Chaufferette/en : Différence entre versions

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Some people really struggle to keep warm, and ski touring (to avoid the wasteful and environmentally-friendly ski lifts!) can become a real nightmare!  
 
Some people really struggle to keep warm, and ski touring (to avoid the wasteful and environmentally-friendly ski lifts!) can become a real nightmare!  
  
Some sports shops offer hand-heaters for a little extra comfort. These are small plastic containers that warm up to around 50°C when activated.
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Some sports shops offer hand-warmers for a little extra comfort. These are small plastic containers that warm up to around 50°C when activated.
  
 
Some are reusable, for around 20€ a pair, while others are not, for around 15€ for 30.
 
Some are reusable, for around 20€ a pair, while others are not, for around 15€ for 30.
  
In a complete low-tech approach, we should first ask ourselves about this need for comfort. But before we get there, and for those who may already have given this in-depth thought but still feel the need to have heaters, it's possible to make reusable (almost! See the discussion on the problems to be solved) and economical ones yourself (see the discussion on the problems to be solved). It's possible to make your own heaters that are reusable (almost! See discussion on the problems to be solved) and economical (that's confirmed!)!
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In a complete low-tech approach, we should first ask ourselves about this need for comfort. But before we get there, and for those who may already have given this in-depth thought but still feel the need to have warmers, it's possible to make reusable (almost! See the discussion on the problems to be solved) and economical ones yourself (see the discussion on the problems to be solved). It's possible to make your own warmers that are reusable (almost! See discussion on the problems to be solved) and economical (that's confirmed!)!
 
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{{Materials
 
{{Materials
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NB : La masse volumique du vinaigre est très proche de l'eau soit 1kg pour 1L.
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NB: The density of vinegar is very close to that of water, 1kg for 1L.
 
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{{Tuto Step
 
{{Tuto Step
|Step_Title=Nettoyage du matériel
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|Step_Title=Cleaning equipment
|Step_Content=Fabriquer des chaufferettes, c'est faire de la chimie, et la chimie n'aime pas trop les impuretés. Il est fortement conseillé de nettoyer correctement tout les ustensiles à l'eau et au savon. En particulier les contenant des chaufferettes au risque qu'il y reste un peu de compote si vous choisissez les mêmes que nous !
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|Step_Content=Making warmers involves doing chemistry, and chemistry doesn't take kindly to impurities. We strongly advise you to clean all utensils properly with soap and water. Particularly the containers of the warmers, as there's a risk of a little compote remaining in them if you choose the same ones as us!
 
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{{Tuto Step
 
{{Tuto Step
|Step_Title=Mélange des réactifs
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|Step_Title=Mixing reagents
|Step_Content='''Sécurité'''  
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|Step_Content='''Safety'''  
  
*Le vinaigre est une substance irritante pour la peau et fortement irritante pour les yeux. Ne pas hésiter à mettre des lunettes de protection lors du mélange. Autrement, faire attention au éclaboussure
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*Vinegar is irritating to the skin and very irritating to the eyes. Do not hesitate to wear safety goggles when mixing. Otherwise, watch out for splashes.
  
La première étape consiste à mélanger le vinaigre et le bicarbonate de sodium. Pour cela, on commence par verser la bonne quantité de vinaigre dans notre casserole. On vient en suite ajouter '''doucement''' le bicarbonate de sodium. Il faut en suite mélanger le tout jusqu'à ce qu'il n'y est plus de mousse. Cela indiquera que la réaction chimique est terminé.         
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The first step consists of mixing the vinegar and bicarbonate of soda. To do this, start by pouring the right amount of vinegar into the pan. Then add the bicarbonate of soda "slowly". Stir until there is no more foam. This indicates that the chemical reaction is complete.         
  
'''Point de vigilance'''  
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'''Point of vigilance'''  
  
*Verser doucement le bicarbonate de soude car la réaction produit du CO2 gazeux ce qui fait mousser la solution
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*Pour in the bicarbonate of soda slowly, as the reaction produces CO2 gas, causing the solution to foam.
*Cette étape prend du temps, mais mieux vaut aller au bout pour que l'ensemble du vinaigre réagisse. Si il reste du vinaigre, préparer vous à sentir son odeur nauséabonde lors de l'étape suivante !!
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*This stage takes time, but it's best to get to the end so that all the vinegar reacts. If there is any vinegar left over, be prepared to smell its nauseating odour during the next stage!
*Au plus on fabrique de chaufferette, au plus la réaction prendra du temps. Pour 5 chaufferette, on peut s'attendre à environs 20 min de mélange
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*The more warmers you make, the longer the reaction will take. For 5 warmers, you can expect about 20 minutes of mixing.
 
