The carbonate ions, CO32- , represent the main active principle of soda and gives it its basic character.(in the present the word « soude » ,in French, refers to sodium hydroxide).
Experimental file
measure of the pH using pH paper and pHmeter : The solution has a pH=11, so that, its basic character is obvious.
Characterisation of the CO32- ions :
(first method) : action of the calcium chlorur. You get a precipitate of insoluble calcium carbonate according to the reaction :
Ca2++ CO32- -> CaCO3
(second method) : action of the concentrate chlohydric acid. You can notice an important emission of carbon dioxide, according to the reaction :
CO32-+ 2H+-> CO2 + H2O
We extracted iodine from the solution, through the action of Hydrogen Peroxide H2O2 in acid surrounding.
experimental File
Acidification of the solution using concentrated hydrochloric acid : The first result of the acidification of the solution is to let out carbon dioxide coming from carbonate ions.
Iodine is let out using hydrogen peroxide : The hydrogen peroxide oxidises iodide ions, iodine appears and turns the solution brown. One can also see a light precipitate of iodine.
Getting the gassy iodine to appear by heating the solution : a light heating lets out purple vapours of iodine.
Measuring the iodine : this experiment is part of the curriculum of the 1ere S form, so we asked them to measure the iodine in the solution. The iodine is measured with the thiosulphate of sodium. They found 1,29g of iodine in 100g of ash.
In the Landerneau area, two firms process seaweed for theit alginates. The Danisco firm has specialized in extracting alginic acid from raw seaweed. The Technature firm uses alginates to elaborate finished goods.
Danisco :
Mr Pasquier, the manager, conducted our guided tour of the factory. Every year the plant (9000 m2 of workshops and laboratories) processes 6000 tons of dried seaweed to produce 3000 tons of alginates.
The alginates supply numerous industries all over the world. Used as binders and thickeners, they can be found in inks, creams, glues, rubbers, toothpastes. As gelling agents they come in useful to make jams, custards, impression powders. These products ar marketed under the brand name SOBALG.
The Danisco firm provided us with a smal quantity of purified alginic acid so that we could study its properties. The danisco manager also explained to us a great length how they extract the alginates from the seaweed.
We conducted that experiment in our scholl laboratory.
Technature :
We were welcomed by the manager, Mr Le Fur, and the commercial manager, Mr Winckler (today manager of Lessonia). The firm packages the alginates for its different uses : casts, cosmetics, foodstuffs.
The firm has clients all over the world (Euope, the USA, Japan...). The breton products ar renowned for their quality and their purity.
The firm gave us some casting alginates so that we could make a cast.
They also offered us to elaborate a new "beauty mask". We will give more details about these two experiments in the following pages.
Technature entrusted us with the creation of a beauty mask. It is a new product the company wishes to launch. It’s a product made with tropical fruits, based on casting alginate.
The formula of the « tropical fruit » mask.
| Product used | Quantity | properties |
|---|---|---|
| Bioprunte (alginate of sodium, sulfate of calcium, salt of phosphorus, neutral charge of diatomees earth.) | 30g | When in close contact with the skin, it creates a film. The mask sets into action active agents, and also has a mechanical effect ( it eliminates the dead cells of the skin). |
Pinaple Pouder  Papaye powder | 0,15 g
| The cells of the skin are constantly replaced (every one to two months). With age, the process slows down, and the dead cells accumulate, which cause the skin to thicken. The dead cells are retained by a ciment of proteins ; it has to be hydrolysed to eliminate the dead cells. Papaye contains papaïn, an enzym, which acts on the hydrolysis of proteins. Pinaple contains bromeline which plays the same role. |
| yellow pigment n°5 yellow pigment n°6 | 0,03g
| Naturel pigments are used to obtain a pleasant colour of fruit. |
| Flavours : fruit de soleil, papaye | 0,015g | They are natural extracts from fruit, with very concentrated effects. |
First, we tested an alginate mask, with no additive, so as to watch the « casting » effect of that product.
We then tried several formulas, by varying the colours and flavours.
At last, we tested the resulting cast.
Dose : 30g of powder for 100g of water
Dilution of the product : Pour the water quickly on the powder. Mix briskly until you get a smooth paste.
Important : water must be at 20°C
How to apply it : Apply it immediately over the face, avoid the eyes. It sets after about six minutes.
It takes about 15 mn to use
Résult
your skin is finer
your complexion
brighter
Agar-Agar is a Malaysian word. That product used in Malaysia, was also often used in Japon and the Far East. Agar-Agar comes from various seaweed, in particular from the gelidum species. Those seaweed, after frequent washings, are dried and boiled. The colloid we get is then dehydrated and turned into powder.
Agar-agar has a stong gelling power. If you add two gramms into a quarter of a litre of water, and boil it for five minutes, you get a hard gel, if tou leave it to cool.
At the biology laboratory, Agar-Agar is used to prepare nutrient supports for plants.
At the chemistry laboratory, it can be used to prepare conducting electrolytic bridges in the study of batteries.
We prepared Agar-Agar colloid, coloured with helianthine. Agar-agar is also used to prepare pudding, but for that we used a seaweed from Brittany, Pioka, which contains carrageenans.
Agar-Agar : an excellent gelling agent extracted from red algae
Pioka is the Breton name of a seawweed that is also called sea « lichen ». It is collected at every low tide, its high price attracts seasonal pickers. Its scientific name is chondrus crispus. The active principle extracted from it is made up of carrageenans. It has a real gelling power in milk. In the traditionnal way, it is used by people along the Northern coast of Brittany to make puddings named « flans ».
The préparation of seaweeds.
After the gathering of seaweeds, they are spread on the dunes, and dried by often turning them. They can be also washed with fresh water to clear them of salt at various remains. At the end of treatment, the seaweeds are white and dry, and can then be preserved.
Just before use.
One can improve the rising process with several soakings ans rinsings. The seaweeds must completely get rid of their « sea » smell.
Seaweeds today, in food
We have prepared the recipe of this dessert. It was given to us by an elderly person from the Brignogan area in North-Finistere. She herself had seen her parents make it.
N.B : carrageenans of pioka easily give a gel with milk, it gives no gel with water. For that, on should use the agar-agar we also tested (it is also used for puddings).
Take a handful of dried seaweeds per quarter of a litre of milk. Rinse them. Make them boil for five minutes stirring them. Filter the hot milk with a strainer or a skimming ladle. Make it boil again for five minutes with the flavour choose, either chocolate or vanilla ( for exemple, three sponfils of Nesquick per quarter of litre of milk). Pour into bowls. Leave it cool and place it into a fridge.
When we started working on this project, we were not aware chemistry had been concerned with seaweed for so long.
We now, know, that here, people make products that are used all over the world.
Our impression is that the chemists who do that work really enjoy it, they extract from nature the best it can offer. The issue will be to increase the stock of seaweed and no doubt to plan its culture.
As far as our school project is concerned, it developed without our knowing it. The theorical study, the search for information, the experiments at the laboratory, the visit of factories, the elaboration of a new product, the test of an old recipe...all that was part of our project.
By writing this project, we intend to keep track of our work.
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