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pip
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[*] posted on 21-2-2011 at 14:06
garbage can chloroform


I want to make a liter to a liter and a half of chloroform and want to confirm my amounts as I fear I won't have enough water in the reaction. I have 10lbs calcium hypochlorite and wish to base everything off that.

in a 30+ gallon garbage can

10lbs calcium hypochlorite is 31.7 moles which is 63.4 moles hypochlorite which needs 570 moles water to make 10% hypochlorite or 10260 grams water.
3 moles hypochlorite to 1 mole acetone
20 moles acetone needed 1160 grams 1468ml
20 moles chloroform should be made 2380 grams or 1.6 liters
30lb ice is also required to keep cool but...

At this scale the reaction shouldn't be a problem but if my math is off it could get bad. Also keep in mind its very cold outside.
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Picric-A
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[*] posted on 21-2-2011 at 14:12


This seems like suicide to me, i can almost guarantee a runaway reaction (notorious with haloform reactions) which will send boiling acetone/steam/chloroform up at you.

How are you going to seperate the chloroform at the end? Got a 10litre RBF?
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peach
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[*] posted on 21-2-2011 at 15:31


This is quite a well known method of doing it dirty style.

Because the bucket is full of ice, the mixture is in direct contact with something freezing cold, and the chloroform has to bubble up through it to escape. Which means it's effectively got far better thermal contact with the ice than it would using a condenser.

If all goes to plan, his chloroform should be sat at the bottom of the bucket as a separate phase, so he'd only need to dry and distill that phase; the dirty, damp chloroform it's self.

I have wondered if this might actually be a better method of doing it at home, rather than in glass, due to the huge amount of freezing cold ice / water slush involved and the intimate contact that you won't get using glass.

Adding the reagents slowly at first might be an idea, and having excess ice handy. For instance, you might want to split in half or to a third and run it two or three times, such that if the first overheats, you have spare ice. If it's all going okay, you can proceed to run the others up. Rather than dump it all in with one go, have it get too hot, and lose it.

I'm sure I've seen someone called Cheapskate on one of these forums recently.

[Edited on 21-2-2011 by peach]




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[*] posted on 21-2-2011 at 15:53


I plan on surounding the can with snow and its below freezing outside so it'll be cold enough for sure with the ice. I also have a 2l sep funnel to use once I pour off most of the water. I know a 4l would be better but i'm sure I can prevent spills.

I'm trying to scale up chromic's correction of cheapskate's reaction but without adding hcl as the haloform is supposed to be basic
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[*] posted on 21-2-2011 at 16:07


The prep is a bit easier with Clorox Ultra, especially if you can freeze it in a chest freezer to slush. Then you can add all the acetone at once with vigorous stirring (paint mixer and drill). You won't have CaOH precipitate to deal with. 125ml acetone to 1.5 gallon jug gave me about 110ml yield.

[Edited on 2-22-2011 by Eclectic]
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[*] posted on 21-2-2011 at 17:41


Thanks for the suggestion about the chlorox but I already have the calcium hypochlorite.

But the question remains
1. will I have enough water
2. is calcium hypochlorite pure? mine is supposed to be but I thought I remebered that it is never more than 65%?
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[*] posted on 22-2-2011 at 02:02


Calcium hypochlorite maybe has some CaCl2 and Ca(OH)2 so it's not 100% pure.
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[*] posted on 23-2-2011 at 04:14


Watch this video before you attempt a haloform reaction in a trashcan.

http://www.youtube.com/watch?v=IdfHMz7WeXI

Even this gentleman who is a member here had a runaway using proper equipment to produce chloroform on a comparable scale.
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DJF90
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[*] posted on 23-2-2011 at 05:10


There are plenty of videos on youtube regarding the "trashcan synthesis" of chloroform. Filling the bin with ice and bleach, slow addition of the acetone, leaving the reaction to complete, decanting most of the aqueous phase off and finally separation and distillation seems to be the common approach.
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[*] posted on 23-2-2011 at 06:31


'Even this gentleman who is a member here had a runaway using proper equipment'
His gear is certainly nice, but without knowing what concentrations he was working with, it's hard to say how relevant his runaway is to the current case. In my experience (and as a rough rule of thumb),
- using 6% NaOCl solution nets you a 50C temperature rise
- using a 10% solution nets you (or would net you, absent boiling chloroform carrying off the heat) an 85C temperature rise

...but of course this is if you have no ice to absorb the heat by melting. As you can see, starting the reaction at room temperature without temperature control will get you quite a bit above the boiling point of chloroform, even with 6% bleach. With 6% bleach, you can get away with starting with ice cold reagents, even without ice (I have done this using -5C bleach and MEK... but don't use MEK, yields are bad). But the reaction is somewhat slow to start. At 10% you need ice, either by making a slushy of your reagents in a good freezer to start with, or by adding it later.
Alternatively I expect that if your condenser is good and your volumes not too large you could use the heat to distill the chloroform as it is produced (patents mention this too). Seems risky though, I don't plan to try it.
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[*] posted on 23-2-2011 at 06:45


Quote: Originally posted by slinky  
Watch this video before you attempt a haloform reaction in a trashcan.

http://www.youtube.com/watch?v=IdfHMz7WeXI

Even this gentleman who is a member here had a runaway using proper equipment to produce chloroform on a comparable scale.


I have seen that video, and wasn't going to mention it (lest I upset it's owner), but what it more clearly shows is nice glassware, as opposed to 'the proper' way to do something.

The flask is absolutely gigantic, the solutions concentrated and I'm guessing that first lot of acetone went in too fast.

Using large volumes means lower cooling rates, more concentrated solutions and rapid additions mean higher heat generation rates.

By using bins full of ice or slush in the solution it's self, more dilute solutions and slower addition rates, the temperature and rate of loss will come out lower.

This also shows why you can't scale something up by simply using bigger equipment. Larger animals, like elephants, have a harder time keeping cool because they have so much internal mass compared to their surface area.

A sphere does not have a lot of surface area compared to it's volume - in fact, it has the worst of all the geometric shapes as far as heating and cooling rates are concerned.***

Quote:
- using 6% NaOCl solution nets you a 50C temperature rise


Bartlog's point agrees with my experience as well. With more dilute domestic bleaches, the temperature rise is negligible.

A 50l reactor like that will set you back over $15k new. I know for a fact, he paid less than that for it, which is why he's using it. However, Eclectic pointed out above how he's gotten 100ml+ just freezing it to slush and mixing it with a paint paddle.

Spending more money does not always make something better, particularly when science is involved.

<iframe sandbox title="YouTube video player" width="640" height="390" src="http://www.youtube.com/embed/pdDC_as6F58" frameborder="0" allowfullscreen></iframe>

Neither does the surface area to volume ratio change in a linear fashion based on the size of your sphere;



***Anyone seen any tetrahedral bins around? :P In terms of transferring heat from the solution to the ice quicker, a cube would provide twice the surface area of 'melon ball' cubes. A cute point for those who like seeing seemingly not important laws happening in nature is that ice will round off it's corners as it melts, and approach a more spherical shape, because the corners also function as focal points for the heat energy; existing with three planes all connecting at one point. This is also true of people who hug the wall to skip cues, that they accelerate their experience by constricting their free dimensions.

[Edited on 23-2-2011 by peach]




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[*] posted on 23-2-2011 at 20:02


my Ice will really be snow so surface area check. be prepared to read a write up in an few weeks.
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