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{{Tuto Step
 
{{Tuto Step
|Step_Title=Chauffe, évaporation
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|Step_Title=Heating, evaporation
|Step_Content='''Sécurité'''
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|Step_Content='''Safety'''
  
*La substance obtenu par la réaction du vinaigre et du bicarbonate de sodium est de l'éthanoate de sodium. Cette substance est irritante, ne pas hésiter à porter des lunettes de sécurité. Autrement, prenez garde à ne pas vous en mettre dans les yeux
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*The substance obtained from the reaction of vinegar and sodium bicarbonate is sodium ethanoate. This substance is irritating, so don't hesitate to wear safety goggles. Otherwise, be careful not to get any in your eyes.
*Léger risque de brûlure, potentielle petite projection en cas de grosse quantité et de plaque de cuisson de forte puissance
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*Slight risk of burns, possible small splashes if large quantities are used on a high-powered hob.
  
Lorsque la première étape est bien terminé, on peut mettre notre casserole à chauffer à feu vif, l'objectif est de faire s'évaporer toute l'eau qu'il y a en trop. Je dis en trop, car nous aurons besoin d'un petit peu d'eau pour obtenir la bonne substance.  Lorsqu'un film très léger commence à apparaitre à la surface, alors la substance est prête, il faut arrêter la chauffe.  
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When the first stage is complete, we can put our saucepan on a high heat, the aim being to evaporate all the excess water. I say too much, because we'll need a little more water to get the right substance.  When a very light film begins to appear on the surface, then the substance is ready, you need to stop heating.  
  
  
'''Point de vigilance'''  
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'''Point of vigilance'''  
  
*Il y a une grande quantité d'eau à évaporer donc cette étape prend un certain temps (encore une fois, au plus on fait de chaufferette, au plus l'évaporation est longue)
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*There's a lot of water to evaporate, so this stage takes a while (again, the more warmers you use, the longer it takes to evaporate).
*Lors de cette étape il ne se passera rien pendant longtemps, mais à la fin tout va très vite. Il faut donc être très attentif dès lors que le liquide se trouble très légèrement et jauni.
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*During this stage, nothing happens for a long time, but in the end everything happens very quickly. You need to be very careful as soon as the liquid becomes slightly cloudy and yellow.
*Généralement, sur la fin, des cristaux apparaitrons sur les bords de la casseroles.
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*Generally, crystals will appear on the edges of the pan towards the end.
*Si par mégarde, on laisse le liquide trop longtemps chauffer, il se solidifie complétement. Dans ce cas, couper le feu et ajouter de l'eau rapidement (pas en trop grande quantité, juste assez pour voir '''tout le solide redevenir liquide'''). On peut en suite le remettre sur le feu en remuant pour aider les dernier cristaux à ce liquéfier. Pas d'inquiétude, les chaufferettes fonctionneront tout de même !
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*If you inadvertently leave the liquid to heat for too long, it will solidify completely. In this case, turn off the heat and add water quickly (not too much, just enough to see all the solid become liquid again). You can then put it back on the heat, stirring to help the last crystals liquefy. Don't worry, the warmers will still work!
*Vers la fin une odeur proche de celle d'un gâteau au four devrait apparaitre. Elle n'est pas désagréable mais éviter de trop la renifler !! Mieux vaut être prudent lorsque l'on joue à l'apprenti chimiste ! Même lorsque l'on manipule des substances peu dangereuse :)
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*Towards the end, a smell similar to that of a baked cake should appear. It's not unpleasant, but avoid sniffing it too much! It's best to be careful when playing chemist's apprentice! Even when you're handling substances that aren't very dangerous :)
 
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{{Tuto Step
 
{{Tuto Step
|Step_Title=Remplissage
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|Step_Title=Filling
|Step_Content='''Sécurité'''
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|Step_Content='''Safety'''
  
*Risque de brûlure, le liquide à verser dans les contenants de chaufferettes est très chaud (environs 100°C au début)
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*Risk of burns, as the liquid to be poured into the warmer containers is very hot (around 100°C at first).
*En cas de contact avec la peau à moins de 60°C, le liquide se solidifiera et ce réchauffera. C'est très impressionnant car le solide colle à la peau. Pas de panique, un peu d'eau et il partira tout seul. Ne tardez tout de même pas trop à rincer à l'eau pour éviter une brûlure.
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*If the liquid comes into contact with the skin at less than 60°C, it will solidify and heat up. It's very impressive because the solid sticks to the skin. Don't panic, a little water and it will go away on its own. However, don't take too long to rinse off with water to avoid burning yourself.
 
   
 
   
L'objectif de cette étape est de remplir les contenants de nos chaufferettes par la substance obtenu à l'étape 4.   
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The aim of this step is to fill the containers of our warmers with the substance obtained in step 4.   
  
