 4%, to obtain a faster activation and as the residue will not be consumed but used to disinfect, it will not have an influence on the CDS quality.
Suppliers of commodity products and ready-to-use solutions (for Europe):
Saturations.
First saturation (Day 1)
Preparation: The jar with a good silicone seal (the rubber is degraded by ClO2), the small glass, two syringes (one for the CS-25, one for the Activator). A 500ml jar can saturate up to 300-350ml of water, a one liter jar can saturate up to 850ml of water. Since silicone seals are generally thinner than rubber seals, you may need to put two on. Another solution is to put a freezer bag between the neck of the jar and its lid.
As a general rule, we will use 1.3ml of each solution for every 100ml of water. We can add more, but it will not necessarily have an influence on the final concentration of the CDS.
Example: 10ml of each for 800ml of water.
Prepare one of the syringes with between 5 and 10ml of CS-25 solution and the other with the same quantity of Activator, depending on the amount of water to be saturated.
Recap the CS-25 and Activator bottles.
Put the shot glass in the jar.
Fill the jar with water so that the water level is a little lower than the top of the small glass. For a liter jar, you can put about 800 ml of water, but the volume doesn't really matter.
Inject the contents of the two syringes into the reactor (the small glass) preferably starting with the CS-25 then the Activator and immediately close the jar, preventing the liquid from the reactor from spilling into the water. You can also inject the two solutions simultaneously, in this case, control the injection speed, because the reaction can be quite violent and cause an effervescence in the reactor, this is normal. The color of the liquid in the reactor should turn dark brown after a few minutes.
The production of ClO2 gas in the jar is now activated and this gas will be slowly absorbed by the water. It is better to have a jar where the air space is small, because the less room there is for gas, the more the pressure will increase and the faster the gas will be absorbed into the water (Henry's Law) .
Put the jar in the dark in a cupboard for 8 to 24 hours. Depending on the ambient temperature, the saturation can take significantly longer (up to several days). It is considered that the absorption is complete when the liquid in the two containers have the same color (color of sunflower oil).
When absorption is complete, put the jar in the refrigerator for at least 2 hours. This will have the effect of improving the dissolution of the gas in the water and reducing its loss when opening the jar.
Second saturation (Day 2)
Prepare the two syringes again with the same quantities of CS-25 and Activator as during the first saturation.
Take the jar out of the refrigerator and open it in a well-ventilated place and avoid inhaling the gas from the container.
Take out the reactor (the small glass) and pour the liquid (the residue) into a stoppered container to use as a disinfectant.
Note: You can also "aspirate" this residue with a syringe to transfer it, which avoids risky handling of the small glass.The water in the jar will have a concentration of approximately 1500 ppm or 0.15%.
Put the reactor back in the jar and proceed as for point 5. of the first activation.
Put the jar back in the cupboard for another 8 to 24 hours, until the liquids are the same color again (this time the color will be more like olive oil). The water in the jar should have reached a concentration of 3000 ppm or 0.3%.
When the absorption is complete, put the jar back in the refrigerator for about 2 hours, to reduce the loss of gas when opening the jar.
Take out the reactor and pour the liquid (the residue) into the container to be used as a disinfectant. We will keep this container preferably cool and in the dark, just like the CDS.
Test the result (the concentration in ppm)
To test the concentration of this CDS which we will call "stock solution" we use reactive strips.
As these can only measure up to 500ppm, to test 3000ppm we need to dilute the solution and then multiply the value read by the same factor. To do this, we add 9ml of distilled water to 1ml of stock solution.
It is imperative to respect the instructions for use written on the box of the strips, otherwise the result will not be fillable. Namely: soak the strip for 2 seconds in CDS diluted 1/10, then raise the strip head up for 10 seconds, then read the result immediately by comparing the color of the strip with those printed on the tube of the strips.
The color should be between 250 and 500ppm, or about 300 ppm. This multiplied by ten gives the concentration of our solution at 3000ppm.
We can now be sure to have a well saturated CDS.
Note: You will find other possibilities to perform this measurement in Tip # 8.
You can also estimate the concentration of CDS by its color.
- - = = = = = = = = - -Strip color scale.
Third saturation?
If by chance your CDS does not reach 3000ppm, don't panic, you can simply do a third saturation to reach 3000ppm, without having to start all over again. And even if your CDS is only 2000ppm it will still be effective, you just need to adjust the doses of use accordingly.
But stay alert because low saturation can also indicate a problem.
Examples:
a gas leak (there will be a smell of chlorine in the cupboard).
product solutions that are too low in concentration.
not enough solutions for the amount of water used.
Keep CDS
What CDS fears the most is Ultra Violet light. We will therefore keep this CDS (which I call mother tincture) in a dark bottle (amber) and preferably in the refrigerator, because the gas remains dissolved in water below 11°C.
It is preferable to divide the CDS into several small bottles rather than one large one, since this will allow not to open it too often, knowing that with each opening we will lose a little gas.
While you're at it, take a look at "Turbo Saturation"
which can come in handy for heavy CDS users.
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Feel free to click on this gray icon that appears when you hover over the image of the calculator to open the interactive version.
Or click on this link > Here <, it also works.