Ice Baths

[disarmme]

i'm new to pyrotechnics (and also to chemistry in general) and i'm the kind of person who wants to do things EXACTLY right. i've noticed alot of projects require a "salt-ice bath". i know basically what that is, but i was wondering if there was any precise method and measurements that must be used. i'd liked to hear everyone's personal method as well. sorry it's a dumb question, but that what the water cooler is for i guess. newbies. thanks.

[rooster]

What is the best form of ice bath you guys have made with OTC chemicals?
By "the best" I mean for nitrations (or other exothermic reactions).
I am not looking for what you normally use, but what you have had the best effect with.

Is the one with NH4NO3, NH4Cl and water stronger than the one with just NH4NO3 and water?

Also I read that CaCl2 x XH2O is endohtermic in reaction with water. Maybe this could be used?

The regualr one with NaCl, ice and water seems uneffective.
I know of the one with acetone and dry ice that is fucking cold. The reactions will likely stop or be slowed too much down if not the reaction is VERY exothermic. Anyways, dry ice is not too easy to come by is it?

What are your best ice baths?

[yt2095]

disarmme,

the fact is, that for PYRO ice baths are rarely to never needed, in fcat a ball mill will be your most used peice of kit along with seives of various mesh widths.
ice + salt (NaCl) and bit of water makes a freezing mix from regualr ice, takes the temp down to about -7(ish).
that`s usualy used for HI-EX or crystalisation of a difficult solution or weak solution to cyrystalise in PYRO.
reducing the water content by evaporation is usualy sufficient for crystalisation in pyro.
the odd exception is for deliquescent or efflorescent (sp?) chems that make require active drying, they are rarely used in PYRO anyway :)

a search here will tell you ALOT more than i`m likely to in a single post :)

All the best :)

[knowledgehungry]

Dry ice is very easy to come by, look for it in the phone book. Ice cream places sell it.

[kingspaz]

i find ammonium nitrate and ice works quite well. gets a nice chill going. also to improve perfromace of an ice bath rest it on a polystyrene sheet (insulator) of about 2cm thick to reduce heat flow into the ice bath from the work bench. also wrap it in foil to reflect the infra red radiation coming from other objects in the room. that should increase the lifespan of the icebath. i find it annoying when it begins to run out halfway through a reaction.

[ALENGOSVIG1]

Ive read that CaCl2 ice baths can reach -20 to -30, and that NaCl ice baths can reach -10.

Remember, its important that the ice is well crushed.

What are you preparing that needs this kind of an ice bath?

[disarmme]

thanks for the correction yt2095. now that i think about it you're very right. i've been interested in pyro and HE's, and it's true that they don't use it much in pyro. i wasn't thinking. is there a real term for working with HE's? they have "pyrotechnics" of course (i know it's alot different from HE's), i was just wondering if there was an official term for working with HE's. i have alot to learn. i hope i can learn alot from you guys at The Forum. thanks for the info (and honesty).

[grendel23]

A cooling bath can range from a half liter of water with a few ice cubes floating in it, to a container of crushed ice with rock salt or NH4NO3 added to lower the temperature, to a jacketed reaction vessel with dry ice cooled acetone in the jacket.
I think what is more important is to understand the "why" things are done the way they are. If a reaction is exothermic and must be kept at a certain temperature, you can try with a very small amount of reactants and see for yourself how robust your cooling must be. When you have a handle on the small reaction, scale up slowly, larger amounts are much more difficult to cool.
This is a good idea for all unfamiliar reactions, start small because unexpected events will be less dangerous.

[kingspaz]

disarmme, i recomend you learn as much chemistry as you can whilst reading your way through the threads of the forum and its archives. try and find some beginner chemistry sites to get you into the basics. the basics are what you must not forget as chemistry will always come back to them.

[blindreeper]

-20 to - 30 seems off because when ever I have made a solution of CaCl2 it gets hot, I think thats one of the reasons it's used as ice melter. Or maybe once it cools down it can go to those temperatures :rolleyes:

[knowledgehungry]

CaCl2 may indeed be exothermic when dissolved in H2O, but it cools it down when added to ice. I dont feel like explaining BP changes and the effect of that on a solution but suffice it to say that when ice melts it cools the surrounding area.

[0EZ0]

When I wish to keep my beverages nice and cold, I use a pre chilled CaCl2 ice bath. Works wonders, and stays nice and icy cold:). NH4NO3 cooling baths have the advantage that you can prepare a bath on-site (vacation;)) without prior chilling of the cooling mix. Even when this mix is spent and starts to warm to room temp, the mix can be placed into a freezer and re-cooled. Since dissolving NH4NO3 in water also lowers the freezing point, it can be re-used like this as a salt/ice bath mix. There are many alternatives to using salt/ice as a cooling mix. Think of glycols, volitile solvents, dry ice mixes, etc.

Most salt/ice baths work on the principle that with the salt disolved in the water, the freezing point of the mixture becomes lower. With a lower freezing point, the mix can be very cold while still retaining most of it's liquid properties. Liquids conduct temperature better than granulated ice, giving better cooling.

So obviously if you want the most efficient cooling, you would want a cooling mix that stays liquid even at relatively low temperatures(-25 to -50). If that can be achieved, then you can seal the liquid in a plastic satchel and mold it around the item you wish to have chilled (just like an oversized ice-pack). When doing this you can avoid the mess/complications associated with direct application of your cooling mix to your container (with item to be chilled inside). This method is a good way to avoid contamination of your sample/drink/etc. with the ice bath liquid and to help stabilise the container that you are chilling. No mess, no fuss:). People with vacuum sealing equipment may wish to try this.

What is everyone's favourite cooling bath?

[nbk2000]

There was no need for two different threads about ice baths, so they've been joined. :)

[rooster]

ALENGOSVIG: I thought that more effective ice baths will allow you to make multi-step nitrations in fewer steps, for example TNT or TeNN. It can also serve other non-explosive purposes (in my case, for example neutralizing HNO3 with NaOH to make NaNO3. This gives off a lot of heat.

CaCl2 can be found in many different forms: the anhydrous form, the dihydrate, and the hexahydrate. I believe it is the hexahydrate that reacts endothermically with water, and the anhydrous that reacts exothermically.

Does anyone know how to make the two useful forms(anhydrous and hexahydrate)? Heating will be good, but how much heat and for how long will it be required to fully dehydrate it?
As for the hexahydrate, I guess it will just be to dissolve CaCl2 in boiling water, and collect the crystals when it chills?

[kingspaz]

both methods sound good to me. i would heat it at about 120*C and measure the mass of it every 15 minutes until there was no mass change. then you would know it had lost all the water it could at that temperature.