Il faut être deux pour cette étape, seul il est difficile de tenir les contenant et de verser en même temps.   
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Two people are needed for this stage, as it is difficult to hold the containers and pour at the same time.   
  
La personne qui tien le contenant peut mettre des gants pour limiter le risque de brûlure.   
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The person holding the container can wear gloves to limit the risk of burns.   
  
Dans cette étape on utilise un entonnoir que l'on vient insérer dans les contenants, puis on vient verser le contenu de la casserole doucement.
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At this stage, a funnel is inserted into the containers and the contents of the saucepan are poured in gently.
  
  
'''Point de vigilance'''  
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'''Point of vigilance'''  
  
*Il faut laisser une petite entré d'air dans la chaufferette lorsque l'on verse le liquide, prenez garde à ne pas complétement boucher le trou avec l'entonnoir au risque de débordement et donc de brûlure :(
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*Leave a small air space in the warmer when pouring in the liquid. Be careful not to completely block the hole with the funnel, as this could cause the liquid to overflow and burn :(
*Entre chaque chaufferettes, remuer la casserole pour mélanger le liquide et éviter que la surface ne se solidifie
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*Between each warmers, stir the pan to mix the liquid and prevent the surface from solidifying.
*Le liquide se solidifie au alentour de 58°C, il faut donc le verser avant qu'il n'atteigne cette température, autrement l'entonnoir sera bouché. N'y allez pas pour autant trop vite au risque de vous bruler. Si la substance commence à trop refroidir, il suffi d'y ajouter un petit peu d'eau et de réitérer l'étape 4.
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*The liquid solidifies at around 58°C, so pour it in before it reaches this temperature, otherwise the funnel will be blocked. However, don't pour too quickly or you could get burnt. If the substance starts to cool too much, simply add a little water and repeat step 4.
*Si l'entonnoir est complétement boucher, vous pouvez y verser de l'eau chaude, le solide deviendra liquide rapidement est coulera à flot !
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*If the funnel is completely blocked, you can pour in some hot water and the solid will quickly become liquid and flow!
 
|Step_Picture_00=Chaufferette_1707570183965.jpg
 
|Step_Picture_00=Chaufferette_1707570183965.jpg
 
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{{Tuto Step
 
{{Tuto Step
|Step_Title=Recharge des chaufferettes
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|Step_Title=Reloading warmers
|Step_Content=Les chaufferettes sont maintenant prête à être charger !
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|Step_Content=The warmers are now ready to be loaded!
  
  
Afin de charger en chaleur les chaufferettes, il faut les mettre dans de l'eau bouillante durant 10-15min. Ensuite, on doit les laisser refroidir sans trop les remuer jusqu'à qu'elle soit à température ambiante.  
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To charge the warmers with heat, place it in boiling water for 10-15 minutes. Then leave them to cool, without stirring them too much, until they reach room temperature.  
  
Elles sont maintenant pleine d'énergie et prête pour utilisation en montagne ou ailleurs !
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They're now full of energy and ready for use in the mountains or anywhere else!
  
 
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{{Tuto Step
 
{{Tuto Step
|Step_Title=Utilisation des chaufferettes
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|Step_Title=Use of warmers
|Step_Content=Une fois en pleine montagne dans le froid, on peut les activer, pour cela il faut suivre la notice.  
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|Step_Content=Once you're out in the mountains in the cold, you can activate them by following the instructions.  
  
Elle chauffe alors jusqu'à environs 50°C. Pour conserver la chaleur créer, il est conseillé de les isoler de l'air extérieur en les mettant dans vos gants et/ou dans vos poches.
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It then heats up to around 50°C. To keep the heat created, it is advisable to isolate them from the outside air by putting them in your gloves and/or pockets.
  
  
'''Sécurité'''
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'''Safety'''
  
Attention, il est '''fortement déconseillé de réchauffer brutalement une engelure.''' L'utilisation des chaufferettes se veut '''préventive''', pour prévenir de forte sensation de froid et non pour réchauffer une zone en état critique.
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Warning: it is '''strongly inadvisable to heat up a frostbite suddenly'''. The use of warmers is ''preventive'', to prevent a strong sensation of cold and not to heat an area in critical condition.
  
En suite, il est fortement déconseillé d'alterner chaud et froid sur une engelure. Mieux vos privilégier des vêtements secs et attendre un bain thermostaté à 37°C une fois en lieu sûr.
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Then, it is not advisable to alternate between hot and cold for frostbite. It's better to wear dry clothes and wait for a bath thermostated at 37°C once you're in a safe place.
  
  
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{{Tuto Step
 
{{Tuto Step
|Step_Title=La théorie des chaufferettes
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|Step_Title=The theory of warmers
|Step_Content=Il a été très intéressant pour moi d'expérimenter par moi même et d'améliorer un procéder suite à des observation personnels ! Je vous fais ici part de mes découvertes tiré de mes expériences et de mes lectures.
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|Step_Content=It's been very interesting for me to experiment and improve a process following personal observations! I share with you my discoveries from my experiences and my readings.
  
===Fabrication de l'éthanoate de sodium, réaction chimique===
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===Manufacture of sodium ethanoate, chemical reaction===
L'éthanoate de sodium est un produit de la réaction entre l'acide éthanoïque et le bicarbonate de sodium.
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Sodium ethanoate is a product of the reaction between ethanoic acid and sodium bicarbonate.
  
Cette réaction produit aussi de l'eau est du CO2.  
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This reaction also produces water and CO2.  
====Calcule des quantités====
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====Calculating quantities====
Cette partie n'est pas très fun, à passer si vous n'êtes pas un grand fan de calculs de chimie ! Mais nécessaire si vous voulez recalculer le tout par vous même !
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This part isn't much fun, so skip it if you're not a big fan of chemistry calculations! But it is necessary if you want to recalculate everything yourself!
  
Afin de déterminer les quantités d'acide éthanoïque et de bicarbonate de soude à mélanger on fait l'hypothèse que la réaction est totale. Ainsi, afin d'optimiser le tout, il faut mélanger les réactifs en quantité dite stœchiométriqueLorsqu'on insère exactement ces quantités, tout les réactifs sont consommé et il ne reste plus que des produit à la fin de la réaction!
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To determine the quantities of ethanoic acid and sodium bicarbonate to mix, we assume that the reaction is complete. So, in order to optimise everything, we need to mix the reagents in what are known as stoichiometric quantitiesWhen you add exactly these quantities, all the reagents are consumed and all that's left at the end of the reaction is the product!
  
Dans notre cas, une molécule d'acide éthanoïque réagit avec une molécule de bicarbonate de sodium. Ainsi, il faut mettre le même nombre de "quantité de matière" (de moles) de chacun des deux réactifs afin d'atteindre les quantités stœchiométriques.  
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In our case, one molecule of ethanoic acid reacts with one molecule of sodium bicarbonate. The same number of "quantities of matter" (moles) of each of the two reagents must therefore be added in order to reach the stoichiometric quantities.  
  
Sachant cela, on calcul la quantité de matière correspondante à 35g de bicarbonate (pour 1 chaufferette).  
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Knowing this, calculate the quantity of material corresponding to 35g of bicarbonate (for 1 warmer).  
  
En suite, on calcul la masse d'acide acétique pour obtenir exactement la même quantité de matière (ce qui dépendra de sa masse molaire).
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Next, calculate the mass of acetic acid needed to obtain exactly the same quantity of substance (which will depend on its molar mass).
  
Enfin, sachant qu'un vinaigre, disons, à 8%, possède 0,08 g d'acide éthanoïque pour 100mL, alors on calcul le volume de vinaigre pour obtenir exactement la bonne masse d'acide éthanoïque.
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Finally, knowing that, say, 8% vinegar has 0.08g of ethanoic acid per 100mL, we calculate the volume of vinegar to obtain exactly the right mass of ethanoic acid.
  
Si on préfère, il est possible de calculer la masse de vinaigre plutôt que son volume (Utile lorsque l'on a pas de verre doseur). Par chance, le vinaigre à presque la masse volumique de l'eau, donc 1kg de vinaigre pour 1l de vinaigre.
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If you prefer, you can calculate the mass of vinegar rather than its volume (useful if you don't have a measuring glass). Luckily, vinegar has almost the same density as water, so 1kg of vinegar for 1l of vinegar.
  
  
Il a de nombreuse ressource pédagogique sur les calculs de base en chimie des solution sur internet si cela vous intéresse. Ce sont des notions aborder en début de lycée en France.   
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There are a number of educational resources on basic calculations in solution chemistry on the internet if you're interested. This is a subject that is covered at the beginning of secondary school in France.   
  
 
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====Comprendre par ses propres sens====
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====Understanding with your own senses====
Cette réaction est amusante à expérimenter car très visuel, la production de CO2 gazeux produit de la mousse. On peu alors savoir si toute nos molécules on bien réagi.  
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This reaction is fun to experiment with because it is very visual: the production of gaseous CO2 produces foam. We can then see whether all our molecules have reacted properly.  
 
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====Pourquoi la réaction (mélange) est si longue ?====
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====Why does the reaction (mixing) take so long? ====
La réaction prend du temps, et on est obligé de mélanger ! Mais que se passe-t-il dans le monde des molécules pour que cela prenne autant de temps !  
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The reaction takes time, and we have to mix! But what happens in the world of molecules to make it take so long!  
  
Dans notre casserole après quelques seconde de réaction, on a beaucoup d'eau, des réactifs mais aussi les quelques produits déjà créer. Pour pouvoir réagir, il faut que deux molécules de réactif se rencontre.  
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In our saucepan, after a few seconds of reaction, we have a lot of water, the reactants and also the few products that have already been created. In order to react, two molecules of reagent must meet.  
  
Mais comment ce rencontrer dans tout ce bazar !? C'est un peu comme si on jetait du pollen dans un champs de fleur, au début, il est facile pour le pollen de trouver une fleur célibataire, mais après quelques minutes, lorsque de nombreux couple se sont former, difficile pour une petite fleur et un pollen de ce retrouver.  
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But how do you meet someone in this mess? It's a bit like throwing pollen into a field of flowers, at first it's easy for the pollen to find a single flower, but after a few minutes, when many couples have formed, it's difficult for a small flower and a pollen to find each other.  
  
En terme technique on parle de '''cinétique de réaction''' pour désigner la vitesse à laquelle elle à lieu et de '''phénomène limitant''' pour parler du phénomène qui impose cette vitesse.  
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In technical terms, we speak of '''reaction kinetics''' to refer to the speed at which the reaction takes place and of '''limiting phenomenon''' to refer to the phenomenon that imposes this speed.  
  
Ici c'est la rencontre des molécules qui est la plus lente, on parle donc de '''transfert de masse'''. <br />
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Here it is the meeting of the molecules that is the slowest, so we speak of ''mass transfer''. <br />.
  
====Vous avez dit cristallisation ?====
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====Did you say crystallisation? ====
On a déjà discuter du problème de cristallisation si on fait chauffer trop longuement le liquide. C'est assez contre-intuitif comme observation. Normalement, en augmentant la température, on passe de solide à liquide pas l'inverse.  
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We've already discussed the problem of crystallisation if the liquid is heated for too long. This is a rather counter-intuitive observation. Normally, by increasing the temperature, you go from solid to liquid, not the other way round.  
  
Le phénomène de cristallisation provient ici de la déshydratation l'éthanoate de sodium trihydraté vers l'éthanoate de sodium anhydre. En faite, la substance '''trihydraté''', celle que l'on souhaite pour nos chaufferette, se liquéfie si on la chauffe au delà de '''58°C'''. En revanche, la substance '''anhydre''' elle ne se liquéfie qu'à '''324°C'''. Ainsi, lorsqu'on enlève son eau à une molécule, PAF ! Elle devient anhydre et se solidifie instantanément car nous ne somme bien en dessous de 324°C !
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The phenomenon of crystallisation comes from the dehydration of sodium ethanoate trihydrate to anhydrous sodium ethanoate. In fact, the '''trihydrate''' substance, the one we want for our warmers, liquefies if we heat it above '''58°C'''. On the other hand, the '''anhydrous''' substance only liquefies at '''324°C'''. So when you remove the water from a molecule, PAF! It becomes anhydrous and solidifies instantly, because we're well below 324°C!
  
  
Au début, il y a de l''''eau en excès''', donc c'est cette eau la qui s'évapore. Mais dès lors qu'il n'y a presque plus d'eau, on commence à '''déshydrater''' nos bonne vieille molécule, '''d'où l'apparition sur la fin de cristaux''', puis, progressivement '''d'un film solide'''.  
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At the beginning, there's an '''excess of water''', so it's this water that evaporates. But as soon as there is almost no water left, we start to '"dehydrate'" our good old molecule, "'hence the appearance at the end of crystals'", then, progressively '"a solid film'".  
 
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====Comprendre pour mieux agir !====
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====Understand to act more effectively!====
Ici, la connaissance du phénomène permet de juger quand arrêter l'étapes 4. En effet, à l'apparition des premiers cristaux, on sait que le liquide restant n'est pas de l'eau mais bien de l'éthanoate de sodium trihydraté, car si il y avait encore de l'eau liquide, c'est elle qui s'évaporerais et aucun cristaux n'apparaitrais !<br />
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Here, knowing the phenomenon allows you to judge when to stop step 4: when the first crystals appear, you know that the remaining liquid is not water but sodium ethanoate trihydrate, because if there was still liquid water, it would evaporate and no crystals would appear!<br />.
  
===Le plus important ! Pourquoi les chaufferettes chauffe !===
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===The most important thing! Why warmers heat up!===
Le fonctionnement des chaufferettes se base sur le phénomène de surfusion ! Pour en savoir plus vous pouvez consulter cette article :
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Warmers work on the basis of the phenomenon of supercooling! To find out more, read this article:
  
 
https://ssaft.com/Blog/dotclear/?pages/Acetate-de-Sodium
 
https://ssaft.com/Blog/dotclear/?pages/Acetate-de-Sodium
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{{Tuto Step
 
{{Tuto Step
|Step_Title=Problématique non résolue
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|Step_Title=Unresolved issue
|Step_Content====Des chaufferettes presque réutilisable !===
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|Step_Content====The warmers are almost reusable!===
Les chaufferettes devrait être réutilisable en théorie. Dans la réalité, à chaque nouvelle utilisation il devient plus difficile de les activer. Je n'ai pas su percé le mystère de ce phénomène mais peut être que vous y arriverez !  
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In theory, warmers should be reusable. In reality, each time they are used it becomes more difficult to activate them. I haven't been able to solve the mystery of this phenomenon, but maybe you can!  
  
  
Elles sont tout de même réutilisable un certain nombre de fois si on accepte d'attendre un peu et de s'y reprendre à plusieurs fois pour les activer.  
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They can be reused a number of times, however, if you are prepared to wait a while and go over them several times to activate them.  
  
  
Pour les plus persistant, en insérant un tige en métal et en la malaxant l'activation est plus efficace donc vous pourrez les réutiliser plus longtemps avec cette méthode. Pour se faire vous pouvez insérer un l'embout d'un petit tourne vis, d'une vis ou tout objet métallique, le malaxer pendant un certain temps et le retirer une fois que la chaufferette se met à chauffer :)
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For the more persistent, inserting a metal rod and kneading it will activate it more effectively, so you'll be able to reuse it for longer with this method. To do this, you can insert the tip of a small screwdriver, a screw or any metal object, knead it for a while and remove it once the heater starts to heat up :)
 
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===Quelques auto-activations imprévues===
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===Some unexpected auto-activations===
Parfois, pendant la recharge, après les avoirs fait chauffer et une fois au repos. Les chaufferettes peuvent s'activer toute seul. Cela peut être embêtant car il faut alors les remettre à charger.
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Sometimes during recharging, after having warmed them up and once at rest. The warmers may activate by themselves. This can be annoying because you then have to charge them again.
  
Pour s'assurer qu'une chaufferette est bien prête à utilisation il faut simplement vérifier qu'elle soit bien liquide. Si c'est le cas vous êtes sûr de votre coup.
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To be sure that a heater is ready to use, simply check that it is liquid. If it is, you're on the safe side.
 
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Version actuelle datée du 2 juillet 2024 à 16:43

Tutorial de avatarLow-tech with Refugees - Low-tech & Réfugiés | Catégories : Outils

Introduction

When we go out in the mountains, we sometimes find ourselves exposed to the cold, particularly on the extremities of the body (hands, feet).

Some people really struggle to keep warm, and ski touring (to avoid the wasteful and environmentally-friendly ski lifts!) can become a real nightmare!

Some sports shops offer hand-warmers for a little extra comfort. These are small plastic containers that warm up to around 50°C when activated.

Some are reusable, for around 20€ a pair, while others are not, for around 15€ for 30.

In a complete low-tech approach, we should first ask ourselves about this need for comfort. But before we get there, and for those who may already have given this in-depth thought but still feel the need to have warmers, it's possible to make reusable (almost! See the discussion on the problems to be solved) and economical ones yourself (see the discussion on the problems to be solved). It's possible to make your own warmers that are reusable (almost! See discussion on the problems to be solved) and economical (that's confirmed!)!

Matériaux

  • Sodium bicarbonate (baking soda)
  • Vinegar
  • Container for warmers (here empty compotes to take away)

The quantities will be discussed in the tutorial as they depend on the concentration of the vinegar.

Outils

  • Saucepan
  • Scales
  • Spoon
  • Funnel
  • Glass
  • Measuring glass

Étape 1 - Calculating quantities

Here are the quantities for one warmer ! The mass of vinegar depends on its concentration.

Quantity for one warmer

35g baking soda

Concentration of vinegar [%] [g Mass of vinegar [g] Approximate volume of vinegar [mL
6 415 415
8 315 315
10 250 250
12 210 210
14 180 180
16 155 155

These values are approximate. You can find out how to calculate them in the theoretical sections.


NB: The density of vinegar is very close to that of water, 1kg for 1L.

Étape 2 - Cleaning equipment

Making warmers involves doing chemistry, and chemistry doesn't take kindly to impurities. We strongly advise you to clean all utensils properly with soap and water. Particularly the containers of the warmers, as there's a risk of a little compote remaining in them if you choose the same ones as us!

Étape 3 - Mixing reagents

Safety

  • Vinegar is irritating to the skin and very irritating to the eyes. Do not hesitate to wear safety goggles when mixing. Otherwise, watch out for splashes.

The first step consists of mixing the vinegar and bicarbonate of soda. To do this, start by pouring the right amount of vinegar into the pan. Then add the bicarbonate of soda "slowly". Stir until there is no more foam. This indicates that the chemical reaction is complete.

Point of vigilance

  • Pour in the bicarbonate of soda slowly, as the reaction produces CO2 gas, causing the solution to foam.
  • This stage takes time, but it's best to get to the end so that all the vinegar reacts. If there is any vinegar left over, be prepared to smell its nauseating odour during the next stage!
  • The more warmers you make, the longer the reaction will take. For 5 warmers, you can expect about 20 minutes of mixing.


Étape 4 - Heating, evaporation

Safety

  • The substance obtained from the reaction of vinegar and sodium bicarbonate is sodium ethanoate. This substance is irritating, so don't hesitate to wear safety goggles. Otherwise, be careful not to get any in your eyes.
  • Slight risk of burns, possible small splashes if large quantities are used on a high-powered hob.

When the first stage is complete, we can put our saucepan on a high heat, the aim being to evaporate all the excess water. I say too much, because we'll need a little more water to get the right substance. When a very light film begins to appear on the surface, then the substance is ready, you need to stop heating.


Point of vigilance

  • There's a lot of water to evaporate, so this stage takes a while (again, the more warmers you use, the longer it takes to evaporate).
  • During this stage, nothing happens for a long time, but in the end everything happens very quickly. You need to be very careful as soon as the liquid becomes slightly cloudy and yellow.
  • Generally, crystals will appear on the edges of the pan towards the end.
  • If you inadvertently leave the liquid to heat for too long, it will solidify completely. In this case, turn off the heat and add water quickly (not too much, just enough to see all the solid become liquid again). You can then put it back on the heat, stirring to help the last crystals liquefy. Don't worry, the warmers will still work!
  • Towards the end, a smell similar to that of a baked cake should appear. It's not unpleasant, but avoid sniffing it too much! It's best to be careful when playing chemist's apprentice! Even when you're handling substances that aren't very dangerous :)



Étape 5 - Filling

Safety

  • Risk of burns, as the liquid to be poured into the warmer containers is very hot (around 100°C at first).
  • If the liquid comes into contact with the skin at less than 60°C, it will solidify and heat up. It's very impressive because the solid sticks to the skin. Don't panic, a little water and it will go away on its own. However, don't take too long to rinse off with water to avoid burning yourself.

The aim of this step is to fill the containers of our warmers with the substance obtained in step 4.

Two people are needed for this stage, as it is difficult to hold the containers and pour at the same time.

The person holding the container can wear gloves to limit the risk of burns.

At this stage, a funnel is inserted into the containers and the contents of the saucepan are poured in gently.


Point of vigilance

  • Leave a small air space in the warmer when pouring in the liquid. Be careful not to completely block the hole with the funnel, as this could cause the liquid to overflow and burn :(
  • Between each warmers, stir the pan to mix the liquid and prevent the surface from solidifying.
  • The liquid solidifies at around 58°C, so pour it in before it reaches this temperature, otherwise the funnel will be blocked. However, don't pour too quickly or you could get burnt. If the substance starts to cool too much, simply add a little water and repeat step 4.
  • If the funnel is completely blocked, you can pour in some hot water and the solid will quickly become liquid and flow!




Étape 6 - Reloading warmers

The warmers are now ready to be loaded!


To charge the warmers with heat, place it in boiling water for 10-15 minutes. Then leave them to cool, without stirring them too much, until they reach room temperature.

They're now full of energy and ready for use in the mountains or anywhere else!


Étape 7 - Use of warmers

Once you're out in the mountains in the cold, you can activate them by following the instructions.

It then heats up to around 50°C. To keep the heat created, it is advisable to isolate them from the outside air by putting them in your gloves and/or pockets.


Safety

Warning: it is strongly inadvisable to heat up a frostbite suddenly. The use of warmers is preventive, to prevent a strong sensation of cold and not to heat an area in critical condition.

Then, it is not advisable to alternate between hot and cold for frostbite. It's better to wear dry clothes and wait for a bath thermostated at 37°C once you're in a safe place.






Étape 8 - The theory of warmers

It's been very interesting for me to experiment and improve a process following personal observations! I share with you my discoveries from my experiences and my readings.

Manufacture of sodium ethanoate, chemical reaction

Sodium ethanoate is a product of the reaction between ethanoic acid and sodium bicarbonate.

This reaction also produces water and CO2.

Calculating quantities

This part isn't much fun, so skip it if you're not a big fan of chemistry calculations! But it is necessary if you want to recalculate everything yourself!

To determine the quantities of ethanoic acid and sodium bicarbonate to mix, we assume that the reaction is complete. So, in order to optimise everything, we need to mix the reagents in what are known as stoichiometric quantities. When you add exactly these quantities, all the reagents are consumed and all that's left at the end of the reaction is the product!

In our case, one molecule of ethanoic acid reacts with one molecule of sodium bicarbonate. The same number of "quantities of matter" (moles) of each of the two reagents must therefore be added in order to reach the stoichiometric quantities.

Knowing this, calculate the quantity of material corresponding to 35g of bicarbonate (for 1 warmer).

Next, calculate the mass of acetic acid needed to obtain exactly the same quantity of substance (which will depend on its molar mass).

Finally, knowing that, say, 8% vinegar has 0.08g of ethanoic acid per 100mL, we calculate the volume of vinegar to obtain exactly the right mass of ethanoic acid.

If you prefer, you can calculate the mass of vinegar rather than its volume (useful if you don't have a measuring glass). Luckily, vinegar has almost the same density as water, so 1kg of vinegar for 1l of vinegar.


There are a number of educational resources on basic calculations in solution chemistry on the internet if you're interested. This is a subject that is covered at the beginning of secondary school in France.


Understanding with your own senses

This reaction is fun to experiment with because it is very visual: the production of gaseous CO2 produces foam. We can then see whether all our molecules have reacted properly.

Why does the reaction (mixing) take so long?

The reaction takes time, and we have to mix! But what happens in the world of molecules to make it take so long!

In our saucepan, after a few seconds of reaction, we have a lot of water, the reactants and also the few products that have already been created. In order to react, two molecules of reagent must meet.

But how do you meet someone in this mess? It's a bit like throwing pollen into a field of flowers, at first it's easy for the pollen to find a single flower, but after a few minutes, when many couples have formed, it's difficult for a small flower and a pollen to find each other.

In technical terms, we speak of reaction kinetics to refer to the speed at which the reaction takes place and of limiting phenomenon to refer to the phenomenon that imposes this speed.

Here it is the meeting of the molecules that is the slowest, so we speak of mass transfer.
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Did you say crystallisation?

We've already discussed the problem of crystallisation if the liquid is heated for too long. This is a rather counter-intuitive observation. Normally, by increasing the temperature, you go from solid to liquid, not the other way round.

The phenomenon of crystallisation comes from the dehydration of sodium ethanoate trihydrate to anhydrous sodium ethanoate. In fact, the trihydrate substance, the one we want for our warmers, liquefies if we heat it above 58°C. On the other hand, the anhydrous substance only liquefies at 324°C. So when you remove the water from a molecule, PAF! It becomes anhydrous and solidifies instantly, because we're well below 324°C!


At the beginning, there's an excess of water, so it's this water that evaporates. But as soon as there is almost no water left, we start to '"dehydrate'" our good old molecule, "'hence the appearance at the end of crystals'", then, progressively '"a solid film'".

Understand to act more effectively!

Here, knowing the phenomenon allows you to judge when to stop step 4: when the first crystals appear, you know that the remaining liquid is not water but sodium ethanoate trihydrate, because if there was still liquid water, it would evaporate and no crystals would appear!
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The most important thing! Why warmers heat up!

Warmers work on the basis of the phenomenon of supercooling! To find out more, read this article:

https://ssaft.com/Blog/dotclear/?pages/Acetate-de-Sodium

Étape 9 - Unresolved issue

The warmers are almost reusable!

In theory, warmers should be reusable. In reality, each time they are used it becomes more difficult to activate them. I haven't been able to solve the mystery of this phenomenon, but maybe you can!


They can be reused a number of times, however, if you are prepared to wait a while and go over them several times to activate them.


For the more persistent, inserting a metal rod and kneading it will activate it more effectively, so you'll be able to reuse it for longer with this method. To do this, you can insert the tip of a small screwdriver, a screw or any metal object, knead it for a while and remove it once the heater starts to heat up :)

Some unexpected auto-activations

Sometimes during recharging, after having warmed them up and once at rest. The warmers may activate by themselves. This can be annoying because you then have to charge them again.

To be sure that a heater is ready to use, simply check that it is liquid. If it is, you're on the safe side.

Notes et références

Noé Beaupere. PILOTAGE DE LA LIBÉRATION DE CHALEUR ET ÉTUDE DU VIEILLISSEMENT DE MATÉRIAUX À CHANGEMENT DE PHASE. Sciences de l’ingénieur [physics]. Université d’Artois, 2019. Français. https://theses.hal.science/tel-03160528

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